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Functionalized Ethylene Copolymers and Materials via Olefin Metathesis Polymerization

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Functionalized Ethylene Copolymers and Materials via Olefin Metathesis Polymerization
Creator:
BAUGHMAN, TRAVIS W.
Copyright Date:
2008

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Subjects / Keywords:
Alkenes ( jstor )
Carbon ( jstor )
Copolymers ( jstor )
Ethers ( jstor )
Macromolecules ( jstor )
Melting ( jstor )
Metathesis ( jstor )
Monomers ( jstor )
Polymerization ( jstor )
Polymers ( jstor )
City of Gainesville ( local )

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University of Florida
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University of Florida
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Copyright Travis W. Baughman. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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11/30/2006
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496613312 ( OCLC )

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FUNCTIONALIZED ETHYLENE COPOLYME RS AND MATERIALS VIA OLEFIN METATHESIS POLYMERIZATION By TRAVIS W. BAUGHMAN A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2006

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Copyright 2006 by Travis W. Baughman

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To Mom

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iv ACKNOWLEDGMENTS I would like to acknowledge my mother, Sarah Whetstone , and my sister, Tara Scozzaro, for the endless love and support a nd for being outstanding role models during my academic career. I also acknowledge Gene Baughman, Ina and Bob Porter, Dave Scozzaro, Luke Scozzaro, the McDaniel Family, as well as the late George P. Smith for guidance and support. During my time at the University of Florid a, I have had the privilege of working on the Butler Polymer Floor among scientists and students past and present that have made my time in Gainesville memorable. I thank Professors George Butler, Ken Wagener and John Reynolds for the creation and development of the Butler Polymer Floor, an enclave within the chemistry department allowing th e education of graduate students in an environment nurturing world renowned scientific research. I also thank Vic Thompson, Sara Klossner, Lorraine Williams, and Lori Clark for administrative assistance, and I especially recognize Jaydeep Mukherjee, Sreel a Mallick and the entire Florida Space Grant Consortium (NASA-FSGC) for three ye ars of generous s upport as a 2003 FSCG Fellow. The National Science Foundation and Army Research Office have also offered generous support throughout my graduate career. The introduction to scientific life at Cl emson University and academic advisement and course work under Professors Michael J. Drews, Gary Lickfield, and Michael Ellison were instrumental in my choice to continue on to graduate school, and I credit the years of undergraduate research experi ence with Professors Dennis W. Smith and Stephen H.

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v Foulger for my early development in the fi elds of polymer chemistry and materials science. There are a few graduate students I must acknowledge for the mutual time spent debating science on hood sashes, eating sligh tly repetitive lunches, and enjoying all things graduate school: Ben Reeves for smooth bass lines, team Ramrod, Kramer/Lilly dates, and the brown note; Jeremiah Tipt on, my RDS counterpart; Piotr Matloka for silicon help, proofreading this document, a nd potato distillate experiments; Florence Courchay for appealing discussions, BMB, and an introduction to southern France; Ryan Walczak for 322 debates, an introduction to stri ngs, and laboratory hygiene tutorials; Erik Berda for splitting the rent, ta lking Wagener group, and assist ance with stri ng theory. I also acknowledge some of the many colleague s and mentors along th e way including Bob Brookins, Tim Steckler, Jame s Leonard, Giovanni Rojas, Eveline van der Aa, Dr. Stephen ‘Ed’ Lehman, Dr. John C. Swor en, Dr. Timothy Ho pkins, Erik Nelson (Clemson), and Dr. Ping Jiang (Clemson). And la st but not least, I thank Helene “Lani” Cardasis and Joshua McClellan for the mutu al pondering of the perp etual question; what is fire?

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vi TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES.............................................................................................................xi LIST OF FIGURES..........................................................................................................xii LIST OF SPECTRAL DATA BY COMPOUND.............................................................xv ABSTRACT.....................................................................................................................xi x CHAPTER 1 INTRODUCTION........................................................................................................1 History of Olefin Metathesis........................................................................................2 Mechanistic Study of Olefin Metathesis...............................................................2 Metal Carbene Catalyst Development...................................................................5 Grubbs Ruthenium Catalysts.................................................................................6 Olefin Metathesis Polymerization................................................................................8 Acyclic Diene Metathesis Polymerization............................................................9 Ring-opening Metathesis Polymerization...........................................................10 Synthesis of Functionalized Polyethyle ne Copolymers via Olefin Metathesis..........12 ADMET Polymerization of , -dienes...............................................................13 ROMP Copolymerization of Cyclooctenes.........................................................13 Thermal Analysis of Polyethyl ene and Related Copolymers.....................................16 Sequenced Polyolefins via ADMET...................................................................20 Statistically Random Polyolefin s via ROMP Copolymerization........................26 Purpose of this Dissertation........................................................................................27 2 LINEAR ETHYLENE-ACRYLIC ACID COPOLYMERS VIA METATHESIS POLYMERIZATION.................................................................................................28 Introduction.................................................................................................................28 Experimental Section..................................................................................................30 Materials..............................................................................................................30 Instrumentation and Analysis..............................................................................30 Monomer Synthesis.............................................................................................31 A general procedure for acid protection.......................................................31 1-ethoxyethyl-2-(pent-4-enyl )hept-6-enoate (2-1).......................................32

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vii 1-ethoxyethyl-2-(oct-7-enyl )dec-9-enoate (2-2)..........................................32 1-ethoxyethyl-2-(undec-10-enyl)t ridec-12-enoate (2-3)..............................32 1-ethoxyethyl-2-(cyclo-4-oc tenyl)acetate (2-4)...........................................33 General procedure for free and acid protected ADMET polymerization.....33 Polymerization of 2-(4-pentenyl )-6-hepteneoic acid (2-5)..........................34 Polymerization of 2-1 (2-6)..........................................................................34 Polymerization of 2-2 (2-7)..........................................................................34 Polymerization of 2-3 (2-8)..........................................................................35 General conditions for Parr bomb hydrogenation........................................35 EAA9 (2-9): Hydrogenation of 2-5..............................................................35 EAA9 (2-10): Hydrogenation of 2-6............................................................36 EAA15 (2-11): Hydrogenation of 2-7..........................................................36 EAA21 (2-12): Hydrogenation of 2-8..........................................................36 General conditions for free acid ROMP copolymerization..........................36 For 15 mol% EAA (2-13).............................................................................37 For 9 mol% EAA (2-14)...............................................................................37 For 3 mol% EAA: (2-15).............................................................................37 Diimide hydrogenation procedure................................................................37 15% Acrylic Acid-Ethylene Copolym er (2-16): Hydrogenation of 2-13.....38 9% Acrylic Acid-Ethylene Copolymer (2-17): Hydrogenation of 2-14.......38 3% Acrylic Acid-Ethylene Copolymer (2-18): Hydrogenation of 2-15.......38 General conditions for protected acid ROMP copolymerization.................38 For 22.2 mol% EAA (2-19)..........................................................................39 For 13.3 mol% EAA (2-20)..........................................................................39 For 9.5 mol% EAA (2-21)............................................................................39 For 4.5 mol% EAA (2-22)............................................................................39 Hydrogenation of unsaturated ADMET and ROMP products.....................40 Parr bomb hydrogenation procedure............................................................40 ROMP EAA22.2 (2-23): Hydrogenation of 2-19.........................................40 ROMP EAA13.3 (2-24): Hydrogenation of 2-20.........................................40 ROMP EAA9.5 (2-25): Hydrogenation of 2-21...........................................40 ROMP EAA4.5 (2-26): Hydrogenation of 2-22...........................................40 Results and Discussion...............................................................................................40 ADMET and ROMP Monomer synthesis...........................................................40 Metathesis Polymerization of Acid Monomers...................................................41 Metathesis Polymerization of Hemi acetal Ester Protected Monomers...............42 Hydrogenation of Metathesis Products to Saturated EAA Copolymers.............44 Structural Analysis of EAA Copolymers............................................................45 13C and 1H NMR..........................................................................................45 Preliminary Small-Angle X-ray Scattering..................................................50 Thermal Analysis of Linear EAA copolymers....................................................52 Thermogravimetric Analysis...............................................................................54 Conclusions.................................................................................................................55

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viii 3 IONOMERS FROM SEQUENCED ETHYLENE-ACRYLIC ACID COPOLYMERS.........................................................................................................57 Introduction.................................................................................................................57 Experimental...............................................................................................................58 Materials..............................................................................................................58 Instrumentation and Analysis..............................................................................58 General Neutralization Procedure for Sequenced EAA Copolymers..................58 EAA21Zn25.................................................................................................59 EAA21Zn50.................................................................................................59 EAA21Zn75.................................................................................................59 EAA15Zn25.................................................................................................59 EAA9Zn25...................................................................................................59 Results and Discussion...............................................................................................59 Ionomer Design and Synthesis............................................................................59 Neutralization of Sequenced EAA Copolymers..................................................60 Ionomer Analysis........................................................................................................60 FT-IR Analysis....................................................................................................61 Thermal Analysis.................................................................................................62 Preliminary Secondary Structural Analysis.........................................................67 STEM analysis of EAA21Zn25...................................................................68 SAXS analysis of EAA21Zn25....................................................................69 Conclusion..................................................................................................................70 4 LINEAR ETHYLENE-VINYL ETHER COPOLYMERS: SYNTHESIS AND THERMAL CHARACTERIZATION........................................................................72 Introduction.................................................................................................................72 Experimental...............................................................................................................74 Materials..............................................................................................................74 Instrumentation and Analysis..............................................................................74 General Procedure for Grignard R eaction with Alkenyl Chlorides or Bromides..........................................................................................................76 1,12-tridecadiene-7-ol (4-1).........................................................................76 1,16-heptadecadiene-9-ol (4-2)....................................................................76 1,22-tricosadiene-12-ol (4-3).......................................................................77 General Alkylation Procedur e for the Preparation of , –Diene Ethers............77 7-methoxy-1,12-tridecadiene (4-4)..............................................................78 9-methoxy-1,16-heptadecadiene (4-5).........................................................78 12-methoxy-1,22-tricosadiene (4-6).............................................................78 7-ethoxy-1,12-tridecadiene (4-7).................................................................79 9-ethoxy-1,16-heptadecadiene (4-8)............................................................79 12-ethoxy-1,22-tricosadiene (4-9)................................................................80 General ADMET Polymerization Pro cedure for Symmetrical Ether Monomers........................................................................................................80 Polymerization of 7-methoxy-1,12-tridecadiene (4-10)...............................81 Polymerization of 9-methoxy-1,16-heptadecadiene (4-11).........................81

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ix Polymerization of 12-methoxy-1,22-tricosadiene (4-12).............................81 Polymerization of 7-ethoxy-1,12-tridecadiene (4-13)..................................82 Polymerization of 9-ethoxy-1,16-heptadecadiene (4-14).............................82 Polymerization of 12-ethoxy-1,22-tricosadiene (4-15)................................82 Hydrogenation of Unsaturated ADMET Polymers.............................................83 EMVE11 (4-16)............................................................................................83 EMVE15 (4-17)............................................................................................83 EMVE21 (4-18)............................................................................................84 EEVE11 (4-19).............................................................................................84 EEVE15 (4-20).............................................................................................84 EEVE21 (4-21).............................................................................................84 Results and Discussion...............................................................................................85 Polymer Design and Synthesis............................................................................85 Molecular Weight and Structural Analysis.........................................................86 13C and 1H NMR Analysis...................................................................................87 FT-IR Analysis....................................................................................................90 Thermal Analysis.................................................................................................92 Conclusion..................................................................................................................95 5 SEQUENCED COPOLYMERS OF ETHYLENE AND PROPYLENE: THE EFFECTS OF SHORT ET HYLENE RUN LENGTHS.............................................97 Introduction.................................................................................................................97 Experimental Section..................................................................................................99 Materials..............................................................................................................99 Instrumentation and Analysis..............................................................................99 Synthesis of EP7 Copolymer.............................................................................100 Diethyl-2-(but-3-enyl) malonate (5-1).......................................................100 1,6-(Diethyl-2-(but-3-enyl)malonyl) hexane (5-2).....................................101 2,9-(But-3-enyl)-2,9 -dicarboxysebacic acid (5-3)......................................102 2,9-(But-3-enyl)sebacic acid (5-4).............................................................102 2,9-(But-3-enyl)-1,10-d ecanediol (5-5)......................................................103 5,12-Dimethyldodeca-1,15-diene (5-6)......................................................103 Polymerization of 5,12-dimethylhexadeca-1,15-diene: EP7u (5-7)...........104 EP7 (5-8)....................................................................................................105 Synthesis of EP5 copolymer..............................................................................106 1,4-(diethyl-2-allylmalonyl) butane (5-9)..................................................106 2,7-diallyl-2,7-dicarboxysuberic acid (5-10).............................................106 2,7-diallylsuberic acid (5-11).....................................................................107 2,7-diallyl-1,8-octanediol (5-12)................................................................107 4,9-Dimethyldodeca-1,11-diene (5-13)......................................................107 Polymerization of 4,9-dimethyldodeca-1,11-diene: EP5u (5-14)..............108 EP5 (5-15)..................................................................................................108 Results and Discussion.............................................................................................109 Polymer Design and Synthesis..........................................................................109 Molecular Weight and Structural Analysis.......................................................112 Structural Analysis: 13C NMR...........................................................................113

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x Structural Analysis: 1H NMR............................................................................117 Structural Analysis: FT-IR................................................................................118 Thermal Analysis: DSC.....................................................................................120 Conclusion................................................................................................................127 APPENDIX 1H AND 13C NUCLEAR MAGNETIC RESONANCE SPECTRA FOR SELECTED INTERMEDIATES AND TARGET MATERIALS.129 Compounds Described in Chapter 2.........................................................................129 Compounds Described in Chapter 4.........................................................................142 Compounds Described in Chapter 5.........................................................................163 LIST OF REFERENCES.................................................................................................172 BIOGRAPHICAL SKETCH...........................................................................................183

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xi LIST OF TABLES Table page 1-1 Thermal characterization data for sequenced ethylene copolymers...........................21 2-1 Molecular weight data for ADMET and ROMP unsaturated free acid copolymers..42 2-2 Molecular weight data for protected, unsaturated copolymers...................................44 2-3 Characterization data fo r sequenced EAA materials..................................................45 4-1 U.S. Patents pertaining to ethyleneco -vinyl ether materials.....................................73 4-2 Characterization data fo r sequenced EVE copolymers..............................................86 4-3 Thermal analysis data for sequenced EVE copolymers.............................................93 5-1 Polymer Characterization Data.................................................................................113

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xii LIST OF FIGURES Figure page 1-1 Olefin metathesis reactions...........................................................................................1 1-2 Chauvin mechanism.....................................................................................................4 1-3 Schrock’s tungsten a nd molybdenum Catalysts...........................................................6 1-4 Grubbs 1st and 2nd generation ruthenium me tathesis catalysts.....................................7 1-5 ADMET mechanism...................................................................................................10 1-6 Abbreviated ROMP mechanism using cyclopentene.................................................11 1-7 Metathesis polymerization-hydrogena tion methodology for ethylene copolymers...12 1-8 Description of commercial radical c opolymerization including structural features created during the polymerization process...............................................................13 1-9 Reported cyclooctene monomers the bottom row has been copolymerized with cyclooctene in various experiments.........................................................................14 1-10 Expected ethylene seque nce length distributions for ROMP polymerization of 5cyclooctenes.............................................................................................................15 1-11 Second heating cycle DSC scans of commercial polyethylene samples at 10oC/min...................................................................................................................17 1-12 Second heating cycle DSC scan of commercial carboxylic acid copolymers (Nucrel™) and ionomers (Surlyn™) at 10oC/min...................................................19 1-13 Melting profiles of saturated ADMET polymers with a 9 carbon branch frequency..................................................................................................................22 1-14 Melting profiles of saturated ADMET polymers with a 15 carbon branch frequency..................................................................................................................24 1-15 Melting profiles of saturated ADMET polymers with a 21 carbon branch frequency..................................................................................................................25 2-1 Three modes of EAA copolymer synthe sis and alternative c opolymer structures.....29

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xiii 2-2 Synthesis of protecte d ADMET and ROMP monomers............................................41 2-3 EAA copolymer synthesis via ADMET.....................................................................43 2-4 EAA copolymer synthesis via ROMP........................................................................43 2.5 13C NMR tracking the conversion of the protected monomer to unsaturated copolymer to saturated, free acid copolymer EAA21 ..............................................47 2-6 FT-IR analysis of hydrogenation-depr otection reaction from unsaturated polymer 2-8 to copolymer EAA21 ( 2-12 )..............................................................................49 2-7 SAXS analysis of melt pressed and drawn EAA21 ...................................................51 2-8 DSC overlay for ADMET EAA copolymers..............................................................53 2-9 DSC overlay for ADMET EAA copolymers..............................................................54 2-10 Thermogravimetric analysis of EAA copolymer series...........................................55 3-1 Sequenced EAA ionomer synthesis............................................................................60 3-2 First cycle heating curves for DSC of ADMET free acid and ionomer materials after storage at room temp erature for two months...................................................64 3-3 Second cycle heating curves for the DSC of ADMET free acid and ionomer materials...................................................................................................................65 3-4 Thermogravimetric analysis of Nucrel™ and Surlyn™ EMAA materials................66 3-5 Thermogravimetric analysis for sequenced EAA21 ionomers and the parent EAA21 copolymer...................................................................................................67 3-6 STEM images for EAA21Zn50 .................................................................................68 3-7 Comparison of SAXS scattering profile s for commercial materials (Nucrel™ and Surlyn™) and sequenced analogs ( EAA21 and EAA21Zn50 )...............................70 4-1 Synthesis of EVE copolymers....................................................................................86 4-2 13C NMR progression from monomer to target EVE copolymer...............................88 4-3 FT-IR analysis of EVE copolymers:..........................................................................91 4-4 DSC second heating and cooling scans for six sequenced EVE copolymers.............94 5-1 DSC thermograms of previous ly synthesized EP copolymers.................................110 5-2 ADMET monomer synthesis....................................................................................111

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xiv 5-3 EP7 copolymer synthesis.........................................................................................112 5-4 13C NMR analysis following monomer to copolymer for both EP5 (left) and EP7 (right)......................................................................................................................11 4 5-5 13C NMR endgroup analysis of EP7 ........................................................................116 5-6 1H NMR analysis following monomer 5-6 to EP7 sequenced ethylene-propylene copolymer...............................................................................................................118 5-7 FT-IR analysis for sequenced EP copolymers: a) EP5 , b) EP7 ...............................119 5-8 DSC analysis: seconding heating scan of EP5 and EP7 ..........................................122 5-9 DSC curves for annealing experiments on EP7 .......................................................125

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xv LIST OF SPECTRAL DATA BY COMPOUND Data page 2-(4-pentenyl)-6-hepteneoic acid O OH 33..............................................................129 2-(7-octenyl)-9-deceneoic acid O OH 66..................................................................130 2-(10-undecenyl)-12-trideceneoic acid O OH 99.....................................................131 2-(4-cyclooctenyl)acetic acid O OH ................................................................132 1-ethoxyethyl-2-(4-pentenyl)-6-hepteneoate O O 33 O .......................................133 1-ethoxyethyl-2-(7-octenyl)-9-decenoate O O 66 O .............................................134 1-ethoxyethyl-2-(10-undecenyl)-12-trideceneoate O O 99 O ..............................135 1-ethoxyethyl-2-(4-cyclooctenyl)acetate O O O .............................................136 Polymerization of 1-ethoxyethyl -2-(4-pentenyl)-6-hepteneoate 3 3 n O O O ......137

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xvi Polymerization of 1-ethoxyethyl-2-(10-undece nyl)-12-tridecenoate 9 9 n O O O 138 EAA9 n OH O ....................................................................................................139 EAA15 OH O ......................................................................................140 EAA21 OH n O ........................................................................141 1,12-tridecadiene-7-ol OH 4 4................................................................................142 1,16-heptadecadiene-9-ol OH 6 6...........................................................................143 1,22-tricosadiene-12-ol OH 9 9...............................................................................144 7-methoxy-1,12-tricosadiene OCH3 4 4....................................................................145 9-methoxy-1,16-heptadecadiene OCH3 6 6................................................................146 12-methoxy-1,22-tricosadiene OCH3 9 9...................................................................147 7-ethoxy-1,12-tridecaadiene OCH2CH3 4 4.....................................................................148 9-ethoxy-1,16-heptadecadiene OCH2CH3 6 6..................................................................149 12-ethoxy-1,22-tricosadiene OCH2CH3 9 9......................................................................150 Polymerization of 7-methoxy-1,12-tridecadiene OMe 4 4 n ...............................151

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xvii Polymerization of 9-methoxy-1,16-heptadecadiene OMe 6 6 n ..............................152 Polymerization of 12-methoxy-1,22-tricosadiene OMe 9 9 n ..................................153 Polymerization of 7-ethoxy-1,12-tridecadiene OEt 4 4 n .......................................154 Polymerization of 9-ethoxy-1,16-heptadecadiene OEt 6 6 n .................................155 Polymerization of 12-et hoxy-1,22-tricosadiene OEt 9 9 n .....................................156 EMVE11 n OMe ...............................................................................................157 EMVE15 OMe ........................................................................................158 EMVE21 OMe ............................................................................159 EEVE11 n OEt ................................................................................................160 EEVE15 OEt ..........................................................................................161 EEVE21 OEt .............................................................................162 Diethyl-2-(but-3-enyl) malonate OEt EtO O O .............................................................163 1,6-(Diethyl-2-(but-3-enyl)malonyl) hexane O O OEt EtO OEt EtO O O ..................164 2,9-(But-3-enyl)sebacic acid O HO OH O ............................................165

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xviii 2,9-(But-3-enyl)-1,10-decanediol HO OH .....................................166 5,12-Dimethyldodeca-1,15-diene CH3 CH3 .........................................167 EP7u from 5,12-Dimethyldodeca-1,15-diene CH3 CH3 n .................167 EP7 CH3 n ........................................................................................................167 1,4-(diethyl-2-allylmalonyl) butane O O HO OH ............................................168 2,7-diallyl-1,8-octanediol HO OH ..............................................................169 4,9-Dimethyldodeca-1,11-diene CH3 CH3 ......................................................170 EP5u from 4,9-Dimethyldodeca-1,11-diene CH3 CH3 n ................................170 EP5 CH3 n ...............................................................................................................171

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xix Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy FUNCTIONALIZED ETHYLENE COPOLYME RS AND MATERIALS VIA OLEFIN METATHESIS POLYMERIZATION By Travis W. Baughman May 2006 Chair: Kenneth B. Wagener Major Department: Chemistry Copolymers of ethylene with acrylic acid, propylene, and alkyl vinyl ethers were synthesized by a well-known olefin metath esis polymerization-hydrogenation approach enabling the preparation of three unique groups of sequenced ethylene-based materials including ethylene-co-acrylic acid (EAA), ethylene-co-methyl vinyl ether (EMVE), ethylene-co-ethyl vinyl ether (EEVE), and ethylene-co-propylene (EP) materials. Applying acyclic diene metathesis ( ADMET) polymerization of symmetrical , -dienes, unsaturated copolymers were isolated th at, upon exhaustive hydrogenation, were converted to ethylene copolym ers with pendant functionality evenly spaced along the polymer backbone. This approach grants absolute control ethyle ne sequence length distribution, functional group identity, a nd pendant branch concentration producing pristine copolymer microstructures, and th e effects on polymer mo rphology are apparent upon structural analysis by 1H and 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) absorbance, as we ll as thermal analysis using differential

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xx scanning calorimetry (DSC) and thermograv imetric analysis (TGA). The research presented in this dissertation is significan t to the development of structure-property relationships for widely applied commodity polyolefin materials as well as the application of the recently recognized olefin metathesis reaction to the preparation of highly ordered macromolecules displaying uniqu e material properties based on absolute synthetic control over polymer microstructure. Chapter 2 reports the application of ADMET and the ring-opening metathesis (co)polymerization (ROMP) of functionali zed cyclooctenes and cyclooctene to the preparation of a family of EAA copolymer s generating both sequenced EAA copolymers and statistical materials bear ing randomly placed carboxylic acid functionality prepared at analogous molar compositions of acrylic ac id. Ionomers reported in Chapter 3 from sequenced ADMET EAA materials described in Chapter 2 repr esent the first report of any type of ethylene-co-acrylic acid ionomers produced applying olefin metathesis polymerization. As with free acid copolymer s, striking differences thermal behavior and x-ray scattering patterns relative to pare nt acid polymers and commercial ionomers indicate novel ionomeric mo rphologies also supported by infrared absorbance and preliminary scanning transmission electron micrographs. Chapter 4 describes the preparation of six EMVE and EEVE copolymers applying ADMET methodology detailing what is believed to be the first sy nthesis and structure-prope rty analysis of such materials. In closing, Chapter 5 describe s the preparation of tw o highly-branched, yet sequenced, EP materials in the extension of earlier sequenced EP copolymer research applying a new monomer synthe sis facilitating the creation of shorter ethylene run lengths and higher branch cont ents in ADMET materials.

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1 CHAPTER 1 INTRODUCTION The pursuit of the mechanistic understanding of olefin metathesis as well as the production of novel, more practical transition me tal catalysts has driven the prevalent use of this mild carbon-carbon double bond scrambling reaction1 and earned the 2005 Nobel Prize in Chemistry for Robert H. Grubbs, Richard R. Schrock, and Yves Chauvin for their collective effort in the field.2, 3 A brief historical overvie w of the discipline follows describing the early mechanistic studies, th e development of homogeneous metal-carbene complexes, and the application of the various modes of olefin metathesis to a myriad of synthetic bottlenecks (Figure 1-1). R R R R' R R' Ring-Closing Metathesis (RCM) R' R R R' Ring-Opening Metathesis (ROM) Cross Metathesis (CM) R Ring-Opening Metathesis Polymerization (ROMP) Acyclic Diene Metathesis (ADMET) Polymerization R R R n n R R R R' 1 : 2 : 2 : 1 Figure 1-1. Olefin metathesis reactions

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2 Sufficient review articles exist detailing the recent synthetic advances in olefin metathesis4, 5 including polymer chemistry by acyclic diene metathesis (ADMET),6, 7 ring-opening metathesis polymerization (ROMP),8, 9 and small molecule chemistry using ring-closing metathesis (RCM),10, 11 cross-metathesis (CM),12, 13 and ring-opening metathesis (ROM) reactions.14, 15 This chapter will focus on the application of ADMET and ROMP chemistry to the synthesis of unsaturated and saturated polyethylene copolymers. Fundamental stru ctural differences between metathesis copolymers and traditionally synthesized ethylene copolymers will be discussed, as well as the morphological consequences of ethylene seque nce length distribution and pendant branch frequency as revealed by differe ntial scanning calorimetry. History of Olefin Metathesis Mechanistic Study of Olefin Metathesis Industrial research during the 1950s drove the development and understanding of many fundamental synthetic polymer techni ques, including the burgeoning of a new synthetic field invol ving reactions of carbon-carbon doubl e bonds. Initial reports of olefin metathesis using high-oxidation state metal catalyst mixtures exist throughout the literature of the late 1950s and early 1960s,16-21 but while reactions of propylene produced unsaturated polymeric compounds a nd numerous small molecule olefins, ethylene polymerizations were not effective using similar catalyst systems, perplexing chemists of the time. While polymerizati on experiments continued using ill-defined heterogeneous mixtures of mo lybdenum catalysts and activa ting agents such as alkyl aluminum, Ziegler-Natta molybdenum catalysts were being employed as ROMP initiators in the polymerization of various cyclic olefins. It was also discovered olefin metathesis

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3 using ruthenium and rhenium compounds was possible without the addition of activating alkyl aluminum species. The first related patent arising in 1957 from a DuPont chemist Herbert Eleuterio reports the reaction of propylene with a MoO3/Al2O3 catalyst bed producing an ethylenepropylene copolymer and various gaseous –olefins.16 A number of reports surfaced reporting similar transformations around the same time,17-21 but little in the literature granted insight into the mechanistic detail s of the transformation. It was Nissim Calderon’s discovery of ROMP using a WCl6 catalyst mixture where he recognized that the disproportionation of olefins was respons ible for the producti on of polyalkeneamer products22, 23 and unsaturated small molecules.24, 25 He then coined the term “olefin metathesis” and continued the explanation of this transformation in a later article, although his proposal of a metal complexed cy clobutane intermediate was later proven incorrect.23 While experiments continued on vari ous substrates in industrial labs throughout the world, a concurrent realizat ion of the chemical transformation was reached by Johannes Mol in the Netherlands while performing isotopically labeled propylene polymerization experiments.26 The early 1970s produced numerous reports de tailing mechanistic f eatures of olefin metathesis from experimental and theoretical approaches using a wide variety of catalyst species, most of which fail to accurately describe the currently accepted mechanism suggested by Yves Chauvin in 1971.27 Although Calderon’s analysis of numerous metathesis reactions lead to his correct st ructural analysis of reaction products and suggestion of double-bond rearrangement, many que stions remained concerning catalytic intermediates, particularly, th e identity of the active species responsible for the chemical

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4 transformation. Upon comparison of three repo rts of the time, the similarity between the propylene disproportionation from Banks and Bailey at Phillips, Inc.19 and ring-opening polymerization of cyclopent enes reported by G. Natta28 in the context of E. FischerÂ’s recently reported tungsten carbene complex29 allowed Chauvin to propose mechanism depicted in Figure 1-2. Although this theory was supported by most scientists at the time, the debate continued throughout the following years of research, and, as with most cutting edge research, ChauvinÂ’s proposal n eeded time and experimental evidence before it became the widely accepted mechanism of olefin metathesis among the plethora of incorrect proposals of the 1970s. Figure 1-2. Chauvin mechanism Thomas Katz made a significant contribution to the field with his first report on the subject in 1975 supportin g ChauvinÂ’s mechanism,30 one of the few reports even mentioning the three-year-old proposal. In this seminal report, Katz describes the relationship of the star ting olefin(s) and the obs ervation that, after reaction with the metal center, two unique olefins can be pr oduced upon retro cyclization of the metallocyclobutane. In this case, structural and/or electronic diffe rences in the starting olefin(s) yield statistical di stributions of products based on stability of the catalytic intermediate. Using this analysis, he also projected the possibility of reaction control

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5 allowing production of single compounds or multiple olefinic products in the same reaction. Katz credits Calderon for the initia l report, but notes he could not explain the presence of multiple olefinic species in produc t mixtures. Katz was a true visionary in the field not only resolving th e mechanism debate, but proj ecting novel app lications of the reaction well before their time, paving th e road for future catalyst developments.30 Grubbs was also quick to rationalize the me tal carbene, proposing this as the active species just after Katz in 1975. His approach to prove the mechanism involved the use of isotopically labeled olefins to track reaction pathways, thereby, allowing more in-depth structural analysis of product mixtures and determination of catalytic pathways.31 Katz and other researchers continued research involving stable metal carbenes, but most were unsuccessful in promoting olefin metathesis. These developments, however, did lead to the preparation of the first reported metal-car bene species by Katz in 1976 that was able to initiate the ROMP of cy clopentenes and cyclooctenes.32, 33 As work in the field rapidly increased, catalyst development gained momentum as the convergence of polymer chemistry and organometallic catalysis was being more widely recognized. Metal Carbene Catalyst Development The first report of a tantalum carbene co mplex by Richard Schrock in 1974 began the drive for homogenous metathesis catalysis synthesis still devel oping today, although there is no mention the relevance of this complex to olefin metathesis.34 While many Fischer metal carbenes of low oxida tion state metals were being produced35, 36 and had been applied by Katz in a successful meta thesis reactions, the limitations of these catalysts were apparent to Schrock who began the synthesis of high oxidation state metal carbenes that referred to as metal alkylidenes , since referred to as Schrock carbenes in honor of his work. Tantalum and niobium carbenes developed by Schrock at DuPont

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6 allowed production of isolable complexes a nd were reported as the first metal-carbene species shown to undergo the olef in metathesis by reaction with cis-2-pentene.37 The catalytic activity of such tantalum compounds was low at best, and further catalyst synthesis using tungsten and molybde num carbenes followed (Figure 1-3). CH3 CH3 Mo N O O F3C F3C CH3 F3C F3C H3C CH3 CH3 W N O O F3C F3C CH3 F3C F3C H3C Figure 1-3. SchrockÂ’s tungs ten and molybdenum catalysts The isolation of novel meta l alkylidene complexes not only began exposing the electronic differences in the two types of metal carbenes, 8 but allowed the production of highly active, homogeneous metathesis catalysts. Noting the increased catalytic activity of these complexes, researchers began appl ying these well-defined metal carbenes to more and more reactions demonstrating the potential widespread application of these transformations, but the highly electroph ilic and oxophyllic metal centers created limitations of inert reaction conditions and low functional group tolerance. While development of novel high-oxidation state catal ysts continued, GrubbsÂ’ focus shifted to low oxidation state ruthenium carbenes that ulti mately lead to the widespread application of the reaction in nearly ever y area of synthetic research. Grubbs Ruthenium Catalysts GrubbsÂ’ first work in the field of olefin me tathesis was as a postdoctoral researcher probing the active specie s of the transformation in test reactions using the inherently unstable, yet highly functional metathesis co mplexes of the time. The high oxidation state metal center was the focus of his work as it was responsible for promoting

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7 metathesis, but also led to fast catalyst d ecomposition in the presence of trace impurities or common polar functional groups. The recognition of RuCl3 mediated ROMP of a strained cyclic olefin under certain conditions lead Grubbs Â’ synthetic effort into the preparation of the first highly ac tive ruthenium (II) catalysts around 199238-40 (Ru1, GrubbsÂ’ first generation catalyst) exhibiting greatly enhanced functional group tolerance of compared to any current system of the era. In particular, Ru1 (Figure 1-4) and similar compounds were interesting to the catalyst community because the ruthenium carbene exhibited features common to both Fischer a nd Schrock carbenes but were not correctly classified as either one. Th is created the novel way of thinking in that low and high oxidation state metals display a continuum of electronic features, and the alteration of catalyst sterics and/or electr onics via metal selection and ligand attachment could allow production of new, more pract ical catalysts through s ynthetic modification. A variety of ligands for ruthenium carbenes were prepared and studied to determine electronic and steric effects of catalyst modification, but the synthesis of GrubbsÂ’ second generation catalyst (Ru2) by the exchange of the N-he terocycle carbene (NHC) ligand with one of the phosphine ligands in Ru1 created the highest activity for a ruthenium catalyst to date (Figure 1-4).41, 42 Ru PCy3Cl Cl PCy3 Ru PCy3 Cl Cl N N Ru1Ru2 Figure 1-4. Grubbs 1st and 2nd generation ruthenium metathesis catalysts

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8 Although it seemed Ru2 forecasted the end of high-oxidation state metal metathesis catalysts due to comparable activity as well as excellent functional group tolerance,43-45 the realization of competing ol efin metathesis and olefin is omerization reactions created questions concerning in depth mechanistic detail s of the reaction. The recent isolation of a bimetallic ruthenium hydride catalyst decomposition product46 intrigued researchers, and could be the culprit causing olefin is omerization commonly observed when using Ru2.47-49 Of course, chemists have exploited the notion of facile in situ metal hydride preparation to perform tandem metathesis-isomerization49 or metathesis-hydrogenation50 reactions in one pot, but, through continued academic51 investigation and development of industrial scale cata lyst synthesis with Materia, Inc.,52 Grubbs continues to drive the development of novel catalysts focused on reducing the limitations of ruthenium metathesis. Currently, industry research is focused on applying this versatile transformation to many synthe tic challenges solving curr ent synthetic problems in pharmaceutical, polymer, and petrochemical pro ecsses spearheading the return of olefin metathesis to the industrial setting where rese arch was initiated nearly 50 years ago. Olefin Metathesis Polymerization The application of olefin metathesis to polymer chemistry through ADMET and ROMP transformation has solved many synthe tic issues for macromolecular chemists allowing the production of many systems unattainable using well-known polymer synthesis and modification. This section of the introduction will di scuss the application of olefin metathesis to polymer chemistry and the key differences between the two polymerizations concerning kinetic and th ermodynamic considerations. Extensive literature exists detailing the ADMET and RO MP of various unsaturated compounds, but the intent of the following text is to desc ribe the relationship a nd application of these

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9 polymerization techniques to the preparation of functionalized polyethylene materials and copolymers. Acyclic Diene Metathesis Polymerization Acyclic diene metathesis (ADMET) is the conversion of a linear diolefin compound to an unsaturated polymer through the repetitive cross metathesis reaction producing ethylene as a byproduct (Figure 1-1),53-58 The recent catalyst developments have allowed great flexibility in the ident ity of the R group of the diolefin allowing production of many polymers with a polyethyl ene backbone bearing pendant groups like chiral amino acids and peptides,59-62 reactive chloroand alkoxy silanes,63-67 as well as numerous examples of sequenced ethylene-olefin copolymers.68-74 The functional group tolerance of newer catal yst systems has driven the application of ADMET allowing production of many highly functionalized copol ymers with thermally stable hydrocarbon backbones.6 The mechanism of ADMET is very similar to any olefin metathesis reaction, but the equilibrium involved requires careful reac tion setup to afford high molecular weight products using this methodology. Fi gure 1-5 displays the ADMET mechanism illustrating the necessity of ethylene condensate removal, thereby, driving the equilibrium reaction to the polymer. An important feat ure of ADMET is the active catalyst species, the free methylidene, is only produced after th e initial metathesis cycle. The benzilydene catalyst first reacts with m onomer releasing styrene (for Ru1 or Ru2) while producing a new metal alkylidene species. Upon reacti on with another monomer unit and formation of the metallocyclobutane, retro 2+2 addition releases the methylid ene catalyst and one dimer molecule. The newly liberated methy lidene then reacts with another monomer, releasing ethylene and reforming the metal alkyl idene. The cycle continues as polymer is

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10 constructed through a stepwise addition of m onomer creating dimer, then trimer, then tetramer, etc. Figure 1-5. ADMET mechanism This type of polymer buildup is typical to all step-growth processes yielding polydispersities near 2.0 also requiring monomer conversions over 95% to achieve high molecular weight products.75 Here, monomer purity, catal yst lifetime, and functional group tolerance play a significant role in th e applicability of ADMET to any type of polymer synthesis, and even though SchrockÂ’s catalysts ar e still readily applied to ADMET synthesis, ruthenium catalysis ha ve allowed the preparation of many functionalized materials using monomers in compatible with the high oxidation state metals.6 Ring-opening Metathesis Polymerization Ring-opening metathesis polymerization (R OMP) is the conversion of strained cyclic olefins to unsaturated polymers (Figur e 1-1). This reaction is similar to ADMET

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11 polymerization in mechanism, but here, the catalyst species is bound to the polymer chain end upon initiation and throughout the polymer ization with no production of ethylene during the reaction (Figure 1-6) . In this sense, the chain-addition nature of this polymerization ROMP is a completely differe nt process from the thermodynamic stepgrowth chemistry involved in ADMET polymerization. Ln Ru Ph initiator Ru Ln initiated polymer chain Ph Ph R n unsaturated ROMP product R R H R Figure 1-6. Abbreviated ROMP mechanism using cyclopentene ROMP is a kinetically driven reaction that relies on the releas e of ring strain of cyclic olefins to drive the polymerization. The metal alkylidene in itiator, once reacted with monomer in a 2+2 olefin and metal-car bene cyclization, forms a metallocyclobutane that undergoes a ROM reaction leaving the newly formed me tal alkylidene. The active catalyst species remains bonded to the initiated polymer ch ain end and continues the reaction with new monomer in turn addi ng monomer sequentially to the polymer reproducing a reactive chain end every ROM step. Polymerization in this manner allows the preparation of high molecular weight ma terials in short reaction times, and chain addition chemistry allows the synthesis of a myriad of functional polymers and designer materials76, 77 by polymerization of various unsaturated cyclic olefin like cyclopentenes, cyclooctenes, and norbornenes.8

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12 While catalyst control and polydispersity may be difficult to control during many chain polymerization processes, the mild metathesis reaction produces few, if any, structural defects during olefin metathes is allowing preparati on of many functional macromolecules as well as monodi sperse polymers via living ROMP9 accessible using various molybdenum catalysts78, 79 or ruthenium complexes.80-82 This further illustrates the versatility of olefin metathesis, and the fact that the exact sa me olefin metathesis catalyst can perform both step-growth polym erization as a true catalyst and chainaddition polymerization as an initiator is a test ament to the widespread application of this transformation for the production of specific macromolecular structures as well as the large scale synthesis of commodity materials.83 Synthesis of Functionalized Polyethylene Copolymers via Olefin Metathesis Olefin metathesis can be used to prep are many types of unsaturated copolymers that, upon subsequent exhaustive hydrogenati on, resemble copolymers of ethylene and various polar vinyl monomers (Figure 1-7). [H] R n R n n x y R ADMET or ROMP product saturated polymerethylene copolymer Figure 1-7. Metathesis polymerizatio n-hydrogenation for ethylene copolymers Although simple in application, this s ynthetic methodology enables the preparation of a wide variety of novel polyethylene based materials with specific structural features unattainable using current chain copolymerization techniques where rampant side reactions lead to unwanted br anching and random incorporati on of functionality (Figure 1-8). While ADMET allows the precise placem ent of pendant functionality and creation of a monodisperse distribution of ethylene r un lengths throughout a range of comonomers

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13 and comonomer ratios, ROMP allows the pr eparation of statistically functionalized materials exhibiting minimum run length dist ributions through the copolymerization of functionalized cyclic alkenes with cyclic olefins. Figure 1-8. Description of commercial radical copolymeri zation including structural features created during th e polymerization process ADMET Polymerization of , -dienes The preparation of sequenced ethyle ne copolymers via ADMET requires the synthesis of appropriately functionalized symmetrical dienes to perform the aforementioned polymerization-hydrogenation reactions. An assortment of ADMET monomers has been prepared applying vari ous synthetic technique s allowing creation of a wide variety of possible polymer structures.6, 7 Here, the flexibility of ultimate saturated copolymer structure and pendant group identity is solely dependant on catalyst compatibility or the use of protecting group st rategies as applied in Chapter 2 to the synthesis of EAA copolymers. Further disc ussion concerning polymer structure is included in the thermal analysis section of this introduction. ROMP Copolymerization of Cyclooctenes Unlike ADMET, ROMP utilizes the ring st rain of small cyclic compounds like cyclooctene to drive the ch ain-addition polymerization.84 Cyclooctene and functionalized cyclooctene derivatives were copolymerized to yield linear, random copolymers (Figure 1-9). These unsaturated c opolymers were then converted to model copolymers of

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14 ethylene and acrylic acid via exhaustive hydrogenation. This reaction saturates all remaining olefin in the polymer affording a copolymer with carboxylic acid functionality distributed randomly along the chain. Co monomer feed ratios were adjusted for production of copolymers with varying degrees of functionality. A lthough reactivity of structurally different cyclooctenes in ROMP is slightly different, Grubbs85 and various others86-88 have indicated statistically random in corporation of com onomers is still achieved. Figure 1-9. Reported cyclooc tene monomers the bottom row has been copolymerized with cyclooctene in various experiments As sequence lengths are directly cont rolled via ADMET polymerization, the ROMP of asymmetric cyclic olefins creates a distribution of ethylene sequence lengths dependant on monomer structure. Figure 110 illustrates the hom opolymerization of a substituted cyclooctene, whereby, variable se quence length distributions are created due to a dependence on monomer orientation when adding to the polymer chain end. In the top reaction, monomers both add in a head-t ail fashion producing a seven carbon distance between branch points. This reaction can also occur in and head-to-head sense or a tailto-tail addition installing run lengths of 6 and 8 car bons, respectively, as depicted in the bottom two monomer additions. Statistically, these three reac tions occur in a 2:1:1 ratio

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15 producing an average run length of seven carbon s for this particular polymer. This distribution of sequence lengths is significant, especially when applied to ethylene copolymer synthesis. Figure 1-10. Expected ethylene sequence leng th distributions for ROMP polymerization of 5-cyclooctenes Upon ROMP copolymerization of a 5-subs tituted cyclooctene with cyclooctene,85, 87, 88 the distribution of sequence lengths becomes slightly more complex as all previously mentioned addition can occur al ong with the random incorporation of 8 carbons into the polymer back bone by addition of one unit of cyclooctene. This creates a complex distribution of ethylene run lengt hs throughout the material as previously described leading to distribution of run lengths of [1 (6 + 8(1,2, 3Â…) : 2 (7 + 8(1,2,3Â…) : 1 (8 + 8(1,2,3Â…)]. Although these materials are referred to as statistically random copolymers, the nature of ethylene run lengths is such that functionality is spread

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16 throughout the copolymer with pendant groups only as close as six carbons to each other. Structurally, these copolymers resemble ra dically copolymerized ethylene copolymers, but the limitation of run length due to the more uniform distribution has significant effects on thermal behavior. Thermal Analysis of Polyethyle ne and Related Copolymers Copolymerization of ethylene and vari ous vinyl comonomers has been of significant interest in the past fifty years,89 and many proprietary processes have been developed to access various manifestations of ethylene-based materials through incorporation of polar func tionality, thereby, generati ng novel materials performance from commodity polymers.90, 91 Specific control over se quence length distribution by incorporation of pendant branch units presen t in comonomers allows access to various levels of polymer crystallinity drastically affecting bulk material properties. A DSC overlay in Figure 1-11 represents the typical melting pr ofiles for polyolefin copolymers illustrating the ability to tune thermal behavior such as melting and recrystallization profiles fo r commercial low-density (Tg= 61oC, Tm= 113oC, Hm= 82 J/g), high-density (Tm= 133oC, Hm= 203 J/g), and ultra-high molecular weight (Tm= 135oC, Hm= 157 J/g) polyethylene. Melting poin t clearly shifts to higher peak temperatures as polymer structure is cha nged from a randomly branched system to a high-molecular weight, linear polymer to an even higher molecular weight material exhibiting the dependence of polymer microstr ucture on chain packing and, ultimately, crystallization. As expected, the more high ly-branched low-density polyethylene exhibits a lower peak melting point and heat of fusion due to irregular branch frequency typically exhibited in highly-branched pol yethylenes. Interestingly, entanglement in the ultra-high molecular weight material impedes crysta llization owing to a slightly reduced Hm

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17 relative to the high-density polymer, but a higher peak melting temperature is observed relative to the high-density polymer indi cating thicker crystalline lamellae. Figure 1-11. Second heating cycle DSC scan s of commercial polyethylene samples at 10oC/min A large majority of polymers and plastics us ed in the world today are produced via ethylene-olefin copolymerization, and as catalyst modification and materials design progress, an ever increasing number of copolymer archit ectures are being developed allowing a more widespread application of commodity materials. As more practical, functional group tolerant homogenous polymer ization catalysts are developed, the copolymerization of ethylene and pola r vinyl monomers produ ces functionalized materials, thereby enabling st ructural modification through th e control of the comonomer feed ratio, the reactivity ratio of the two m onomers in use, and/or the degree of chain transfer during the polymerization. Indus trially, these commerc ial copolymerization

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18 processes are ubiquitous allowi ng the large-scale s ynthesis of ever increasing volumes of various ethylene-based copolymers each year. Ethylene-acrylic acid (EAA) and ethylen e-methacrylic acid (EMAA) copolymers have been prepared in a wide variety of comonomer compositions being applied to numerous applications as the free acid polymers, and, upon neutralization to their respective ionic forms, more chemically a nd physically demanding a pplications such as car bumpers, golf balls, and protective coat ings for reactive chemical storage. Commercial ethylene-based ionom ers create their own class of commodity materials due to the bulk properties and mor phologies only available in thes e systems. The neutralized ionomeric forms of EAA and EMAA copolymer s have significantly improved the impact resistance producing extremely tough thermopl astics due to the well-known three-phase morphology described by Eisenberg92 and studied by many others.93-103 Although early debate in the field did little to reconcile differences in proposed ionomer morphologies, recent high-level secondary structure analysis94, 97, 100-105 along with continued infrared absorbance measurements and thermal analys is have proven the existence of all three phases in EisenbergÂ’s proposal including clusters or multiplets of carboxylate-metal ionic aggregates, crystalline lamellae from the ethylene backbone, and the remaining amorphous material surrounding the aggregates and crystallites. A ll commercial ionomer produced currently rely on a melt-neutraliza tion of acid copolymers with zinc salts usually performed in a twin screw extruder. While this type of synthetic method is amenable to the production of functional ionom ers, the mechanical incorporation of the zinc cations into the polymer matrix does not necessarily guarantee chemical reaction between the protonated carboxylic acid and the zinc salt. Unfortunately, little agreement

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19 has been reached concerning the post-neutralizat ion analysis of ionomers as related to metal and free acid concentrati ons in the final product. Figure 1-12 displays the sec ond heating and cooling scans for a family of Nucrel™ and Surlyn™ materials. For th e Nucrel copolymers, as the aci d content is increased from 11 wt. % to 19 wt. % methacrylic acid, an e xpected reduction in both peak melting value from 94oC to 87oC and heat of fusion from 85 J/g to 92 J/g. Figure 1-12. Second heating cycle DSC scan of commercial carboxylic acid copolymers (Nucrel™) and ionomers (Surlyn™) at 10oC/min For the neutralized ionomers, you can clearl y see the retention of semicrystallinity for all materials regardless of neutralization level, with little change in peak melting or heat of fusion values. The clustering and segr egation of ionic domains into dense clusters has little effect on the crystallization and chin folding for the extended ethylene run lengths in the material.

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20 While proprietary commercial methods a llow the production of various copolymer architectures relevant to an ever increasi ng number of end-use applications by materials modification, ultimate structure control is difficult to obtain applying chain copolymerization methodology. For pr oper examination of fundamental structure-property relationships and determination of key factors related to ultimate bulk copolymer morphology, the creation of model ma terials with utmost control of polymer microstructure is required, and the recent application of olefin metathesis to these synthetic challenges are reviewed in the next section. Although ma ny synthetic strategies have been used to prepare similar copolymers, metathesis polymerizat ions not only offers facile synthesis of model copolymers but al so the ability to control functional group placement and molecular weight while ma intaining ultimate control over polymer branching, the major influencing factors of polymer crystallizati on and bulk morphology. Sequenced Polyolefins via ADMET The thermal analysis data from many sequenced ethylene copolymers prepared via ADMET has been discussed in indivi dual reports and review articles6, 7 detailing trends among the specific families of equivalently func tionalized materials. Brief discussion is included within some experimental detail s and discussion, and one specific report comparing the thermal response of ADMET polyethylene copolymers with pendant functionality on every 18th carbon with a trend of decrea sing melting point and heat of fusion with increase in relative van der Waals radius of the pendant group on the polymer.68 Conclusive delineation of factors controlling crystallization and lamellar thickness for these materials are difficult to determine from a single data set from one sequence length, and only the direct compar ison of a variety of functional groups over

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21 multiple run lengths would allow analysis of the broad scope of material properties and polymer morphologies accessible ap plying this synthetic methodology. Figures 1-13, 1-14, and 1-15 illustrate the thermal responses for a wide variety of ADMET materials synthesized over a decade of research with contributions from 7 individual Wagener group member s, and Table 1-1 displays th ermal data compiled for all materials discussed in this section. Material s with pendant functiona lity every 9, 15, and 21 carbons in the polymer backbone, includ ing seven novel copolymers reported in Chapters 2 and 5 of this dissertation, were selected for presentation as they allow the comparison of thermal responses over a range of functionality and branch frequency. All copolymers were analyzed under identical expe rimental conditions at a scan rate of 10oC/min with second heating curves displayed. Table 1-1. Thermal characterization da ta for sequenced ethylene copolymers Pendant Branch Frequency in Copolymer (x value in monomer) Monomer Structure R2 R1 x x 9 (3) 15 (6) 21 (9) R1 R2 Tg Tm HmTg Tm Hm Tg Tm Hm CH3 H -60-1238 -4339 82 -43 63 117 CH2CH3 H -76u u u -38, -432 u 16 53 n C4H9 H ns ns u 16 54 n C6H13 H -78 -48u u u 16 53 OCH3 H ns u -9 60 u 40 70 OCH2CH3 H ns u -22 36 u 29 74 C(O)OH H 22 u u -4 u u u 45 37 C(O)OH CH3 ns ns u 13 15 C(O)OCH3 CH3 ns ns u 7 45 CH2[OCH2CH2]4OH H -69u u ns u 29 32 CH3 CH3 -48u u -3932 40 u 45 46 * ns = not synthesized, u = unde tected; all reporte d values of Tm in C and Hm in J/g.

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22 The thermal response of six c opolymers functionalized every 9th carbon is shown in Figure 1-13. The morphological effects of regular functiona lization along the polyethylene backbone is apparent as the steric congestion of pendant branches, regardless of functional group identity, renders the materi al amorphous in all but one material in this set of copolymers. Glass tr ansition temperatures for the majority of the materials fell within -80 to -40ºC, typical for polyethylene, disp laying little dependence on functional group size. One unique material is the acid functiona lized copolymer that displays a significantly highe r glass transition temperatur e attributed to extensive hydrogen bonding that will be detailed in Chapter 2. Figure 1-13. Melting profiles of satura ted ADMET polymers with a 9 carbon branch frequency The only semicrystalline copolymer at this branch frequency includes a precisely placed methyl functionality every 9th carbon exhibiting a shar p melting profile, highly

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23 unusual for EP copolymers with this level of propylen e incorporation.106, 107 Interestingly, what appears to be an initial relaxation near -60ºC correlates with similar glass transition temperatures exhibited by th e majority of materials in Figure 1-13 but also suggests greater flexibility of lamellar bound polymer chains in the methyl branched polymer relative to the amorphous acid functio nalized analog exhibi ting stiffer polymers chains attributed to hydrogen bonding. Figure 1-14 displays the thermal profile s for sequenced materials containing a branch point every 15th carbon along the polymer backbone , effectively decreasing the molar concentration of pendant branches re lative to the materials in Figure 1-14. Increasing the ethylene sequence length to 14 me thylene units promotes crystallization in this series of polymers where more than half exhibit some type of melting event upon heating. Once again, the methyl branched polymer is the highest melting material 39 ºC and Hm=82 J/g, while the gem -dimethyl branched material melts only 7ºC lower but exhibits a 50% reduction in Hm. The next two curves a ssociated with a methoxy and ethoxy branched polymers displa y the common trend of incr easing pendant group size to reduction in melting point and heat of melting. Interestingly, alkyl branched materials all tend to display ill-defined melting or multiple relaxations at this run length, and even though ethyl branch size is similar to th e methoxy group, thermal profiles are much different suggesting small dipole-dipole intera ctions promote crystallization in sequenced materials at exact branch frequencies. Simila r to the relationship in Figure 1-13, the acid branched copolymer in Figure 1-14 displays a glass transition te mperature well above other observable relaxations for c opolymers at this run length.

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24 Figure 1-14. Melting profiles of satura ted ADMET polymers with a 15 carbon branch frequency Figure 1-15 displays the thermal profiles fo r copolymers precisely functionalized at every 21st carbon along the polymer backbone. The broad range of melting profiles observed for these family materials is indi cative of the various polymer morphologies available by simple “R group” modification or by the select ion of various run lengths between pendant functionality. Thermal data for the entire series of copolymers for all thermal profiles plotted is included in Tabl e 1-1. While in-depth discussion concerning thermal transitions is omitted as it has been previously presented and is available in the literature, a few interesting comparisons dist illed from the plethora of information that can be derived from Figure 115 are explored. For example, the comment concerning polarity effects on polymer crystallization in the previous secti on can be expanded upon where the same relationship is observed fo r methoxy and ethyl branched materials for this run length. Again, a bimodal response fr om the ethyl branched material occurs at a

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25 lower temperature and Hm than the methoxy polymer, but here the ethoxy polymer melts at a slightly higher temperatur e and double the heat of fusion. Considering the small size differences of methoxy, et hoxy and ethyl branched polymers, it seems pendant group polarity is significantly affecting crystal lite formation. Oddly, the hydrogen bonding hydroxyl terminated tetraethylene (TEG) glycol grafted polyethylene has similar values as the ethoxy material as listed in Table 11, but further experiments are required to determine the phase morphology of such regularly grafted materials. One final note concerning Figure 1-15 is the drastic effect of hydrogen bonding on polymer morphology throughout this series of mate rials already mentioned for the TEG grafted polymer and previous acids models, but also the compar ison of acrylic acid and methacrylic acid functionalized materials. Detailed discu ssion concerning hydrogen bonding in sequenced materials will continue in Chapter 2. Figure 1-15. Melting profiles of satura ted ADMET polymers with a 21 carbon branch frequency

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26 Novel polymers with branch frequencies of 9, 15, 21 carbons reported in this dissertation were included on the data ove rlays above allowing insight into polymer morphology by the juxtaposition of a more de tailed comparative data set. These relationships will be alluded to in individual sections concerning the thermal analysis of each individual family of copolymers. Statistically Random Polyolefins via ROMP Copolymerization The intermediate thermal response of ethylene copolymers created by ROMP methodology relative to that of commercially available or ADMET ma terials directly relates to the polydispersity of ethylen e sequence lengths and lamellar thickness distributions to the broad melting transitions observed with thermal analysis. In most cases, ROMP materials with small percentage s of polar monomer exhibit melting profiles very similar to those of industrially prepar ed copolymers due to similarity of bulk polymer morphology. Although sequence length is variable among ROMP copolymers, the exclusion of short run le ngths in the material yields highly crystalline copolymers with more well-defined melting profiles re lative to commercial polyethylene also influenced by the strictly linear nature of ROMP materials ex hibiting no branching defects seen in many commercial materials. The preparation of copolymers applyi ng ROMP copolymerization of various cyclooctenes has been performed, while only limited data is reported concerning melting point trends with respect to comonomer ratio has been reported. Experiments involving the synthesis of ethylene-vinyl chloride (EVC) copolymers ha ve been reported including in-depth structural and thermal analysis for this novel set of materials87, 88 revealing the dependence of peak melting temperature and prof ile to vinyl chloride concentration in the

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27 copolymer. Similar results were observed upon analysis of EAA, EMAA, ethylene-vinyl alcohol, and ethylene-vinyl acetate materials reporte d previously by our group.86, 108 Purpose of this Dissertation The following text describes the on going investigation into the application of olefin metathesis, mainly ADMET polymeriza tion, to produce ethyl ene copolymers with specific structural features a nd single pendant branch identities. The research presented in this dissertation is significant to the deve lopment of structure-prop erty relationships for widely applied commodity polyolefin material s as well as the crea tion of highly ordered macromolecular structures displaying unique material properties through novel synthetic methods. Chapter 2 describes the synthesis of a family of EAA copolymers where the interaction of ethylene sequence length, polymer crystallinity , and hydrogen bonding is explored in strictly linear sy stems. Chapter 3 describes the preparation of the first sequenced ionomers by the neutralization of previously described sequenced EAA materials also including preliminary char acterization data. Ch apter 4 involves the preparation and characterizati on of a family of ethylenealkyl vinyl ether copolymers unattainable without th e application of olefin metath esis, and the final Chapter 5 describes the polymerization of symmetrical alkyl branched monome rs to produce methyl branched polyolefins with short run lengths of four or six methylene units. As a collective tale, the research described in this document describes the development of synthetic methodology for the preparation of numerous ethylene-based materials with absolute control over pendant group identity and copolymer structure paving the road for the future synthesis of more hi ghly functionalized materials.

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28 CHAPTER 2 LINEAR ETHYLENE-ACRYLIC ACID COPOLYMERS VIA METATHESIS POLYMERIZATION Introduction Chain copolymerized ethylene-acrylic acid (EAA) and ethylene-methacrylic acid (EMAA) copolymers have been widely used as commodity plasti cs due the ease of production, inexpensive starting materials, and the tunable bulk morphology of final products.109 The interplay of hydrogen bondi ng and polymer crystallinity110 permits the synthesis of wide variety of materials displaying various bulk properties dependant on acid content and degree of bran ching. Commercial EAA c opolymer synthesis, usually performed by a radically initia ted, high pressure polymerizat ion, allows the preparation of statistically functionalized copolymers w ith desired material properties; however, both chain transfer side reactions causing uncont rollable polymer branch ing and also random incorporation of acid functiona lity during the polymerization lead to ill-defined polymer microstructures as described previously in Figure 1-11 and revisited in Figure 2-1. Metathesis polymerization has been previous ly applied to the s ynthesis of EAA and EMAA chain copolymer analogs, and recent reports detail the ADMET polymerization of free acid dienes 7, 73 and ROMP copolymerization of cyc lic acid dienes with cyclooctene as illustrated in Figure 2-1.7 Although varying degrees of success have been achieved due to suspected reaction of carboxylic ac id with the catalyst, the successful incorporation of low molar co ncentrations of acrylic acid in ethylene copolymers has been reported.108 Therein, the successf ul preparation of copolymers between 2-10 mol%

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29 was achieved by the copolymerization and subsequent hydrogenation of an acid functionalized cyclooctene as discussed in th e Chapter 1 and descri bed in Figure 2-1. These materials were isolated as high-me lting, semicrystalline solids, as expected, affording strictly linear materials exhibiting varying levels of crys tallinity dependant on comonomer incorporation,7 typical of commercially produced EAA and EMAA copolymers. Acyclic Diene Metathesis Linear Polymer, Precisely Placed Acid Group Ring Opening Metathesis Polymerization Linear Polymer, Randomly Placed Acid Group Catalyst xy n OH O H2CCH2 H2C CH HO O OH xx O OH x x O n H2CCH2 Catalyst R Hydrogenation O OH y n 3 2 6 x y Hydrogenation 8 4 3 n xy O OH O OH O HO Free Radical Polymerization Branched Polymer, Randomly Placed Acid Group Figure 2-1. Three modes of EAA copolym er synthesis and alternative copolymer structures Presented in this chapte r is a systematic study of EAA copolymer structureproperty interactions within st rictly linear macromolecules through the application of two modes of olefin metathesis polymerization. Approaching EAA synthesis in this manner allows the production of both precisely f unctionalized copolymers with a defined ethylene sequence length between pendant carboxylic acid groups as well as statistically functionalized copolymers with a random pl acement of pendant acid groups and a distribution of ethylene sequence lengths. Metathesis polymerization products were

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30 subsequently hydrogenated generating fully saturated EAA copolymers allowing direct comparison of ethylene sequence length dist ributions in materials with comparable comonomer ratios to determine the effects of controlled branch fr equency on structural and thermal analysis, especially melting behavior. Described herein is the total synthesis and characterization of seven examples of linear EAA copolymers applying the well-known ADMET and ROMP polymerization-hydrogenation methodology. Experimental Section Materials All chemicals were purchased from Aldric h and used as received unless otherwise specified. Cyclooctene was dried over CaH2 and freshly distilled prior to use. First generation GrubbsÂ’ catalyst was a gift from Materia, Inc. and was used as received. Preparation of was performed as previous ly reported 2-(4-cyclooctenyl)acetic acid,108 as well as 2-(4-pentenyl)-6-hepteneoic acid, 2 -(7-octenyl)-9-deceneoic acid, and 2-(10undecenyl)-12-trideceneoic acid.62 Instrumentation and Analysis All 1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were recorded on a Varian Associates Mercury 300 spec trometer. Chemical shifts for 1H and 13C NMR were referenced to residual signals from d8 -dioxane (1H = 3.53 ppm and 13C = 39.50 ppm), d6 THF (1H = 3.58 ppm and 13C = 25.4 ppm), or CDCl3 (1H = 7.27 ppm and 13C = 77.23 ppm) with 0.03% v/v TMS as an internal refe rence as listed. Thin layer chromatography (TLC) was performed on EMD silica gel coated (250 m thickness) glass plates. Developed TLC plates were st ained with iodine absorbed on silica to produce a visible signature. Reaction conversions and relative purity of crude products were monitored by

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31 TLC chromatography and 1H NMR. Fourier transform in frared (FT-IR) measurements were conducted on polymer films cast from chloroform onto KBr plates using a Bruker Vector 22 Infrared Spectrophotometer. Differential scanning calorimetry (DSC) wa s performed using a Thermal Analysis (TA) Q1000 at a heating rate of 10ºC/min under nitrogen purge . Calibrations were made using indium and freshly distilled n -octane as the standards for peak temperature transitions and indium for the enthalpy st andard. All samples were prepared in hermetically sealed pans (4-7 mg/sample) and were run using an empty pan as a reference. Thermogravimetric analysis (TGA) was performed on a TA Q500 using the dynamic high-resolution analysis mode. Gel permeation chromatography (GPC) was performed using a Waters Associates GPCV2000 liquid chromatography system with its internal differen tial refractive index detector (DRI) at 40C using two Waters Styragel HR -5E columns (10 microns PD, 7.8 mm ID, 300 mm length) with HPLC grade THF as the mobile phase at a flow rate of 1.0 mL/minute. Injections were made at 0. 05-0.07 % w/v sample concentration using a 220.5 l injection volume. Retention times were calibrated against narrow molecular weight polystyrene standards (P olymer Laboratories; Amherst, MA). All standards were selected to produce Mp or Mw values well beyond the expected polymer's range. Monomer Synthesis A general procedure for acid protection A solution of 2-(4-pentenyl)-6-hepteneoic ac id (1 eq.) in diethyl ether (20 mL) was slowly added via Pasteur pipette to a precooled (0C) solution of ethyl vinyl ether (excess, usually >4 eq.) and phosphoric acid (cat., 1 drop from capillary pipette) in

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32 diethyl ether (10 mL). The solution wa s stirred cold for 30 minutes under argon, and then warmed to room temperature for 3 days. Basic alumina (~1g) was added to the reaction mixture and stirred for five minutes . After filtration and solvent removal, 1 was isolated as 7.3 g (99.0% yiel d) of colorless oil with no further purification required. O O 33 O 1-ethoxyethyl-2-(pent-4-enyl)hept-6-enoate (2-1) 98.2 % yield. 1H NMR (CDCl3): (ppm) 1.22 (t, 3H) 1.30-1.55 (br, 9H), 1.62 (m, 2H), 2.05 (q, 4H), 2.36 (m, 1H), 3.53 (d, 1H ), 3.71 (m, 1H), 4.97 (m, 4H), 5.82 (m, 2H), 5.94 (q, 1H); 13C NMR (CDCl3): (ppm) 15.24, 21.14, 26.86, 26.89, 31.91, 32.10, 33.76, 45.98, 64.77, 96.33, 114.92, 138.56, 176.17; O O 66 O 1-ethoxyethyl-2-(oct-7-enyl)dec-9-enoate (2-2) 99.1 % yield. 1H NMR (CDCl3): (ppm) 1.16-1.53 (br, 24H), 1.61 (m, 2H), 2.04 (q, 4H), 2.34 (m, 1H), 3.53 (m, 1H), 3.71 (m , 1H), 4.97 (m, 4H), 5.81 (m, 2H), 5.95 (q, 1H); 13C NMR (CDCl3): (ppm) 15.24, 21.13, 27.59, 27.65, 29.03, 29.15, 29.58, 32.52, 32.71, 33.94, 46.30, 64.72, 96.22, 114.41, 139.27, 176.42; O O 99 O 1-ethoxyethyl-2-(undec-10-en yl)tridec-12-en oate (2-3) 98.4 % yield. 1H NMR (CDCl3): (ppm) 1.16-1.53 (br, 36H), 1.60 (m, 2H), 2.04 (q, 4H), 2.33 (m, 1H), 3.54 (m, 1H), 3.71 (m , 1H), 4.97 (m, 4H), 5.81 (m, 2H), 5.95 (q,

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33 1H); 13C NMR (CDCl3): (ppm) 15.24, 21.13, 27.59, 27.65, 29.03, 29.15, 29.58, 32.52, 32.71, 33.94, 46.30, 64.72, 96.22, 114.41, 139.27, 176.42; O O O 1-ethoxyethyl-2-(cyclo-4-octenyl)acetate (2-4) Prepared from 2-(4-cyclooctenyl)acetic acid. 1H NMR (CDCl3): (ppm) 1.19 (t, 3H), 1.40 (d, 3H), 1.51-1.79 (br, 3H),1.98-2.25 (br, 4H), 2.38 (m, 1H), 2.47 (m, 1H), 3.52 (m, 1H), 3.69 (m, 1H), 5.66 (m, 2H), 5.92 (q, 1H); 13C NMR (CDCl3): (ppm) 15.26, 21.02, 24.32, 26.08, 26.11, 28.02, 29.51, 29.63, 31.77, 31.91, 43.86, 64.72, 64.78, 96.18, 129.71, 129.75, 130.74, 130.81, 177.55, 177.57; General procedure for free and acid protected ADMET polymerization 2-(4-pentenyl)-6-hepteneoi c acid (1g) was added to a 50mL round bottomed flask equipped with a magnetic stir bar and dega ssed by stirring under high vacuum for one hour. Grubbs first generation catalyst (400:1 m onomer:catalyst) was added to the flask, and high vacuum (10-4 torr) was applied slowly over one hour then, the temperature was raised to 50oC for 72 hours. Upon cooling the room temperature, ethyl vinyl ether (~10 drops) in toluene (50 mL) was added to th e polymerization flask and stirred until all solids dissolved. Precipitation of the crude so lution into slightly acidic (1M HCl) MeOH (500 mL) and subsequent filtration followe d by vacuum drying afforded 987 mg of unsaturated polymer as brown tacky solid.

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34 3 3 n O OH Polymerization of 2-(4-pentenyl)-6-hepteneoic acid (2-5) 1H NMR (300 MHz, CDCl3): 5.8 (m, 1H) 5.38 (m, 40.03H); 5.05 (m, 1.99H) 2.40 (m, 41.2H), 2.06 (m, 81.43H), 1.7-1.2 (m, 170.54H); IR (, cm-1): 2920, 2850, 1702, 1649, 966. 3 3 n O O O Polymerization of 2-1 (2-6) 1H NMR (CDCl3): (ppm) 1.16-1.51 (br, 12H), 1.60 (m, 2H), 1.97 (q, 4H), 2.33(m, 1H), 3.53 (m, 1H), 3.70 (m, 1H ), 5.35 (m, 2H), 5.94 (q, 1H); 13C NMR (CDCl3): (ppm) 15.27, 21.15, 27.31, 27.62, 32.09, 32.29, 32.65, 46.06, 64.73, 96.26, 129.83, 130.32, 176.21; FT-IR: (cm-1) 2978, 2926, 2854, 1733, 1704, 1464, 1376, 1124, 1039, 948, 965, 849, 723. 6 6 n O O O Polymerization of 2-2 (2-7) 1H NMR (CDCl3): (ppm) 1.16-1.51 (br, 24H), 1.60 (m, 2H), 1.95 (q, 4H), 2.32 (m, 1H), 3.53 (m, 1H), 3.71 (m, 1H), 5.35 (m, 2H), 5.95 (q, 1H); 13C NMR (CDCl3): (ppm) 15.25, 21.14, 27.41, 27.66, 27.72, 29.27, 29.40, 29.64, 29.79, 29.91, 32.60, 32.79, 46.36, 64.72, 96.20, 130.02, 130.49, 176.46; FT-IR: (cm-1) 2977, 2926, 2852, 1732, 1704, 1463, 1376, 1124, 1037, 948, 965, 852, 721.

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35 9 9 n O O O Polymerization of 2-3 (2-8) 1H NMR (CDCl3): (ppm) 1.30-1.51 (br, 36H), 1.60 (m, 2H), 1.96 (q, 4H), 2.32 (m, 1H), 3.53 (m, 1H), 3.71 (m, 1H), 5.38 (m, 2H), 5.95 (q, 1H); 13C NMR (CDCl3): (ppm) 15.26, 21.15, 27.45, 27.70, 27.75, 29.42, 29.55, 29.90, 30.00, 32.84, 46.37, 64.71, 96.19, 130.02, 130.08, 130.54, 176.46; FT-IR: (cm-1) 2978, 2925, 2854, 1732, 1705, 1463, 1378, 1124, 1037, 948, 966, 852, 722. General conditions for Parr bomb hydrogenation A solution of 2-5 (1.0 g, 4.45 mol olefin) was di ssolved in a toluene (100mL) and 1-butanol (50mL) mixture and then dega ssed by bubbling a nitrog en purge through the stirred solution for 30 minutes. So lid WilkinsonÂ’s catalyst (3.7 mg, 4 mol) [RhCl(PPh3)3] was added to the solution, and the gl ass sleeve was sealed in a Parr reactor equipped with a temperature probe, pressure gauge, and a paddle wheel stirrer. The reactor was filled to 400 p.s.i. hydrogen gas a nd purge three times while stirring, filled to 400 psi hydrogen, and heated to 80oC for 48 hours. Upon cooling to room temperature and safely releasing pressure using a vent valve, the crude solution was precipitated into methanol, filtered, and dried affording 994 mg (99% yield) of saturated EAA copolymer. n OH O EAA9 (2-9): Hydrogenation of 2-5 FT-IR (, cm-1): 2920, 2850, 1702, 1461, 721

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36 EAA9 (2-10): Hydrogenation of 2-6 1H NMR (dioxane): (ppm) 1.19-1.65 (br, 16H), 2.24 (m, 1H); 13C NMR (dioxane): (ppm) 28.21, 30.21, 30.27, 30.36, 33.14, 45.93, 177.41; FT-IR (, cm-1): 2921, 2852, 1704, 1461, 1418, 1287, 1235, 931, 721 OH O EAA15 (2-11): Hydrogenation of 2-7 1H NMR (dioxane): (ppm) 1.20-1.65 (br, 28H), 2.24 (m, 1H); 13C NMR (dioxane): (ppm) 28.21, 30.28, 30.38, 30.43, 33.10, 45.89, 177.43; FT-IR (, cm-1): 2921, 2852, 1704, 1461, 1417, 1288, 1234, 930, 721 OH n O EAA21 (2-12): Hydrogenation of 2-8 1H NMR (dioxane): (ppm) 1.07-1.65 (br, 40H), 2.25 (m, 1H); 13C NMR (THF): (ppm) 28.60, 30.69, 30.85, 33.57, 46.32, 177.29; FT-IR (, cm-1): 2920, 2851, 1704, 1461, 1419, 1288, 1235, 933, 723 General conditions for free acid ROMP copolymerization Distilled cyclooctene (1.43 g, 13.0 mmol) was syringed into a 10 mL oven dried vial with a stir bar. 2-(4-cyclooctenyl)acet ic acid (1.78 g, 11.6 mmol) and chloroform (10 mL) was added to the vial and the mixture was stirred for 30 minutes under a stream of nitrogen. GrubbsÂ’ second genera tion catalyst (8.6 mg, 1.01 x 10-2 mmol) in chloroform (0.5 mL) was added via syringe to the vigorous ly stirred vial. After stirring at room temperature until the solution became highly viscous and warm to the touch, the

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37 polymerization mixture was a llowed to stand overnight und er a nitrogen gas. The polymerization was quenched by the addition of ethyl vinyl ether (~10 drops) in chloroform (10 mL) with 2,6-ditert -butyl-4-methylphenol (5 mg ) included as a radical scavenger to prevent crosslinking. Upon isolation of the extremely adhesive polymer from the precipitation, the unsaturated material was only analyzed by GPC due to disappointing molecular weight s attained by free acid ROMP. x y O OH n For 15 mol% EAA (2-13) FT-IR (, cm-1): 2926, 2854, 1705, 1649, 966; 1H NMR (CDCl3): 5.50 (br, 16.43), 2.40 (br, 1H), 2.06 (br, 33.12H), 1.7-1.3 (br, 65.23). For 9 mol% EAA (2-14) FT-IR (, cm-1): 2926, 2855, 1705, 1649, 966; 1H NMR (CDCl3): 5.50 (br, 5.53), 2.40 (br, 1H), 2.06 (br, 11.14H), 1.7-1.3 (br, 20.45). For 3 mol% EAA: (2-15) FT-IR (, cm-1): 2920, 2850, 1705, 1649, 966; 1H NMR (CDCl3): 5.50 (br, 3.27H), 2.40 (br, 1H), 2.06 (br, 6.54H), 1.7-1.3 (br, 11.08 H). Diimide hydrogenation procedure This method was applied for the saturation of only copolymers 2-13 through 2-15 due to solubility issues that were eventu ally overcome. A solution of unsaturated polymer 2-13 (1.0 g, 8.78 mmol olefin) was dissolved in xylenes (30 mL) in a 350 mL three-neck round bottomed flask. Tripropyl amine (3.79 g, 26.3 mmol) was added via syringe followed by addition of p-toluenes ulfonhydrazide (4.33 g, 23.3 mmol) using a

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38 powder funnel. The reaction mixture was heated to 135C for 2 hours with vigorous stirring while monitoring nitrogen production with a mineral oil bubbler. Upon cessation of nitrogen production and cooling to room te mperature, a second batch of equivalent amounts of tripropyl amine and p -toluenesulfonhydrazide were added and the reaction mixture was heated to 135C for 2 hours. Reprecipitation of crude mixtures into acidic (1M HCl) methanol, followed by filtration and subsequent drying afforded the saturated EAA copolymer analog as a 910mg ( 90% yield) of white powder. In some instances, polymers were precip itated a third time to eliminate a strong sulfur odor, and all isolated materials we re insoluble in common organic solvents. x y O OH n 15% Acrylic Acid-Ethylene Copoly mer (2-16): Hydrogenation of 2-13 FT-IR (, cm-1): 2917, 2848, 1700, 1460. 9% Acrylic Acid-Ethylene Copoly mer (2-17): Hydrogenation of 2-14 FT-IR (, cm-1): 2918, 2850, 1701, 1460. 3% Acrylic Acid-Ethylene Copoly mer (2-18): Hydrogenation of 2-15 FT-IR (, cm-1): 2918, 2848, 1700, 1461. General conditions for protected acid ROMP copolymerization Cyclooctene (0.55 g, 5.0 mmol) and 2-1 (9.00 g, 39.7 mmol) were added toluene (30mL) in a 200 mL round bottomed flask unde r nitrogen purge. The reaction mixture was heated to 50oC, and a solution of Grubbs’ first ge neration catalyst (53 mg, 6.4 µmol, 1000:1 monomer:catalyst) in dichloromethane (0.5 mL) was added to the magnetically stirred reaction mixture. Af ter four hours, the polymerizat ion mixture was quenched by

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39 addition of ethyl vinyl ether (~10 drops) and allowed to stir for 5 minutes. Upon precipitation of crude solution into acidic (1M HCl) methanol, the unsaturated polymer product was isolated as a mildly adhesive solid. No furthe r purification of unsaturated prepolymers was necessary. x y O O O n For 22.2 mol% EAA (2-19) 13C NMR (CDCl3): (ppm) 15.27, 21.16, 27.31, 27.61, 32.10, 32.30, 32.66, 46.08, 64.73, 96.26, 129.84, 130.33, 176.21; FT-IR: (cm-1) 2978, 2926, 2854, 1733, 1704, 1464, 1375, 1124, 1039, 949, 966, 849, 723. For 13.3 mol% EAA (2-20) 13C NMR (CDCl3): (ppm) 15.27, 21.16, 27.30, 27.61, 32.10, 32.30, 32.66, 46.10, 64.73, 96.26, 129.85, 130.33, 176.21; FT-IR: (cm-1) 2980, 2926, 2853, 1733, 1704, 1464, 1376, 1122, 1041, 948, 966, 849, 723. For 9.5 mol% EAA (2-21) 13C NMR (CDCl3): (ppm) 15.26, 21.16, 27.31, 27.61, 32.10, 32.30, 32.66, 46.08, 64.73, 96.27, 129.84, 130.33, 176.21; FT-IR: (cm-1) 2978, 2927, 2854, 1733, 1704, 1464, 1375, 1125, 1039, 948, 965, 849, 721. For 4.5 mol% EAA (2-22) 13C NMR (CDCl3): (ppm) 15.27, 21.15, 27.31, 27.61, 32.11, 32.30, 32.66, 46.08, 64.73, 96.25, 129.84, 130.31, 176.21; FT-IR: (cm-1) 2978, 2926, 2855, 1733, 1705, 1464, 1376, 1124, 1039, 948, 965, 849, 722.

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40 Hydrogenation of unsaturated ADMET and ROMP products Parr bomb hydrogenation procedure Same procedure as described previously for ADMET EAA materials but run at temperatures over 100oC to ensure copolymer solubility. x y O OH n ROMP EAA22.2 (2-23): Hydrogenation of 2-19 FT-IR (, cm-1): 2920, 2850, 1704, 1460, 719 ROMP EAA13.3 (2-24): Hydrogenation of 2-20 FT-IR (, cm-1): 2919, 2851, 1705, 1466, 721 ROMP EAA9.5 (2-25): Hydrogenation of 2-21 FT-IR (, cm-1): 2920, 2850, 1704, 1469, 715 ROMP EAA4.5 (2-26): Hydrogenation of 2-22 FT-IR (, cm-1): 2920, 2850, 1705, 1469, 715 Results and Discussion ADMET and ROMP Monomer synthesis Free acid olefins employed in this study were prep ared by reported synthetic procedures,62, 108 producing ADMET monomers on th e 5-10 gram scale and ROMP monomers up to 25 grams in a single reaction.

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41 OH xx O H3PO4, Et2O O xx O O O x = 3, 6, 9 x = 3 ( 2-1 ) 6 ( 2-2 ) 9 ( 2-3 ) H3PO4, Et2O O O OH O O O 2-4 Figure 2-2. Synthesis of prot ected ADMET and ROMP monomers Upon the realization of poor cat alyst performance in the pr esence of carboxylic acids as discussed in the next section, the preparat ion of protected acid m onomers was performed using a unique, thermally labile hemiacetal ester moiety111-113 shown in Figure 2-2. Metathesis Polymerization of Acid Monomers Metathesis polymerization in the presen ce of free acid functionality has been performed in the synthesis of an EMAA c opolymer requiring successive additions of catalyst upon the observation of low molecu lar weight precuts applying standard ADMET techniques.73 Poor monomer conversion and production of low molecular weight materials was overcome by the successive addition of catalyst to the polymerization mixture afford ing desired EMAA copolymer at typical molecular weight for ADMET polymerization. Concurrently, th e synthesis of randomly functionalized, yet linear EAA copolymers containing low concen trations of acid functionality were prepared via ROMP generating hi gh molecular weight materials.86, 108 A combination of these synthetic tec hniques was applied to EAA copolymer synthesis using ADMET and ROMP chemistry with diimide hydrogenation allowing the

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42 comparison of equimolar concentrations of acrylic acid in EAA systems having dissimilar copolymer micros tructures and highly varied ethylene sequence length distributions (Figure 2-1). Un fortunately, the detrimental effect of high concentrations of free acid on catalyst activity in bulk polymer izations is clear as only low molecular weight materials were isol ated applying both ADMET and RO MP techniques (Table 21). Strangely, ROMP copolymerization exhibited an increase in molecular weight with increasing acid content that was unexpected at first, but ratio nalized upon further analysis. As bulk cyclooctene copolyme rization proceeds building up unsaturated copolymers, the increased acid content in the material inhibits polyoctenamer-like crystallization allowing great er catalyst mobility for l onger reaction times affording higher molecular weight polymer. Upon this observation, bulk ROMP copolymerizations were abandoned for more contro llable solution-based techniques. Table 2-1. Molecular weight data for ADMET and ROMP unsaturated free acid copolymers EAA Copolymer Acrylic Acid Content (mol %) Mn (g/mol) PDI 2-5 22.2 2800 1.45 2-13 3.0 4200 1.76 2-14 9.0 5700 1.95 2-15 15.0 9800 1.83 Metathesis Polymerization of Hemi acetal Ester Protected Monomers Facile protection of all acid monomers followed by metathesis polymerizations were performed as detailed in Figure s 2-3 (ADMET) and 2-4 (ROMP). ADMET polymerization of protected dienes proceeded normally with little if any effect from the hemiacetal ester on the reaction as well as solution-based ROMP copolymerizations. Protected, unsaturated polymers were isol ated at typical molecular weights for both methods, and characterization data is comp iled in Table 2-2. The application of

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43 protection chemistry in this synthesis has allowed the bulk polymerization of functionalized materials yiel ding high molecular weight EAA copolymer analogs with controlled comonomer ratios and ethylene sequence length distributions. O xxO O O xxO O n xx nOH O ii y nOH O x = 3 ( 2-1 ) 6 ( 2-2 ) 9 ( 2-3 ) x = 3 ( 2-6 ) 6 ( 2-7 ) 9 ( 2-8 ) y = 8, EAA9 ( 2-10 ) 14, EAA15 ( 2-11 ) 20, EAA21 ( 2-12 ) OH 33O OH 33O n2-5 y=8, EAA9 ( 2-9 ) i i ii Figure 2-3. EAA copolymer synthesis via ADMET. (i) 1st. generation Grubbs catalyst, vacuum; (ii) H2 (600 p.s.i.), RhCl(PPh3)3, toluene, 1-butanol O OH x y O O O x y O OH n 2-16 15 mol% AA 2-17 9 mol% AA 2-18 6 mol% AA 2-19 for 22.2 mol% AA 2-20 for 13.3 mol% AA 2-21 for 9.5 mol% AA 2-22 for 4.5 mol% AA 2-23 22.2 mol% AA 2-24 13.3 mol% AA 2-25 9.5 mol% AA 2-26 4.5 mol% AA x y O OH n 2-13 for 15 mol% AA 2-14 for 9 mol% AA 2-15 for 6 mol% AA O O O 2-4 ii iii i iv Figure 2-4. EAA copolymer synthesis via ROMP. (i) 1st. generation Grubbs catalyst, neat; (ii) TsNHNH2, tripropyl amine, 140oC; (iii) 1st. generation Grubbs catalyst, toluene, 60oC; (iv) H2 (600 p.s.i.), RhCl(PPh3)3, toluene, 1-butanol

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44 Table 2-2. Molecular weight data for protected, unsat urated copolymers GPC data Unsaturated Copolymer (Target EAA Copolymer) Mn Mw PDI 2-6 (EAA9) 25.1 40.8 1.62 2-7 (EAA15) 31.8 59.1 1.86 2-8 (EAA21) 37.7 65.2 1.73 2-19 (ROMP EAA 22.2) 85.0 106.2 1.25 2-20 (ROMP EAA 13.3) 80.5 111.1 1.38 2-21 (ROMP EAA 9.5) 85.4 163.9 1.41 2-22 (ROMP EVE 4.5) 93.6 128.2 1.37 Hydrogenation of Metathesis Products to Saturated EAA Copolymers Two methods of hydrogenation were applied to fully saturate metathesis products including standard Parr techni ques and a slightly different approach applying a diimide reduction. Free acid copolymers, originally deemed insoluble, were reduced by the aforementioned diimide reduction due to allo w observation of the EAA copolymer using standard lab glassware rather than a steel Parr reactor. The preferred method of hydrogenating polymer s is the use of WilkinsonÂ’s catalyst under an atmosphere of hydrogen gas in a Parr Bomb. This highly efficient reaction can be run at any temperature with any solvent due to the sealed reactor. Here, the use of a binary solvent mixture of toluene and 1-but anol offers good solubility for the fairly nonpolar protected polymer, but also solvates the deprotected and fully saturated EAA copolymer ensuring complete conversion of ol efin and deprotection. As a side note, reaction times were greatly reduced using roughly 15 volume percent of a small alcohol (1-butanol or isopropanol) mixed in toluene. Characterization data is noted for fully satura ted materials, but the limited solubility of these materials precludes them from many form s of analysis including NMR or GPC. In

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45 this case, values from the protected polymer s were used as molecular weight data for saturated materials as previous studies have shown no degradation during either hydrogenation. Even for very soluble pol ymers like the sequenced ADMET copolymer, hydrogen-bonding induced aggregation duri ng the GPC experiment over estimates molecular weight data sometimes up to two orders of magnitude. Table 2-3. Characterization da ta for sequenced EAA materials Comonomer (mol%)a GPC data Saturated EAA Copolymer Ethylene Acrylic Acid Mn Mw PDI EAA9 (2-10) 77.8 22.2 25.1 40.8 1.62 EAA15 (2-11) 86.7 13.3 31.8 59.1 1.86 EAA21 (2-12)) 90.5 9.5 37.7 65.2 1.73 ROMP EAA 22.2 (2-23) 77.8 22.2 85.0 106.2 1.25 ROMP EAA 13.3 (2-24) 86.7 13.3 80.5 111.1 1.38 ROMP EAA 9.5 (2-25) 90.5 9.5 85.4 163.9 1.41 ROMP EAA 4.5(2-26) 95.5 4.5 93.6 128.2 1.37 a) calculated from expected pol ymer repeat unit and confirmed by 1H NMR. Structural Analysis of EAA Copolymers 13C and 1H NMR Primary structural analys is of copolymer architect ures was performed by both 1H and 13C NMR throughout the synthesis of these materials monitoring reaction conversion and preparation of intermediates. While the application of both techniques is helpful in characterization and purity analysis, 13C NMR has proven the most valuable tool for structural analysis in polyet hylene-based materials due to the ability to resolve minor differences in C-C and C-H bonding arrangem ents indistinguishable by most other analytical methods, including 1H NMR.

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46 In-depth structural analysis appl ying carbon NMR reveals the pristine microstructure of ADMET materials by the lim ited number of signals in the alkyl region upon EAA synthesis. Figure 2-5 displays the evolution of 13C spectral data throughout the polymerization and h ydrogenation starting from 2-8 and ultimately affording EAA21 upon completion of the reaction sequence. The protected monomer exhibits many signa ls corresponding to the various alkyl moieties in the material, but downfield signals associated with the protected ester and the terminal olefin are important features to track during the co nversion of monomer 2-8 to EAA21 . Upon polymerization to the unsaturated copolymer, the appearance of a two signals near 130 ppm associated with a 1,2-di substituted olefin, and the lack of remaining terminal olefin signals, indicat es successful polymerization to high molecular weight. All signals corresponding to the pr otecting group remain in t act indicating successful protection of the acid functiona lity, and illustrate the co mpatibility of ruthenium catalysis with this seldomly used protecti ng group, even though is it constructed from ethyl vinyl ether, a common quenching ag ent for metathesis reactions. After hydrogenation of the unsaturated, pr otected polymer, spectral data for the target copolymer EAA21 is simplified to only 5 unique si gnals. Branch point (B) and carbonyl carbon (A) can be observed as th e furthest downfield signals in EAA21 due to the loss of both signals near 130 ppm corre sponding to the olefin , thereby indicating successful saturation of the copolymer. Also, the absence of signals at 96.2 and 64.7 ppm indicate the quantitative deprotection of th e hemiacetal ester back to the corresponding acid in this two-step, one pot reaction also yielding ethyl ether as a byproduct.

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47 Figure 2.5. 13C NMR tracking the conversion of the protected monomer to unsaturated copolymer to saturated, free acid copolymer EAA21

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48 Scanning toward the aliphatic region of the spectrum for EAA21 , the standard large resonance at 30 ppm is observed correspondi ng to the high molar concentration of methylene units throughout the polymer backbone. This signal is flanked on both sides by resonances at 28.6 and 30.85 ppm, corres ponding to carbons D and C, respectively, and strikingly similar to spectral data for previously reported ADMET materials.114 The simplification of carbon NMR data and isolation of specific chemical shift data for exact branching patterns in EAA copolymers has b een achieved applying metathesis techniques to EAA copolymer synthesis. Although ROMP copolymer synthesis can be monitored in a similar fashion, the insolubility of the highly crystalline target ROMP EAA materials prevents solution based analys is like NMR. While the development of monomer and unsaturated polymer structure can be monitored during each synthetic conversion, FT-IR is better suited for the ultimate structur al analysis of these EAA materials. FT-IR Analysis FT-IR analysis of final EAA product copolymers was performed allowing the delineation of many important st ructural details concerning carboxylic acid dimerization and polyethylene-like crystallization. This technique was also employed to monitor the deprotection of the acid during th e hydrogenation reaction. Figure 2-6 illustrates the conversion of protected, unsat urated polymer 2-8 to the target copolymer EAA21 . In this example, the ADMET product exhibits very strong absorbance bands at 2925, 2854, 1461, and 722 cm-1 associated with the methylene vibrations along the entire polymer backbone. Numerous bands in the fingerprint region of the spectrum along with a ve ry strong absorbance at 1732 cm-1 indicate the presence of the hemiacetal ester, although it is evident by the band at 1705 cm-1, associated with

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49 dimerized carboxylic acids, that this polymer was partially deprotected at some point either during the polymerization or workup. A single olefinic absorbance can be observed at 966cm-1 indicating the presence of the 1,2disustituted olefins distributed throughout the polymer backbone, also an indication of successful metathesis polymerization. Hydrogenation and deprotection of polymer 2-8 yields sequenced copolymer EAA21 evident by the loss of olefinic signal as well as those associated with the protecting group . Similar to 13C NMR data presented in th e previous section, the removal of the hemiacetal functional group lead s to great simplification in absorbance data, especially in the fingerprint region of the spectrum where multiple absorbances were witnessed for all protected materials. 60 65 70 75 80 85 90 95 100 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 O n O O OH O a) b) Wavenumber (1/cm)Absorbance Figure 2-6. FT-IR analysis of hydrogena tion-deprotection reacti on from unsaturated polymer 2-8 to copolymer EAA21 ( 2-12 )

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50 The presence of a single absorbance at 1705cm-1 not only confirms quantitative deprotection but also indicates the preval ent dimerization of carboxylic acid groups throughout the material, w ith no free acids (1750 cm-1) observed for any EAA copolymers in this study. The propensity for carboxylic acids to self -associate in this manner creates dynamic physical crosslinks in EAA materials regardless of acid content or sequence length distribution. This f eature of EAA copolymer morphology is not unique to ADMET materials, where it is commonly observed in commercial EAA copolymers as one of the strongest associ ative forces in any ethylene copolymers allowing materials like Nucrel to be applied as commodity plastics to a wide range of applications. Preliminary Small-Angle X-ray Scattering Secondary structure analysis of EAA materials has been performed applying SAXS as a way to probe molecular-level order allowi ng determination of structural parameters from particle size to lamellar spacing for semicr ystalline materials. In this manifestation, we have applied SAXS analysis to probe secondary structure in EAA21, the only example of sequenced EAA copolymers exhibiti ng semicrystallinity tht will be discussed in the thermal analysis section of this chapter. Figure 2-7 illustrates two samples of E AA21 as analyzed by SAXS displaying the respective scattering patterns for a melt -pressed sample and a drawn sample EAA21 . The melt-pressed copolymer exhibits a broad amorphous halo a small length scales indicating a mostly disordered structure throughout the sample. The small ring towards the center of the melt-pressed sample is unique to sequenced ADMET materials and has never been seen in any EAA copolymers to date. Scattering at this angle corresponds

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51 roughly to 2.7 nm, the spacing of acid moieties along the copolymer backbone. Interestingly, this data suggests orderi ng of the acid units even though the broad amorphous halo attributed to disordered polyethylene ch ains suggests otherwise. Figure 2-7. SAXS analysis of melt pressed and drawn EAA21 A drawn sample of the same material was analyzed in a similar fashion to try and expand on the knowledge gained from SAXS an alysis. Here, the drawing of the bulk material forces added orientation into the pol ymer matrix by the slow disentanglement of polymer chains and ordering along the draw axis, which is in the vertic al direction in the Figure2-7. The shift of the amorphous contri bution into an ellipti cal scattering pattern indicates a low degree of crystalline orde r in the material as amorphous scattering perpendicular to the orientati on axis prevails. Also ordere d perpendicularly to the draw axis are the low angle reflections associat ed with the inter-acid distance along the polymer backbone. The ordering of these refl ections can only suggest inclusion of these acids groups into the crystalline lamellae, but FT-IR analysis indicated acid dimers meaning the entire dimerized carboxylic acid must be included in the crystal! While

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52 these preliminary results suggest unique struct ures of highly disordered polymer crystals, thermal analysis is applied to these material s in the following section to further unravel the mystery of sequenced EAA morphology. Thermal Analysis of Linear EAA copolymers Differential scanning calorimetry (DSC ) was performed on vacuum dried EAA copolymers to ensure complete removal of solv ent prior to analysis. Thermal profiles for ADMET and ROMP materials are presented in Figures 2-8 and 2-9, respectively, indicating the drastic effects of sequen ce length distribution on bulk copolymer morphology. DSC analysis for EAA copolymers produ ced by ADMET is typical for most sequenced materials, where decreasing th e pendant branch frequency yields less crystalline materials to some point where completely amorphous copolymers are isolated due to increased steric congestion and a lack of polymer nucleation. For the EAA series, only EAA21 displays melting behavior as indicated by a large endothermic transition at 45oC exhibiting a heat of fu sion of 37 J/g, while EAA9 and EAA15 display fully amorphous character exhibiting clearly visible glass tran sition temperatures at 22oC and 4oC, respectively. The fact that EAA9 is a more rigid polymer is intuitive as the higher molar concentration of dimerized acid groups leads to extremely stiff polymer chains relative to EAA15 . The boundary of amorphous and semi crystalline copolymers in this family of sequenced materials resides at a longer branch frequency than most ADMET copolymers series indicating the detrim ental effects of hydrogen bonding on polymer crystallization.

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53 Figure 2-8. DSC overlay for ADMET EAA copolymers Analysis of ROMP materials follows more closely to that of industrial materials present in Chapter 1 where a consistent incr ease in peak melting temperature and heat of fusion is linked with a decrease in acid content. Although the limited sequence lengths created during ROMP polymeri zation seem to have little effect on polymer morphology up to 13.3 mol% acrylic acid, the 22.2 mol% acrylic acid copolymer is completely amorphous on first and second scans where simila r industrial material still maintain their semicrystallinity at this level of func tionalization due to the presence of long, uninterrupted ethylene sequences and closely associated acid un its in the polymer chain. This phenomena, as associated with the mini mum run length distributions for cyclooctene copolymerization mentioned in Chapter 1, indi cates that regular spacing of pendant acid unit could be considered a way to maximizing the effect of the defect branch across the

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54 majority of the polymer chain allowing no i ndividual segment to nucleate. The presence of acid dimers throughout the material creates a high level of steric bulk evenly dispersed through out the material, where each acid tends to be at least 6 to 8 carbons away from other acids at the closest, creating many shor t ethylene run lengths that are unable to crystallize in the dense hydroge n bonded matrix of the 22.2mol % acrylic aid copolymer. Figure 2-9. DSC overlay for ADMET EAA copolymers Thermogravimetric Analysis Figure 2-10 displays TGA curves fo r all seven ADMET and ROMP EAA copolymers synthesized through the prot ected monomer all exhibiting typical decomposition temperatures when compared to commercial EAA copolymers except for the ROMP EAA22.2 mol% copolymer that shows an initial weight loss at 300oC unique to this material. Copolymers below this molar composition of acid all show thermal

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55 stability well beyond 350oC under nitrogen, as expected for these materials. As a side note, the deprotection to the free acid copolymer can be confirmed by no loss of mass between 150 and 200oC where the hemiacetal ester undergoes a concerted cleavage reforming the vinyl ether and a protonated carboxylic acid. Figure 2-10 Thermogravimetric anal ysis of EAA copolymer series Conclusions The preparation of strictly linear EAA copolymers applying olefin metathesis polymerization techniques has been presented with primary structural characterization by FT-IR and NMR illustrating the effects of regular and random pendant group placement on spectroscopic analysis. The interacti on of GrubbsÂ’ ruthenium catalysts with carboxylic acid groups of certain monomers inhibited ADMET polymerization affording low molecular weight materials, whil e bulk ROMP copolymer izations yielded undesirable results with molecular weights dependant on acid content in the starting monomer mixture.

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56 Thermal properties and polymer morphology was examined applying DSC illustrating the dependence of peak melting temperature and heat of fusion to comonomer concentration and ethylene sequence lengt h distribution. ADMET-produced EAA copolymers show interesting behavior relati ve to previously synthesized materials indicating the drastic morphol ogical effects of extended hydrogen bonding in sequenced ethylene-based materials, where EAA21 displays semicrystall ine behavior while no discernable melting transitions were observed for EAA15 or EAA9 . ROMP-produced materials exhibited similar trends to those previously observed for low acid content EAA materials, but this study included EAA c opolymers with higher molar ratios of acid functionality allowing the determination of aci d content necessary (>13 mol %) to render RAOMP EAAs completely amorphous. Preliminary SAXS analysis of EAA21 copolymer has reveled interes ting scattering pattern s indicating the ordering of carboxylic acid dimers within the polymer matrix, possible included in the crystal phase of the polymer.

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57 CHAPTER 3 IONOMERS FROM SEQUENCED ETHYLEN E-ACRYLIC ACID COPOLYMERS Introduction The production and application of ethylen e-based ionomers over the past four decades has driven the in-depth structural analysis of these materials in search of the fundamental parameters regard ing ionic clustering and polym er crystallization. While the bulk morphology of ionomers is somewhat understood from a qualitative perspective and easily described in a th ree-phase model including ionic aggregates, amorphous polymer, and crystalline lamellae,92 the quantitative aspects regarding aggregate size, shape, and atomic content remain unknown. One factor creating di fficulty in ionomer characterization is the fact that the ethyleneco -acrylic acid (EAA) and ethyleneco methacrylic acid (EMAA) materials used in the preparation of ionomers included a myriad of structural features not controll ed during their preparation as described in Chapter 1. Herein, we report the app lication of sequenced EAA copolymers to the current challenge of ionomer characterization by the preparation of ionomeric materials containing exact placement of aci d functionality in the polyme r backbone with controlled ethylene sequence length between pendant branches. Synt hesis of ionomers in this manner allows production of structurally regular materials with unique bulk morphologies not observed in commercial systems.

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58 Experimental Materials Acid copolymers EAA9 , EAA15 , and EAA21 were prepared and isolated as reported in Chapter 2. Zinc acetate (99.99%), 1-butanol, dioxane, and methanol were purchased from Aldrich chemical and used as received unless othe rwise specified. Instrumentation and Analysis Differential scanning calorimetry (DSC) wa s performed using a Thermal Analysis Q1000 DSC at a heating rate of 10ºC/min. Ca librations were made using zinc and freshly distilled n -octane as the standards for peak temp erature transitions and zinc for the enthalpy standard. All samples were prepar ed in hermetically sealed pans (4-7 mg/sample) and were run using an empty pan as a reference. Thermogravimetric Analysis (TGA) was performed using a Th ermal Analysis Q500 TGA in dynamic highresolution mode. Samples sizes ranged fr om 5-10 mg. FT-IR measurements were performed on pressed and/or pulled films of the free acid copolymers and insoluble ionomers using a Bruker Vector 22 infrared spectrophotometer. General Neutralization Procedu re for Sequenced EAA Copolymers Zinc acetate (72 mg, 3.9 mmol) was dissolv ed in a 1:1 mixture of dioxane and 1butanol (30 mL) by stirring at 60oC overnight. Upon transfer to an addition funnel, the zinc solution was added quickly to a vigorously stirred solution of EAA21 (540 mg, 16.0mmol) in a 1:4 mixture of dioxane and 1-butanol (100 mL) at 90oC. A fine white precipitate was observed upon partial addi tion of salt solution, and upon complete addition, the cloudy mixture was allowed to stir for 3 hours. The reaction was cooled and methanol (200 mL) was added causing mo re precipitate formation and product coagulation. The mixture was allowed to stir for 15 minutes then, ionomer particles were

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59 filtered from the mixture, washed with warm methanol, and vacuum dried at 110C for 24 hours. All ionomers were stored under argon in a desiccator prior to analysis. EAA21Zn25 FT-IR: (cm-1) 2928, 2852, 1706, 1630, 1547, 1466, 1427, 942, 719. EAA21Zn50 FT-IR: (cm-1) 2928, 2852, 1705, 1630, 1547, 1465, 1427, 941, 721. EAA21Zn75 FT-IR: (cm-1) 2925, 2855, 1706, 1633, 1550, 1464, 1428, 940, 721. EAA15Zn25 FT-IR: (cm-1) 2938, 2851, 2679, 1737, 1706, 1631, 1549, 1466, 1429, 1330, 938, 721. EAA9Zn25 FT-IR: (cm-1) 2922, 2854, 2679, 1736, 1706, 1628, 1549, 1461, 1428, 1330, 945, 721. Results and Discussion Ionomer Design and Synthesis The sequenced free acid copolymers EAA9 , EAA15 and EAA21 described in Chapter 2 offer an excellent starting point for the preparation of ionomeric compounds while translating the structure control granted via ADMET polymerization into novel ionomers. This approach produces unique st ructures that may aid in the delineation of fundamental structure-property relationships concerning ethy lene sequence length, molar concentration of acid groups, and neutraliza tion level that remain unclear even after decades of research. Nomenclature for synthesized ionomers is based on parent copolymers, neutralization metal identity, a nd targeted neutraliz ation level assuming

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60 100% zinc acetate conversion. For example, EAA21Zn25 corresponds to the parent acid copolymer EAA21 reported in Chapter 2 with 25 mol% of the carboxylic acid functionality converted to zinc carboxylate. Neutralization of EAA21 was performed targeting 25, 50 and 75% conversi on of acid functionality, while EAA9 and EAA15 were only neutralized at 25% due to the highly f unctionalized nature of these materials. Preliminary structural and thermal analysis of ionomer structures using FT-IR, SAXS, DSC and TGA will be presented. Neutralization of Sequenced EAA Copolymers Figure 3-1 illustrates the neutralization reac tion used to prepare all ionomers reported in this chapter. Effectively an anionic exchange reaction on the zinc metal center, an acetate salt solution is mixed with an EAA copolymer solution generating a sequenced ionomer upon conversion of the acetat e to acetic acid and ionic binding of the zinc center to the polymer chain. This re action can be monitored visually due to the partial insolubility of the reaction products, and upon d ilution of the reaction mixture with methanol, sequenced ionomers were easily isolated by filtration. OH O n n OH O x yOO Zn2+ Zn(OAc)21-butanol, dioxane EAA9EAA9Zn25 Figure 3-1. Sequenced EAA ionomer synthesis Ionomer Analysis The insolubility of sequenced ionomers prepar ed in this study precludes them from many types of structural analysis that have been readily applied to the soluble acid copolymers. Most importantly, the determina tion of neutralization le vel is important as varying cation concentration may lead to va riable aggregate features. Herein, the

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61 application of FT-IR and DSC as the prim ary tools for ionomer characterization is discussed along with significant differences in our materials relative to commercial ionomers. Preliminary small angle x-ray scattering (SAXS) and scanning transmission electron microscopy (STEM) data will be pr esented, although conclusions from these analyses are not fully developed as the wait fo r more detailed characterization data from collaborators continues. FT-IR Analysis FT-IR is a powerful tool for ionomer char acterization as strong absorbances from the various carboxylic acid and carboxylate functionality interact strongly in the IR region of the spectrum.93, 95 Previous absorbance studies on commercial ionomers have been successful in material characterization, but the nature of the analysis detailing only chemical bonding and vague interpretations of polymer morphology leaves much to the imagination concerning bul k ionomer morphology. Sequenced ionomers were difficult to an alyze due to their insolubility and extremely resilient bulk morphology. To ac quire samples of desired thickness, heat pressing films at 150oC and subsequent hot air drawing wa s used to isolate thin sections of drawn ionomer sheets with a relatively large degree of IR transparency in nonabsorbing regions of the spectrum. Over all, uniform sample thickness was easily acquired for most samples, but EAA9Zn25 and EAA15Zn25 were very difficult to analyze as the higher levels of functionalization along with the subsequent neutralization yield tough, glassy materials. Absorbance data for isolated ionomers supports notion of successful ionomer synthesis due to the appearance of multiple new absorbances associated with zinc carboxylate species upon neutra lization. Bands at 1550cm-1 and 1631cm-1, not present in

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62 FT-IR data from parent EAA copolymers, are observable for all ionomers prepared in this chapter indicating successful neutralization regardless pare nt copolymer acid content. Thermal Analysis The thermal analysis of ionomeric compounds had been used to identify semicrystalline materials and track the effect of neutralization on polymer glass transition temperatures and peak melting points. In a recent report, the sl ow room-temperature annealing of EMAA ionomers is discussed indicating the significant effects that ionic aggregates have both on the pe rturbation of crystal forma tion but also concerning the dynamic nature of ionomer morphology whereb y they can slowly a lter their secondary structure of the materi al upon long-term storage.103 DSC analysis of sequenced EAA materials indicated similar features observable in first scans of a material but were non-re producible under dynamic scanning conditions. Figure 3-2 illustrates the first scans of E AA ionomers compared to their parent EAA copolymers after vacuum drying near 100oC and storing at room temperature for one month. Examination if the thermal responses for the EAA21 series of materials indicates all ionomers exhibit some form of crystal me lting in the first scan DSC data, up to 75% neutralization. This data indicates the regular structure of sequenced ionomers is creating order in the bulk state unlike what is observed for the typi cal industrial ionomers shown in Figure 1-12 where melting profile differs little from the free acid copolymer up to 78% neutralized ionomer. For commercial ma terials, the low incorporation of acid functionality combined with the random dist ribution of ethylene sequence lengths allows extensive chain folding and lamellar formation regardless of neutralization level. In sequenced materials with controlled run leng ths, the acid group is evenly spaced along the polymer chain leading to an even di stribution of ionic gr oups along the chain

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63 impeding crystallization through out the entire material rather than just chain segments closely bonded to carbox ylates or free acids. The bimodal nature of the thermal profiles for the EAA21 series of ionomeric materials is indicative of multiple transitions, possibly relaxations or melting events, although this can only be speculated without pr oper SAXS analysis. Even without this critical analysis of secondary structure, th e correlation of the initial transition in the bimodal melt to the melting transition in the acid is clear, lending the second peak in the DSC melting profile to be associated with a higher melting crystal form due to the neutralization of the materi al. Although these results may indicate possible polymer crystallization involving both the free acid a nd the ionic portion of the material into different crystal forms, another possible explanation is the decrease in overall crystallinity due to clustering of ionic groups impeding polymer crystallization, as well as the observation of a glass transition temperature, possibly hidden in EAA21 analysis by a large premelting event. Upon increasing neutrali zation level, the relati ve intensity of this endothermic transition is reduced while th e initial relaxation, a glass transition temperature, is also reduced in thermal capac ity due to increased strain imparted on the material by higher concentrati ons of ionic clusters. First scan analysis of EAA9 and EAA15 free acids and respective ionomers is also included in Figure 3-2. Clear ly seen for both free acids are the respective glass transition temperatures for both copolymers at 21.9 and -3.8oC. Upon neutralizat ion, observation of the glass transition temperature is difficult due to the excess strain imparted on the material by ionic clustering, but a clear relaxation can be seen for EAA15Zn25 at 49oC where no observable relaxation can be distinguished for EAA9Zn25 .

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64 Figure 3-2. First cycle heating curves for DSC of ADMET free acid and ionomer materials after storage at room temperature for two months Second scans for the ionomers produce mu ch less in the form of structural information where all materials exhibite d amorphous behavior upon dynamic scanning at 10oC/min. The endothermic tr ansitions observed for the EAA21 series of ionomers in Figure 3-2 are no longer presen t in Figure 3-3 where only s light relaxations can be observed associated with the glass trans ition temperature of the ionomers showing reduced transition intensity, although exhibiting the similar temperatures for the relaxations. Both free acid c opolymers and sequenced ionomers EAA9Zn25 and EAA15Zn25 show little difference upon comparison of first and second scan analysis in DSC, exhibiting minor relaxations at best.

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65 Figure 3-3. Second cycle heating curves fo r the DSC of ADMET free acid and ionomer materials As mentioned previously, the determinati on of neutralization le vel is difficult in ethylene based ionomers due to their inherent in solubility and lack of accurate techniques for the quantitative determination of low c oncentration metal species embedded in an irregular polymer matrix. One fairly subjective method for determination of metal content, useful only when applied in a comp arative fashion, is the thermogravimetric (TGA) analysis of ionomeric materials. Due to the fact that few literature reports contain discussion concerning TGA of commercial ma terials, Surlyn™ and Nucrel™ materials were analyzed and data is pr esented in Figure 3-4 as a collection of mass loss curves from 100-800oC.

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66 Figure 3-4. Thermogravimetric analysis of Nucrel™ and Surlyn™ EMAA materials Upon thermal decomposition in a nitrogen atmosphere, all organic components should be removed by pyrolytic action leaving a residue corresponding on ly to zinc metal salts and other possible contaminants. While the chemical composition of the remnants can be debated, there is no doubt that a ll metal originally di spersed throughout the polymer should still remain in the final ma ss analysis and, due to similar synthetic approaches, the chemical structure of such re sidue should be uniform across all ionomers. As illustrated by the residue analysis at 750oC in Figure 3-4, an in crease in mass percent residue is observed relative to targeted neutralizati on levels of the ionomer. Figure 3-5 illustrates the TGA of EAA21 ionomers described in this chapter including mass percent residue at 750oC. Similar to commercial materials, EAA21 ionomers represent an increase in mass percen t residue based on targ eted neutralization level, however, preliminary analysis indicates targeted neutralization levels are not being

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67 achieved for EAA21Zn50 and EAA21Zn75 most likely attributed to ionomer insolubility causing precipitation prior to completion of the neutralization reaction. Figure 3-5. Thermogravimetric analysis fo r sequenced EAA21 ionomers and the parent EAA21 copolymer Preliminary Secondary Structural Analysis In an ongoing collaboration with Professo r Karen Winey at the University of Pennsylvania, the analysis of sequenced i onomers has been performed using small-angle x-ray scattering (SAXS) and scanning tr ansmission electron microscopy (STEM). Although preliminary data has be en obtained confirming the pres ence of ionic aggregates also supporting our FT-IR analysis and inhere nt insolubility in common solvents, we present the following SAXS and STEM data more as a preview to what we expect from subsequent careful analysis of the entire family of ionomers.

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68 STEM analysis of EAA21Zn25. STEM analysis has allowed direct imagi ng of ionic aggregates in commercial ionomers relying on the atomic number difference between metal atoms and all other atoms in the material. Dense nuclei of meta l centers scatter incident electrons at far greater intensity than less dense nuclei, and upon data manipulation, is visualized as a two-dimensional projection of the three-dimens ional material density map. As expected, sample thickness is an important factor fo r ionomer imaging tat must be addressed and held uniform prior to cross material comparison. Figure 3-6 displays STEM images generated from EAA21Zn50 . Here again, this is only preliminary analysis, but was included in the dissertation due to the overwhelming support of synthetic claims in previous secti ons. In both images, small ionic aggregates can be seen evenly dispersed throughout the material at roughly 4 nm in diameter and fairly monodisperse aggregate diameter. These features, also reported for several commercial copolymers,100, 104, 115, 116 prove not only the neutra lization of sequenced EAA materials, but represent the first visual evidence of ionic aggregate formation in sequenced EAA ionomers. Figure 3-6. STEM images for EAA21Zn50

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69 SAXS analysis of EAA21Zn25. SAXS analysis of a wide variety of i onomeric materials has been performed as researchers probe commercial materials to delineate ionic clustering phenomena as associated with polymer crystallinity.94, 98 Figure 3-7 shows a side -by-side comparison of SAXS data for a commercial Surlyn ionomer, EAA21Zn50 , and their respective parent acid copolymers. The data for the Nucrel c opolymer clearly indicates the presence of amorphous and crystalline regions of the hydr ocarbon backbone by the appearance of an broad halo from amorphous scattering overlap ping with a sharp reflection attributed to polyethylene-like lamellae. Upon neutraliza tion, the sharp reflection and amorphous halo broaden with the appearance of a new amorphous halo attributed to ionic aggregates dispersed throughout the polymer matrix. The scattering pattern for EAA21 copolymer is included here for reference with extended discussion on the free acid copolymer included in Chapter 2. The significant morphology differences between commercia l ethylene copolymers and saturated ADMET copolymers can be resolved as EAA21 exhibits a broad halo similar to Nucrel, but also indicates long -range ordering by the presence of a scattering halo near the origin of the diagram. Here again, the structur al regularity achieved in ADMET polymerization is indicative of novel polymer morphologies based on se quence length control and precise functional group placemen t. Upon neutralization of EAA21 to EAA21Zn50 , little changes with re spect to the amorphous scattering fr om the polymer backbone occur, and the appearance of an amorphous halo, sim ilar to that seen for Surlyn™, indicates successful neutralization for EAA21 . Interestingly, the amorphous scattering halo attributed to ionic aggr egates is overlapped in EAA21Zn50 by an intense scattering at the

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70 same length scale that suggest possible ordering of ionic species due to the regular structure associated with ADMET materials. Figure 3-7. Comparison of SA XS scattering profiles for commercial materials (Nucrel™ and Surlyn™) and sequenced analogs ( EAA21 and EAA21Zn50 ) Conclusion In summary, the preparation of sequen ced ionomers has been performed by the development of solution ne utralization procedures fo r sequenced EAA copolymer described in Chapter 2. Structural anal ysis of all materials by FT-IR indicates neutralization regard less of acid content in the parent copolymer, and thermal analysis by DSC and TGA also suggest successful neutra lization. Interesti ngly, thermal profiles indicate increased order for in EAA21 ionomers upon first temperature scans, but

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71 amorphous responses were observed for all seven materials upon second temperature ramps. Preliminary STEM and SAXS analysis of one sample, EAA21Zn50 , also suggests neutralization while indicating th e presence of novel EAA ionomer morphology that may be causing ordering of the i onic clusters throughout the material.

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72 CHAPTER 4 LINEAR ETHYLENE-VINYL ETHER COPOLYMERS: SYNTHESIS AND THERMAL CHARACTERIZATION Introduction The copolymerization of ethylene with alkyl vinyl ethers is difficult due to the nearly infinite reactivity rati os of the two vinyl monomers117 and the ability of alkyl vinyl ethers to act as efficient chain tr ansfer agents during polymerization.118 In a small number of dated US patents,118-126 the application of hi gh pressure free radical copolymerization techniques yi elded branched, highly variab le reaction products from viscous liquids to brittle solids with proposed industrial applications from adhesives to barrier materials (Table 4-1). While high molecular weight copolymers were reported in some cases, the typically low levels of vinyl ether incorporation lead to marginal differences in bulk properties relative to polyethylene prepar ed under similar conditions. Early reports indicated successful incorpor ation of both monomers, but forcing conditions of high temperatures and pressures were required usi ng either free-radical in itiation or what is referred to as Friedel-Crafts polymeri zation with an Al or Ti catalyst. 118-124 Recent advancements in late transition metal nickel catalysis have allowed the preparation of a few examples of ethyleneco -vinyl ether (EVE) copolymers at milder conditions with more controllable results.125, 126 Although sample characteriza tion data is limited in the patent literature, synthetic methodology and re ported data are compiled in Table 4-1 as a

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73 short review of EVE synthesis illustrating the range of materi al properties available when applying different chain c opolymerization techniques. Table 4-1. U.S. Patent s pertaining to ethyleneco -vinyl ether materials Polymerization Conditions U.S. Patent Comonomer CH2=CH-O-R (R =) Mol % Vinyl Ether In Copolymer CatalystaPressure (Kpsi) Temperature ( C) Copolymer Productsb 2467234 ( 1949 ) 119 C1, C2, Ph Not reported R 0.7-50 20-400 solids 2748170 (1956)120 C1-C16 11.2 (C4) R, FC 0.4-1.1 150 400-700 g/mol 3025267 (1962)123 CH2(CH2)nOH n = 1-5 2-14 R 15-50 100-200 10-100 Kg/mol 3026290 (1962)122 C1-C16 5-80 FC 0.500-50 35 liquids and solids 3033840 (1962)118 CH3 0.5-10 R 12-30 150-240 solids 3226374 (1962)121 C1-C10 1.8-2.6 R 15-80 160-250 solid films 3560463 (1971)124 C15, C18 0.6-1.3 R 20-30 150-240 solid films 4906754 (1987)125 4698403 (1990)126 C2 1.4 Ni cat. 0.06 65 solids a) R = free radical (ROOR and/or O2 initiators), FC = Friedel-Crafts (Al or Ti catalyst); b) as published, molecular weight data included when reported As with all polyolefins, bulk EVE prope rties are highly dependant on polymer microstructure including comonomer ratios, th e degree of branching, and especially the presence or lack thereof extended, crystal lizable ethylene run lengths in the material.91, 107 Linear high molecular weight EVE copolymer s with low vinyl ether content exist as tough, semicrystalline materials resembling high density polyethyl ene while branched, highly functionalized, or low mo lecular weight EVE materials exist as viscous, adhesive liquids. Although EVE synthesis can be modi fied to yield desired materials through proprietary chain copolymeri zation methodology, reactivity ratio and chain transfer issues create difficulties in isolating pure c opolymer microstructures. The application of metathesis chemistry to the challenge of EVE synthesis allows preparation of linear macromolecules with a priori control over comonomer incorporation and pendant ether

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74 branch location, as previously reported in the synthesis of a sequenced ethyleneco methyl vinyl ether copolymer.114 Herein, we report the synthesis and therma l characterization of a family of six linear EVE copolymers including three poly(ethyleneco -methyl vinyl ether) (EMVE) and three poly(ethyleneco -ethyl vinyl ether) (EEVE) materials through a well-known metathesis polymerization\hydrogenation methodology.6, 7 This approach yields sequenced EVE copolymers with monodisperse ethylene run lengths between pendant branches, and structural char acterization via NMR and FT-IR techniques illustrates the ability to isolate exact polymer microstr uctures while evenly spacing pendant ether branches along the polyethyl ene chain at intervals of 11, 14 and 21 backbone carbons. Thermal analysis via differential scanning calor imetry (DSC) demonstr ates the effect of controlled copolymer struct ure and defined ethylene r un lengths on bulk material morphology and polymer crystallization. Experimental Materials All reagents were purchased from Aldric h chemical and used as received unless otherwise specified. Ethyl format e was freshly distilled from MgSO4 before use, and 5bromo-1-pentene, 8-bromo-1-octene, 11-chloro-1-undecene127 and SchrockÂ’s molybdenum catalyst ([(CF3)2CH3CO]2(N-2,6-C6H3i Pr2)Mo=CHC(CH3)2Ph)128 were synthesized according to literature procedures. Instrumentation and Analysis All 1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were recorded on a Varian Associates Mercury 300 spec trometer. Chemical shifts for 1H and 13C NMR were referenced to residual signals from CDCl3 (1H = 7.27 ppm and 13C = 77.23 ppm) with

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75 0.03% v/v TMS as an internal reference. Reaction conversions and relative purity of crude products were monitored by thin la yer chromatography (TLC) performed on EMD silica gel coated (250 m thickness) glass plates and 1H NMR. Developed TLC plates were stained with iodine abso rbed on silica or vanillin solu tion (5 wt% in 50mL ethanol with 2mL H2SO4) to produce a visible signature. Low and high-resolution mass spectral (LRMS and HRMS) data were obtained on a Finnegan 4500 gas chromatograph/mass spectrometer using the chemi cal ionization (CI) mode. Differential scanning calorimetry (DSC) an alysis was performed using a PerkinElmer DSC-7 equipped with a controlled coolin g accessory (CCA-7) at a heating rate of 10ºC/min. Calibrations were made using indium and freshly distilled n -octane as the standards for peak temperature transitions and indium for the en thalpy standard. All samples were prepared in hermetically sealed pans (4-7 mg/sample) and were run using an empty pan as a reference and empty cells as a subtracted baseline. Gel permeation chromatography (GPC) was performed at 40 C using a Waters Associates GPCV2000 liquid ch romatography system with an internal differential refractive index detector (D RI) and two Waters Styragel HR-5E columns (10 microns PD, 7.8 mm ID, 300 mm length) in HPLC grade tetrahydrofuran as the mobile phase at a flow rate of 1.0 mL/minute. Injections were made at 0.05-0.07 % w/v sample concentration using a 220.5 l injection volume. Retention times were calibrated against narrow molecular weight polystyrene standa rds (Polymer Laboratories; Amherst, MA) selected to produce Mp and Mw values below and above the expected copolymer molecular weight.

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76 General Procedure for Grignard Reaction with Alkenyl Chlorides or Bromides A solution of the 6-bromo-1-hexene (2.2 eq .) in THF (2M) was added dropwise to freshly scoured magnesium turnings (2.3 eq .) in a flame dried 250 mL round bottom flask and allowed to reflux for one hour under a bl anket of argon gas. A solution of ethyl formate (1.0 eq.) in THF (2 M) was added to the flask via addition funnel over twenty minutes. Upon complete addition, the reacti on was bought back to reflux for a period of 16 hours. The reaction was quenched via additi on of water (50 mL), and dissolved into a biphasic system upon addition of ether (100mL) . The crude reaction mixture was then washed with water (2 x 100mL) and brine (2 x 50 mL), and the organic layer was concentrated by rotary evaporation to colorless oil. OH 4 4 1,12-tridecadiene-7-ol (4-1) Column chromatography using 4:1 hexane:d ichloromethane as the eluent afforded 4.5 g of a colorless oil after so lvent evaporation (63% yield). 1H NMR (CDCl3): (ppm) 1.24-1.52 (br, 12H), 2.07 (q, 4H), 3.59 (b r, 1H), 4.98 (m, 4H), 5.81 (m, 2H); 13C NMR (CDCl3): (ppm) 25.33, 29.15, 33.94, 37.51, 72.05, 114.57, 139.10; CI/HRMS: [M+H]+ calcd. for C13H25O: 197.1905, found: 197.1910; Elemental analysis calcd. for C13H24O: 79.53 C, 12.32 H; found: 79.36 C, 12.44 H. OH 6 6 1,16-heptadecadiene-9-ol (4-2) From 8-bromo-1-octene. Column chroma tography using 9:1 hexane:diethyl ether as the eluent afforded 5.1 g of colorless oil (65% yield). 1H NMR (CDCl3): (ppm)

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77 1.22-1.51 (br, 20 H), 2.05 (q, 4H), 3.59 (b r, 1H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 25.82, 29.80, 29.31, 29.76, 33.98, 37.68, 72.18, 114.37, 139.33; CI/HRMS: [M+H]+ calcd. for C17H33O: 253.2531, found: 253.2534; Elemental analysis calcd. for C17H32O: 80.88 C, 12.78 H; found: 80.74 C, 12.69 H. OH 9 9 1,22-tricosadiene-12-ol (4-3) From 9-chloro-1-undecene. Column ch romatography using 9:1 hexane:diethyl ether as an eluent afforded 15.4 g of a white solid (92% yield). 1H NMR (CDCl3): (ppm) 1.20-1.50 (br, 32H), 2.04 (q, 4H), 3. 59 (m, 1H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 25.87, 29.15, 29.35, 29.70, 29.77, 29.83, 29.92, 34.03, 37.7, 72.22, 114.30, 139.44; CI/HRMS: [M]+ calcd. for C23H44O: 336.3392, found: 336.3392; Elemental analysis calcd. for C23H44O: 82.07 C, 13.18 H; found: 82.11 C, 13.36 H. General Alkylation Procedu re for the Preparation of ,–Diene Ethers A solution of 1 (1 eq.) in DMF was added to a slurry of NaH (1.5 eq.) in DMF in a 250 mL three neck flask. Methyl iodide (1.5 eq.) was added slowly via syringe and the solution was allowed to stir at room temper ature for 1 hour. The reaction was heated to 50C for 3 hours, then cooled and quenched via addition of water (25 mL). Following extraction with diethyl ether and washing with brine, the ether solution was concentrated to yellow oil.

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78 OMe 4 4 7-methoxy-1,12-tridecadiene (4-4) Column chromatography using 17:3 hexa ne:dichloro methane as the eluent afforded 2.3g of colorless oil (67% yield). 1H NMR (CDCl3): (ppm) 1.21-1.52 (br, 12H), 2.05 (q, 4H), 3.13 (m, 1H), 3.31 (s , 3H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 24.97, 29.37, 33.98, 56.57, 81.05, 114.48, 139.18; CI/HRMS: [M+H]+ calcd. for C14H27O: 211.2061, found: 211.2067; Elemental analysis calcd. for C14H26O: 79.94 C, 12.46 H; found: 80.62 C, 12.74 H. OMe 6 6 9-methoxy-1,16-heptadecadiene (4-5) From 2 . Column chromatography using 9:1 he xane:dichloro methane as the eluent afforded 3.4g of colorless oil (71% yield). 1H NMR (CDCl3): (ppm) 1.20-1.51 (br, 20H), 2.05 (q, 4H), 3.11 (m, 1H), 3.32 (s , 3H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 25.44, 29.10, 29.36, 29.93, 33.65, 34.00, 55.58, 81.19, 114.34, 139.37; CI/HRMS: [M+H]+ calcd. for C18H35O: 267.2687, found: 267.2688; Elemental analysis calcd. for C18H34O: 81.13 C, 12.86 H; found: 80.95 C, 12.97 H. OMe 9 9 12-methoxy-1,22-tric osadiene (4-6) From 3 . Column chromatography using 7:3 he xane:dichloro methane as the eluent afforded 7.3g of colorless oil (78% yield). 1H NMR (CDCl3): (ppm) 1.20-1.50 (br, 32H), 2.05 (q, 4H), 3.12 (m, 1H), 3.32 (s, 3H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR

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79 (CDCl3): (ppm) 25.50, 29.17, 29.37, 29.72, 29.79, 29.86, 30.11, 33.67, 34.04, 56.59, 81.24, 114.30, 139.48; CI/HRMS: [M+H]+ calcd. for C24H47O: 351.3626, found: 351.3616; Elemental analysis calcd. for C24H46O: 82.21 C, 13.22 H; found: 82.10 C, 13.46 H. OEt 4 4 7-ethoxy-1,12-tridecadiene (4-7) From 1 . Column chromatography using 17: 3 hexane:dichloro methane as the eluent afforded 1.4g of co lorless oil (62% yield). 1H NMR (CDCl3): (ppm) 1.19 (t, 3H), 1.21-1.52 (br, 12H), 2.05 (q, 4H), 3.21 (m , 1H), 3.48 (q, 2H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 15.91, 25.17, 29.36, 34.17, 64.31, 79.44, 114.46, 139.26; CI/HRMS: [M+H]+ calcd. for C15H29O: 225.2218, found: 225.2223; Elemental analysis calcd. for C15H28O: 80.29 C, 12.58 H; found: 80.25 C, 12.61 H. OEt 6 6 9-ethoxy-1,16-heptadecadiene (4-8) From 2 . Column chromatography using 9:1 he xane:dichloro methane as the eluent afforded 2.3g of colorless oil (69% yield). 1H NMR (CDCl3): (ppm) 1.19 (t, 3H), 1.21-1.52 (br, 20), 2.05 (q, 4H), 3.20 (br, 1H), 3.48 (q, 2H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 15.92, 25.64, 29.12, 29.36, 29.93, 34.02, 34.37, 64.31, 79.57, 114.34, 139.41; CI/HRMS: [M+H]+ calcd. for C19H37O: 281.2844, found: 281.2838; Elemental analysis calcd. for C19H36O: 81.36 C, 12.94 H; found: 81.32 C, 13.02 H.

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80 OEt 9 9 12-ethoxy-1,22-tricosadiene (4-9) From 3 . Column chromatography using 9:1 he xane:dichloro methane as the eluent afforded 1.8g of colorless oil (67% yield). ). 1H NMR (CDCl3): (ppm) 1.19-1.49 (br, 35), 2.05 (q, 4), 3.18 (m, 1H), 3.48 (q, 2H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 15.94, 25.70, 29.18, 29.38, 29.73, 29.81, 29.88, 30.11, 34.06, 34.37, 64.27, 79.59, 114.28, 139.43; CI/HRMS: [M+H]+ calcd. for C25H49O: 365.3783, found: 365.3792; Elemental analysis calcd. for C25H48O: 82.34 C, 13.27 H; found: 82.37 C, 13.48 H. General ADMET Polymerization Proce dure for Symmetrical Ether Monomers Purified monomer 4 was distilled onto a potassium metal mirror and allowed to sit for 2 hours or until noticeable reaction ceased . Upon vacuum transfer into a 50 mL Schlenk flask, the monomer was taken into an Argon filled glove box, mixed with SchrockÂ’s [Mo] catalyst (2000:1 monomer:cat alyst, ~1.5 g monomer) in a 50mL round bottom flask, and magnetically stirred until ethylene evolution waned and reaction viscosity increased. The polymer ization flask was then sealed with a Schlenk adapter and transferred out of the glove box and onto a hi gh vacuum line. Intermittent vacuum was applied over 4 hours at room temperature wh ile the reaction conti nued to exhibit easily detectable ethylene producti on and viscosity increase. Once the reaction slowed, the golden amorphous liquid was warmed to 45C and allowed to stir for three days under high vacuum (10-4 torr). Upon cooling to room temperature, the dark yellow polymerization was quenched by opening the fl ask to lab atmosphere and adding 25 mL of toluene. The solution was stirred until a dark green color arose (Mo oxides), flashed

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81 over a 1” pad of alumina to remove catalys t residue, and concentrated to yield the unsaturated copolymer as viscous oil. OMe 4 4 n Polymerization of 7-methoxy1,12-tridecadiene (4-10) 1H NMR (CDCl3): (ppm) 1.20-1.52 (br, 12H), 1.98 (br, 4H), 3.12 (br, 1H), 3.31 (s, 3H), 5.40 (br, 2H); 13C NMR (CDCl3): (ppm) 25.04, 30.11, 32.82, 33.51, 56.57, 81.10, 130.01 ( cis olefin), 130.50 ( trans olefin); IR (, cm-1): 2930, 2854, 1460, 1369, 1097, 966, 729; GPC data (THF vs . polystyrene standards): Mw = 14853 g/mol; P.D.I. (Mw/Mn) = 1.79. OMe 6 6 n Polymerization of 9-methoxy1,16-heptadecadiene (4-11) 1H NMR (CDCl3): (ppm) 1.19-1.52 (br, 20H), 1.97 (q, 4H), 3.12 (m, 1H), 3.32 (s, 3H), 5.39 (br, 2H); 13C NMR (CDCl3): (ppm) 25.47, 29.39, 29.83, 29.96, 32.80, 33.67, 56.56, 81.18, 130.04 ( cis olefin), 130.64 ( trans olefin); IR (, cm-1): 2928, 2854, 1462, 1367, 1095, 966, 725; GPC data (THF vs. polystyrene standards): Mw = 31284 g/mol; P.D.I. (Mw/Mn) = 1.73. OMe 9 9 n Polymerization of 12-methoxy-1,22-tricosadiene (4-12) 1H NMR (CDCl3): (ppm) 1.19-1.52 (br, 32H), 1.97 (q, 4H), 3.12 (m, 1H), 3.32 (s, 3H), 5.39 (br, 2H); 13C NMR (CDCl3): (ppm) 25.50, 29.42, 29.75, 29.84, 29.89, 30.13, 32.85, 33.65, 56.58, 81.21, 130.08 ( cis olefin), 130.54 ( trans olefin); IR (, cm-1):

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82 2926, 2853, 1464, 1367, 1097, 966, 721; GPC data (THF vs. polystyrene standards): Mw = 81350 g/mol; P.D.I. (Mw/Mn) = 2.54. OEt 4 4 n Polymerization of 7-ethoxy-1,12-tridecadiene (4-13) 1H NMR (CDCl3): (ppm) 1.10-1.52 (br, 15H), 1.98 (br, 4H), 3.12 (br, 1H), 3.47 (q, 2H), 5.40 (br, 2H); 13C NMR (CDCl3): (ppm) 15.93, 25.24, 30.11, 32.83, 34.22, 64.28, 79.50, 130.02 ( cis olefin), 130.51 ( trans olefin); IR (, cm-1): 2930, 2856, 1460, 1371, 1344, 1101, 966, 731; GPC data (THF vs. polystyrene standards): Mw = 24114 g/mol; P.D.I. (Mw/Mn) = 1.65. OEt 6 6 n Polymerization of 9-ethoxy-1,16-heptadecadiene (4-14) 1H NMR (CDCl3): (ppm) 1.20-1.50 (br, 23H), 1.97 (q, 4H), 3.20 (m, 1H), 3.47 (q, 2H), 5.39 (br, 2H); 13C NMR (CDCl3): (ppm) 15.93, 25.64, 29.43, 29.86, 29.97, 32.82, 34.40, 64.28, 79.58, 130.39 ( cis olefin), 130.53 ( trans olefin); IR (, cm-1): 2927, 2854, 1462, 1371, 1344, 1105, 966, 725; GPC data (THF vs. polystyrene standards): Mw = 48938 g/mol; P.D.I. (Mw/Mn) = 1.74. OEt 9 9 n Polymerization of 12-ethoxy-1,22-tricosadiene (4-15) 1H NMR (CDCl3): (ppm) 1.19-1.52 (br, 35H), 1.97 (br, 4H), 3.20 (m, 1H), 3.47 (q, 2H), 5.38 (br, 2H); 13C NMR (CDCl3): (ppm) 15.92, 25.69, 29.41, 29.75, 29.78, 29.84, 29.89, 20.11, 32.84, 34.36, 64.27, 79.60, 130.07 ( cis olefin), 130.531 ( trans

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83 olefin); IR (, cm-1): 2927, 2853, 1464, 1371, 1344, 1110, 966, 721; GPC data (THF vs. polystyrene standards): Mw = 9698 g/mol; P.D.I. (Mw/Mn) = 1.91. Hydrogenation of Unsaturated ADMET Polymers The crude polymer solution of 4-10 was transferred to a Parr Bomb glass sleeve and diluted to ~200 mL with toluene. Palladium (10% on carbon, 100mg) was added to the solution, and the sleeve was sealed insi de a Parr Bomb equipped with a mechanical stirrer and temperature cont rol. The vessel was purged three times with 1000 psi hydrogen gas, then filled to 1000 psi and heated to 100C for 2 days. Upon depressurization and cooling, the crude reaction mixture was vacuum filtered over a plug of neutral silica, then con centrated to viscous liquid. n OMe EMVE11 (4-16) 1H NMR (CDCl3): (ppm) 1.20-1.52 (br, 20H), 3.12 (br, 1H), 3.32 (s, 3H); 13C NMR (CDCl3): (ppm) 25.53, 29.87, 29.89, 30.14, 33.71, 56.57, 81.24; IR (, cm-1): 2927, 2853, 1464, 1371, 1344, 1110, 721; GPC data (THF vs. polystyrene standards): Mw = 15309 g/mol; P.D.I. (Mw/Mn) = 1.52. OMe EMVE15 (4-17) 1H NMR (CDCl3): (ppm) 1.22-1.53 (br, 28H), 3.12 (m, 1H), 3.32 (s, 3H); 13C NMR (CDCl3): (ppm) 25.53, 29.91, 30.14, 33.70, 56.58, 81.25; IR (, cm-1): 2920, 2851, 1466, 1369, 1099, 723; GPC data (THF vs. polystyrene standards): Mw = 24940 g/mol; P.D.I. (Mw/Mn) = 1.70.

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84 OMe EMVE21 (4-18) 1H NMR (CDCl3): (ppm) 1.20-1.50 (br, 40H), 3.12 (m, 1H), 3.32 (s, 3H); 13C NMR (CDCl3): (ppm) 25.51, 29.96, 30.14, 33.66, 56.60, 81.22; IR (, cm-1): 2918, 2851, 1470, 1367, 1261, 1097, 804, 719; GPC data (THF vs. polystyrene standards): Mw = 74132 g/mol; P.D.I. (Mw/Mn) = 2.27. n OEt EEVE11 (4-19) 1H NMR (CDCl3): (ppm) 1.20-1.50 (br, 23H), 3.20 (m, 1H), 3.48 (q, 2H); 13C NMR (CDCl3): (ppm) 15.94, 25.73, 29.88, 29.91, 30.13, 34.41, 64.28, 79.62; IR (, cm-1): 2926, 2854, 1464, 1372, 1344, 1111, 721; GPC data (THF vs. polystyrene standards): Mw = 25632 g/mol; P.D.I. (Mw/Mn) = 1.64. n OEt EEVE15 (4-20) 1H NMR (CDCl3): (ppm) 1.20-1.50 (br, 31H), 3.20 (m, 1H), 3.48 (q, 2H); 13C NMR (CDCl3): (ppm) 15.94, 25.73, 29.93, 30.13, 34.41, 64.28, 79.62; IR (, cm-1): 2926, 2852, 1466, 1371, 1344, 1113, 721; GPC data (THF vs. polystyrene standards): Mw = 43082 g/mol; P.D.I. (Mw/Mn) = 1.75. OEt n EEVE21 (4-21) 1H NMR (CDCl3): (ppm) 1.20-1.50 (br, 40H), 3.12 (m, 1H), 3.32 (s, 3H); 13C NMR (CDCl3): (ppm) 15.94, 25.70, 29.94, 30.12, 34.37, 64.27, 79.61; IR (, cm-1):

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85 2924, 2853, 1466, 1372, 1344, 1261, 1111, 804, 721; GPC Data (THF vs. polystyrene standards): Mw = 11,563 g/mol; P.D.I. (Mw/Mn) = 1.58. Results and Discussion Polymer Design and Synthesis Applying our method of preci sion polyolefin synthesis6 to the preparation of EVE materials affords linear copolymers with pe ndant alkyl ether groups evenly spaced along the polymer backbone.114, 129 To easily describe these materials, nomenclature is based on parent chain addition mono mers and ether branch frequency. For example, EMVE21 stands for ethylene ( E ) and methyl vinyl ether ( MVE ), the two comonomers, and the number 21 refers to the branch frequency for each pendant methoxy group. Ethyleneco -ethyl vinyl ethers bearing the prefix EEVE were also synthesized for this study, and three examples of each copolymer have been prepared with pendant ether branches every 11 , 15 , and 21 carbons. These materials can be c onsidered sequenced EVE copolymers at different comonomer ratios with 4.5, 6.5, and 9.5 units of ethylene, respectively, between each vinyl ether m onomer in the copolymer. Synthesis of symmetrical ether bearing , –diene monomers for ADMET polymerization begins with the double Grigna rd addition of various alkenyl bromides onto ethyl formate affording a family of dien e alcohols (Figure 4-1). Once converted to alkyl ethers, diene monomers are polymer ized with Schrock’s molybdenum catalyst yielding high molecular wei ght, unsaturated copolymers. Exhaustive hydrogenation of the remaining olefin via Parr techniques affords strictly linear EVE copolymers with exact ether branch frequency along the pol ymer backbone. Isolated EVE copolymers exist as colorless, viscous liquids with the exception of EMVE21 and EEVE21 which are low melting, semicrystallin e solids at ambient conditions.

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86 OH x x OMe x x x = 4 ( 4-1 ) 6 ( 4-2 ) 9 ( 4-3 ) OEt x x OMe x x n OEt x x n i iii iii ii iv iv OMe n n OMe n OMe OEt n n OEt n OEt x = 4 ( 4-4 ) 6 ( 4-5 ) 9 ( 4-6 ) x = 4 ( 4-7 ) 6 ( 4-8 ) 9 ( 4-9 ) x = 4 ( 4-10 ) 6 ( 4-11 ) 9 ( 4-12 ) x = 4 ( 4-13 ) 6 ( 4-14 ) 9 ( 4-15 ) EMVE11 (4-16) EMVE15 (4-17) EMVE21 (4-18) EEVE11 (4-19) EEVE15 (4-20) EEVE21 (4-21)Figure 4-1. Synthesis of EVE copolymers: (i) MeI, NaH, DM F (ii) EtBr, NaH, DMF (iii) SchrockÂ’s catalyst, high vacuum, (iv) Pd(C), H2(1000 psi), toluene Molecular Weight and Structural Analysis Unsaturated ADMET products and EVE c opolymers were analyzed using gel permeation chromatography (GPC), 1H NMR, 13C NMR, and FT-IR to confirm reaction conversions and monitor structural purity thr oughout the synthesis. Characterization data for the EVE copolymer family is listed in Table 4-2. Table 4-2 . Characterization data for sequenced EVE copolymers Comonomer (mol%) Unsaturated EVE Copolymersc, d Saturated EVE Copolymersa, d Copolymer Namea Branch Frequencyb Vinyl Ether Ethylene Mw Mn PDIe Mw Mn PDIe EMVE11 (4-16) 14.9 8.3 1.8 15.3 10.0 1.5 EEVE11 (4-19) 11 22 77 24.1 14.6 1.7 25.6 15.7 1.6 EMVE15 (4-17) 39.3 23.1 1.7 41.9 25.2 1.7 EEVE15 (4-20) 15 13 87 48.9 28.1 1.7 43.1 24.6 1.8 EMVE21 (4-18) 81.3 32.0 2.5 74.1 32.7 2.3 EEVE21 (4-21) 21 10 90 9.7 8.5 1.9 11.5 7.3 1.6 a) See Figure 4-1; b) Determined by the number of bac kbone carbons in central repeat unit; c) ADMET products 4-10 through 4-15 ; d) molecular weight (kg/mol) determined by GPC performed in THF relative to polystyrene standards; e) Polydispersity index ( Mw/Mn).

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87 13C and 1H NMR Analysis Polyolefin analysis via 13C NMR spectroscopy has greatly enhanced the characterization of copolymer microstruc ture allowing resolution of endgroups and specific branching patterns in sequenced materials71, 130 and random copolymers.131, 132 The resolution of specific C-C and C-H bonding patterns via 13C NMR allows delineation of detailed aliphatic polymer mi crostructure where FT-IR and 1H NMR analysis can often be vague due to overlapping absorbances or resonances. Spectral data from the EVE copolymers de monstrates the ability of metathesis chemistry to produce linear, sequenced copolym ers as shown in Figure 4-1. Figure 4-2 displays the evolution of 13C NMR spectral data from diene monomer 4-4 to EMVE11 ( 4-16 ), chosen for the high concentration of functional groups, alt hough the interpretation is similar for all reported EMVE materials. Starting at the top, monomer identity is confirmed by signals corresponding to term inal olefin (114.5 and 139.2 ppm), ether carbons (56.6 and 81.1 ppm), and various alky l signals (25-35 ppm). Polymerization affords the unsaturated copolymer 4-10 confirmed by recession of the terminal olefin signals from the monomer and emergen ce of two new signals attributed to trans (130.5 ppm, major) and cis (130.0 ppm, minor) 1,2-disubtituted olefins in the polymer backbone. The presence of low intensity si gnals identical to the monomer verifies – olefin end group identity for a ll unsaturated EVE copolymers ( 4-10 through 4-15 ). After saturation with hydrogen, the bottom spectrum for EMVE11 suggests the successful preparation of the target molecu le by absence of a ll allylic and olefinic signals along with the simplification of the alkyl region revealing the symmetri c nature of the copolymer.

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88 . Figure 4-2. 13C NMR progression fro m monomer to target EVE copolymer

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89 At a molecular weight of over 14 kg/mol, EMVE11 exhibits only five unique 13C NMR signals (A-E, Figure 4-2) due to an axis of symmetry between the and carbons creating degenerate relaxati on times for most carbons in the material and greatly simplifying the spectral data. Carbons A a nd B correspond to the methyl (56.6 ppm) and methine (81.2 ppm) carbons in the ether, and importantly, remain intact throughout the synthesis of EMVE11 . Signals marked C and D represent and carbons to the branch point, respectively, that exist in higher molar concentration than A and B as indicated by greater signal intensity. The final resonance E at 30 ppm corresponds to the remaining six methylenes in the polymer backbone fu rthest from the alkoxy branches as one broadened composite resonance exhibiting multi ple maxima. Methylene signal overlap is compounded for longer run length copolymers like EMVE15 and EMVE21 where higher methylene concentrations lead to a grea ter intensity signal near 30ppm relative to branch point and ether carbons. Analysis of EEVE 13C NMR data follows a similar rati onale as structural analysis presented above and also reveals the single structural difference between the two EVE copolymer families, the alkyl ether substitution. A downfield shift of the primary ether carbon to 64.3 ppm and a signal at 15.9 ppm verify the presence of ethoxy substitution unlike the single resonance displayed by the EMVE series at 56.6 ppm. Otherwise, minor chemical shifts of 0.2 ppm result in some cases, but overlap of extended methylene signals occurs in EEVE materials near 30 ppm, as expected. This overlap represents one limitation of 13C NMR analysis where determination of ethylene run length is difficult, but quantitative 1H NMR analysis allows calculation of molar concentration of methylene units in the material.

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90 1H NMR was performed on all synthesized ma terials for basic structural analysis and verification of comonomer ratios for all EVE copolymers. Determination of comonomer ratios is possible by comparison of downfield integral ratios from ether protons with integral values from over lapping methine, methylene, and methyl resonances, but specific polyol efin bonding patterns are diffi cult to resolv e without the compilation of structural analysis data from multiple analytical techniques. FT-IR Analysis Compound structure and purity was c onfirmed throughout EVE copolymer synthesis using FT-IR spectroscopy. Metathes is polymerizations were verified by the coalescence of two absorbance bands from –olefins in monomers at 991 cm-1 and 908 cm-1 into a single band at 967 cm-1 indicating a mostly trans 1,2-disubstituted olefin and successful polymerizations.6 Figure 4-3 displays FT-IR absorbance traces for EMVE15 , EEVE15 , and unsaturated copolymer 4-20 , all possessing equimola r ether incorporation allowing direct structural comparison of the tw o families of alkyl vinyl ether copolymers. Nevertheless, identical analysis follows for all sequenced EVE materials in this report with minor changes in relative peak intens ity due to varying comonomer ratios. The bottom traces in Figure 4-3 track the hydrogenation of the unsaturated ADMET polymer to copolymer EEVE15 through the elimination of the olefinic band at 967cm-1. Also observed in 1H and 13C NMR analysis, FT-IR spectral data confirms quantitative saturation of metathesis products within experimental error yielding target EVE copolymers. Structural differences between EMVE15 and EEVE15 are easily discernable upon juxtaposition of the IR data in the top two absorbance traces in Figure 2. Strong absorbance bands present at 2926 and 2854 cm-1 for both copolymers correspond to the asymmetric and symmetric methylen e C-H stretching motions from backbone

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91 carbons. For EEVE15 , an absorbance maxima at 2972 cm-1 is also observed corresponding to the methyl C-H stretch of th e pendant ethyl ether branch, unique to the EEVE materials in this study. Th is absorbance is not observed for EMVE15 due to the shift of the methyl ether C-H stretching bands to 2850cm-1, overlapping with the backbone methylene vibrations previously mentioned. 30002500200015001000 30002500200015001000 0 1 30002500200015001000 n O CH3 n O CH2CH3 n O CH2CH3 EEVE15 Copolymer 10 EMVE15AbsorbanceWavenumber (cm-1) Figure 4-3. FT-IR analysis of EVE copolymers Moving to lower wavenumbers, aliphatic me thyl and methylene C-H vibrations are observed for both copolymers. EMVE15 and EEVE15 both display similar scissoring bands at 1466 cm-1 due to identical copolymer backbone s and ethylene sequence lengths. EEVE15 exhibits two specific absorbances ar ising from multiple methylene bonding

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92 arrangements in the polymer backbone and the pendant ethyl et her group leading to bands at 1371 cm-1 and 1344 cm-1, respectively, whereas EMVE15 exhibits only one lower intensity band at 1369 cm-1 once again due to overlap of methyl ether and methylene stretching bands. Analysis of the ether C-O-C stretching at lower wavenumbers allows direct comparison of alkyl substitution patterns from carbon-oxygen bonding rather than indirect an alysis via secondary effects on C-H aliphatic vibrations described above. A single asymmetric ether stretch can be observed in EMVE15 at 1097cm-1 arising from the methyl-isopropyl et her bonding arrangement, while the ethylisopropyl ether arrangement in EMVE15 results in vibronic coupling within the copolymer and a split in the absorb ance to wavenumbers of 1088 and 1112 cm-1. Verification of sequenced c opolymer structures through FT -IR data supports NMR and GPC observations indicating suc cessful synthesis of stric tly linear polyethylene with controlled incorporati on of two different alkyl vinyl ethers. Thermal Analysis Thermal analysis of the ethylene copo lymers has demonstrated the general correlation of increased branch content to decreased melting points and heats of fusion for this diverse family of macromolecules. Notably, sharp melting profiles exhibited by high-density polyethylene become broad transitions in random –olefin copolymers with increasing levels of th e comonomers propylene,133, 134 vinyl chloride,135 and acrylic acid136 due to variable lamellar thickness induc ed by a distribution of ethylene sequence lengths until substitution renders copoly mer amorphous. Thermal analysis of random EVE materials reported in Table 1 either was not performed or not di sclosed in the patent literature.118-126

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93 Thermal analysis of the family of EVE copolymers was performed by differential scanning calorimetry. DSC thermograms fr om second heating and cooling scans at 10C/min and peak melting temperatures and heat s of fusion values for the series of EVE sequenced copolymers are displayed in Figure 44 and data is compiled in Table 4-3. Table 4-3. Thermal analysis da ta for sequenced EVE copolymers Comonomer (mol%) Observed Thermal Transitions (10 C/min) Copolymer Namea Branch Frequency b Vinyl Ether Ethylene Tm ( C) Hm (J/g) Tg ( C) Cp (J/g C) EMVE11 (16) -40 35 -62 0.6 EEVE11 (19) 11 22 77 -4 d 33d -65 0.8 EMVE15 (17) -10 62 EEVE15 (20) 15 13 87 -22 36 EMVE21 (18) 40 78 EEVE21 (21) 21 10 90 28 79 a) See Scheme 1, 4-16 through 4-21 b) Determined by the number of backbone carbons in central repeat unit c) measured at midpoint of transition d) values from annealed sample ( EEVE11 *, Figure 3-4), no melt observed in dynamic scanning Every example in the family of EVE materials exhibits semicrystallinity regardless of the high levels of ether incorporation in to the copolymer. For the EMVE copolymers, melting temperatures ranging from -38C to 40C and heats of fusion from 35 to 78 J/g suggest a similar relationship between comonomer content and thermal response as random ethylene copolymers, but lower heat of fusion values may indicate lower overall crystallinity relative to –olefin copolymers assuming simila r crystal forms. As ethylene sequence length decreases and branch density increases, polymer crystallization is inhibited by both conformational disorder and the presence of short ethylene run lengths which are less likely to crystallize into chai n folded lamellae, resulting in low melting copolymers.71

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94 Figure 4-4. DSC second hea ting and cooling scans for six sequenced EVE copolymers and an one heating scan labeled EEVE11 * annealed at -25C and quenchcooled prior to analysis EEVE copolymers display the same melting point trend as EMVE materials with systematically lower melting point values for ethoxy polymers relative the methoxy materials with only one exception. Interestingly, EEVE21 melts at 28C with a heat of fusion of 80 J/g and EEVE15 melts at -33C with a heat of fusion of 35 J/g roughly 12 degrees lower than their EMVE analogs, but EEVE11 breaks this trend displaying a cold crystallization not observed with an y other copolymer in this study. EEVE11 displays an initial relaxation at -65C, followed by a cold crystallization peak at-34C, and crystal melting at -6C. Evidence of a glass transition te mperature and no recr ystallization is

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95 observed during cooling unlike other copolym ers that all reveal uniform melting and recrystallization profiles under dynamic scanning conditions but do not exhibit glass transition temperatures. The lack of EEVE11 crystallization during cooling at 10C/min may arise from steric conges tion of ethoxy branches and kine tic factors, but observation of polymer crystall ization is possible upon annealing at -25C for one hour followed by quench cooling. Upon heating the annealed sample, a melting profile indicating polymer crystallization can be observed w ith a peak melting temperature of -4C, surprisingly higher than EMVE11 at -40C and comparable to EMVE15 at -9C. The heat of fusion of 33 J/g for EEVE11 also deviates from this tren d yielding little difference from EEVE15 at 36 J/g and EMVE11 at 35 J/g. In this sense, the thermal behavior of EEVE11 is not well understood in this study or upon comparison with previously synthesized sequenced materials,6, 71 and these results may indicate a different crystal structure for EEVE11 compared to the other five EVE materials Glass transition temperatures for the EV E copolymers were only observed for the two most highly functio nalized copolymers, EMVE11 and EEVE11 , with a midpoint value at -65C. Figure 4-4 illustrates all thermal responses observed when scanning from -150 to 140C although data has been clipped to hi ghlight melting endotherms. The lack of observation of this relaxation in ot her EVE copolymers is likely due to the semicrystalline nature of the materials known to inhibit resolution of thermal relaxation in DSC analysis. Conclusion A family of six sequenced copolymers of ethylene with both met hyl and ethyl vinyl ether have been prepared at targeted co monomer ratios creati ng materials possessing

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96 exact ethylene run lengths betw een pendant ether branches. To our knowledge, this is the first report of the structur e-property relationship for st rictly linear EVE copolymers exhibiting no branching defects. Spectrosco pic analysis via NMR and FT-IR reveals the microstructural control available via metathesis polymerization indicating no detectable side reactions during polymeri zation or hydrogenation. The pr istine nature of isolated copolymer structures has marked effects on thermal behavior, a nd all sequenced EVE copolymers exhibit semicrystalline morphologi es with peak melting temperatures and heats of fusion proportional to comonomer ratio in all but one case where an ethoxy substituted copolymer underwen t cold crystallization to an unexpectedly high peak melting point. Although the homogeneous di stribution of alkoxy functional groups throughout the EVE copolymers should seemi ngly maximize conformation disorder in the material, the ability to retain sequence le ngth control and a high degree of structural regularity permits copolymer crystallization giving peak melting points between -40 and 40C for the family of EVE materi als. Although one copolymer, EEVE11 , fails to correlate the trend of increasing ethylene run lengths to higher peak melting points, we believe the level of ether incorporation and the size of the ethoxy pendant group may possibly induce different chain packing and alte r the crystal structure in this material relative to the other EVE copolymers in the study.

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97 CHAPTER 5 SEQUENCED COPOLYMERS OF ETHYLENE AND PROPYLENE: THE EFFECTS OF SHORT ETHYLENE RUN LENGTHS Introduction Sixty years of research pe rtaining to polyolefin struct ure and crystallization has created volumes of data regarding the e ffect of polymer branching on material properties.137-140 Although pendant alkyl branches, such as methyl groups, have been shown to reside both within polymeric crys tals and throughout th e amorphous regions of bulk materials,72, 141-144 both radical initiated and chain growth polymerizations lead to creation of irregular methylene sequence leng ths between branches, thereby, reducing the propensity for polyolefin crystallization. Due to variable lengths of uninterrupted, easily crystallizable ethylene sequen ces in the material, semicrys talline polyolefins exhibit a distribution of lamellar crys tal thicknesses, pr oducing complex morphologies and broad melting behaviors.133, 143-146 Examples of linear ethyl ene-propylene (EP) copolymers illustrate this point well, as methyl branch ing in these materials has produced a large variety of bulk manifestations – in the realm of brittle solids to adhesive liquids, with the final material response dependant on comono mer content, branch distribution, and polymerization mode. Despite th e occurrence of chain-transfer side reactions that lead to imperfect microstructure,75 the versatility of polyolefi n production is clear as freeradical,147, 148 Ziegler-Natta,107, 133, 134, 149-152 metallocene,146, 153-157 and/or late transition metal157-160 polymerizations are used to target specific branching defects and elicit a wider range of poten tial applications.137, 140 For proper investigation of the structure-

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98 property relationship in polyolefin s and to further clarify the role of alkyl branching in these materials, the synthesis of macromolecu lar architectures with precise control over both branch identity and distribution is necessary. Recently, a family of sequenced EP copolym ers with exact chemical repeat units were synthesized through a metathesis polymerization/hydrogenation approach.6, 7 First, acyclic diene metathesis (ADMET) produces an unsaturated copolymer with absolute control over alkyl branch identity and frequency along the polymer backbone;61, 62, 65 subsequently, exhaustive hydrogenation of this material yields sequenced ethylene-olefin copolymer analogs unatta inable through standard chain copolymerization techniques. Approaching ethylene-olefin copolymer synthesis in this fashion has yielded et hylene-propylene (EP),71, 72, 143 ethylene-1-butene,161 and ethylene-1-octene162 materials exhibiting pristine microstructures with exact ethylene sequence length between branch es. We now report the exte nsion of our EP copolymer work and a new synthetic methodology that enables the crea tion of sequenced copolymers with shorter ethylene run lengths and higher methyl branch content. This report details the synthesis of two highly branched, yet sequenced, ethylene-propylene copolymers and the effects these short ethylene run lengths have on the spectroscopic and thermal behavior of these materials. The EP copolymers described herein possess methyl branches that are ev enly spaced along the PE backbone at every 5th or 7th carbon yielding a controlled number of 4 or 6 methylene units, respectively, between each branch point. The creation of highly branched EP copolymers by ADMET chemistry required an alternate synthetic appr oach where diene monomers were produced bearing two distinct methyl branch points. This methodology not onl y allows for creation

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99 of the sequenced EP copolymers presented he re but also provides a technique for the preparation of highly branched polyethylenes or f unctionalized materials with a thermally stable hydrocarbon backbone. Extensive structur al and thermal characterization was used to examine the impact that short ethylene r un lengths have on the materials response for this of EP copolymers. Experimental Section Materials All materials were purchased from Aldric h and used as received unless otherwise specified. SchrockÂ’s molybdenum catalyst [(CF3)2CH3CO]2(N-2,6-C6H3i Pr2)Mo=CHC(CH3)2Ph was synthesized according to literature procedures.128 Sodium hydride was 60% in mineral oil to facilitate weighing and limit fire hazard. Unless otherwise stated, reactions were performe d in flame dried glassware under argon in tetrahydrofuran (THF) obtained from a nitroge n pressurized Aldrich keg system with an inline activated alumina drying column. Instrumentation and Analysis All 1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were recorded on a Varian Associates Mercury 300 spec trometer. Chemical shifts for 1H and 13C NMR were referenced to residual signals from CDCl3 (1H = 7.27 ppm and 13C = 77.23 ppm) with 0.03% v/v TMS as an internal reference. Thin layer chromatography (TLC) was performed on EMD silica gel coated (250 m thickness) glass plates. Developed TLC plates were stained with i odine absorbed on silica to produce a visible signature. Reaction progress and relative purity of crude products were monitored by TLC chromatography and 1H NMR. Fourier transform infrar ed (FT-IR) measurements were conducted on polymer films cast from chlorofo rm onto KBr plates us ing a Bruker Vector

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100 22 Infrared Spectrophotomete r. High-resolution mass spectral (HRMS) data were obtained on a Finnegan 4500 gas chromatograph/mass spectrometer using either the chemical ionization (CI) or elect rospray ionization (ESI) mode. Differential scanning calorimetry (DSC) wa s performed using a Perkin-Elmer DSC 7 equipped with a controlled cooling accessory (CCA-7) at a heating rate of 10 ºC/min unless otherwise stated. Calibrations were made using indium a nd freshly distilled n octane as the standards for peak temperature transitions and indium for the enthalpy standard. All samples were prepared in hermetically sealed pans (4-7 mg/sample) and were run using an empty pan as a referen ce. Thermogravimetric analysis (TGA) was performed on a Perkin-Elmer TGA-7 at 20oC/min under a nitrogen atmosphere. Gel permeation chromatography (GPC) was performed using a Waters Associates GPCV2000 liquid chromatography system with its internal differen tial refractive index detector (DRI) at 40C using two Waters Styragel HR -5E columns (10 microns PD, 7.8 mm ID, 300 mm length) with HPLC grade THF as the mobile phase at a flow rate of 1.0 mL/minute. Injections were made at 0. 05-0.07 % w/v sample concentration using a 220.5 l injection volume. Retention times were calibrated against narrow molecular weight polystyrene standards (P olymer Laboratories; Amherst, MA). All standards were selected to produce Mp or Mw values well beyond the expected polymer's range. Synthesis of EP7 Copolymer OEt EtO O O Diethyl-2-(but-3-enyl) malonate (5-1) 4-bromo-1-butene (20.6 g, 153 mmol) was a dded to a stirred slurry of diethyl malonate (48.8 g, 305 mmol), sodium hydrid e (4.39 g, 183 mmol), and THF (120 mL) at

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101 0C and allowed to stir for 30 minutes. The resultant mixture was heated to 60C for 8 hours. After cooling to room temperature, the reaction was slowly quenched with water (150 mL) and finally concentrated HCl (~10mL) until acidic (pH~4). Column chromatography (1:3 diethyl ether:hexanes) a fforded 25.2 g (77.2% yield) of colorless oil. 1H NMR spectral data matched reported values.163 13C NMR (CDCl3): (ppm) 14.28, 28.05, 31.51, 51.42, 61.51, 116.14, 137.10, 169.63; CI/HRMS: [M+H]+ calcd. for C21H19O4: 215.1283, found: 215.1282. O O OEt EtO OEt EtO O O 1,6-(Diethyl-2-(but-3-enyl)malonyl) hexane (5-2) Compound 5-1 (15.0 g, 70 mmol) was added to a slurry of sodium hydride (1.68 g, 70 mmol) in THF (75 mL) by syringe at 0C. 1,6-Dibromohexane (7.77 g, 32 mmol) was added slowly to the solution via sy ringe and the mixture warmed to 65C for 8 hours. Once cooled to room temperature, the r eaction was subsequently quenched by slow addition of water (100 mL) and HCl (~ 5 mL) until acidic (pH~4). Column chromatography (3:7 ethyl ether:hexanes) afforded 8.4 g (51.7% yield) of colorless oil. 1H NMR (CDCl3): (ppm) 1.09-1.33 (br, 20H), 1.87 (m, 4H), 1.95 (m, 8H), 4.17 (q, 8H), 5.02 (m, 4H), 5.78 (m, 2H); 13C NMR (CDCl3): (ppm) 14.29, 24.13, 28.57, 29.80, 31.69, 32.44, 57.42, 61.21, 115.10, 137.87, 171.86; CI/HRMS: [M+H]+ calcd. for C28H47O8: 511.3276, found: 511.3271; Elemental analysis calcd. for C28H46O8: 65.86 C, 9.08 H; found: 65.66 C, 9.27 H.

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102 O O OH HO OH HO O O 2,9-(But-3-enyl)-2,9-dicar boxysebacic acid (5-3) Potassium hydroxide (25.0 g, 446 mmo l) was added to a mixture of 2 (20.0 g, 39 mmol) in ethanol (125 mL) and water (50 mL ) at room temperature. The reaction mixture was heated at reflux for two hours befo re cooling to room temperature. Diethyl ether (100 mL), followed by water (50 mL) and finally concentrated HCl (~200 mL) were added over thirty minutes until acidic (pH~4). The biphasic mixture was transferred to a separatory funnel, extrac ted twice with diethyl ether (2 x 150 mL), washed with brine (2 x 150mL), and concentrated to a hydrated yellow solid at 118% crude yield of a mixture of tetraacid and what appeared to be potassium chloride. No further purification was performed LSI/HRMS: [M+Na]+ calcd. for C20H30O8Na: 421.1823, found: 421.1836; Elemental analysis calcd. for C20H30O8: 60.29 C, 7.59 H; found: 59.97 C, 7.67 H. O HO OH O 2,9-(But-3-enyl)sebacic acid (5-4) Solid tetraacid 5-3 (24.8 g, 62 mmol) was mixe d with Decalin™ (25 mL) and heated to 185oC in a 250mL round bottom flask equipped with an air cooled condenser connected to a mineral oil bubbler. The reaction was stirred vigorously until gas evolution ceased (typically 30 minutes at this scale). Upon c ooling, Decalin™ was removed via rotary evaporation affording a yellow oil. Column chromatography (100% ethyl acetate) afforded 15.6 g (80.9% yield from 2 ) of yellow oil. 1H NMR (CDCl3): (ppm) 1.20-1.89 (br, 16H), 2.10 (q, 4H), 2.39 (m, 2H), 5.02 (m, 4H), 5.79 (m, 2H), 11.74

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103 (br, 1.5H); 13C NMR (CDCl3): (ppm) 27.33, 29.47, 31.45, 31.68, 32.23, 45.05, 115.43, 137.96, 183.01; LSI/HRMS: [M+Na]+ calcd. for C18H30O4Na: 333.2057, found: 333.2048; Elemental analysis calcd. for C18H30O4: 69.64 C, 9.74 H; found: 68.69 C, 9.71 H. HO OH 2,9-(But-3-enyl)-1,10-decanediol (5-5) A solution of diacid 5-4 (8.7 g, 28 mmol) in THF was added dropwise to a slurry of LAH (10.6 g, 279 mmol) in diethyl ether at 0C. The mixture was warmed to 45C and stirred for 4 hours. The reaction was quenc hed with successive additions of water (50mL) and 6N HCl (300 mL) over thirty minut es. The organic phase was collected in two ether (150mL) washings, washed with brine (2 X150mL), and dried with MgSO4. Filtration and solvent removal afforded an oil with a slight yellow hue. Column chromatography (3:7 hexanes:diet hyl ether) yielded 6.2 g (78.2 % yield) of colorless oil. 1H NMR (CDCl3): (ppm) 1.28-1.58 (br, 20H), 2.08 (q, 4H), 3.55 (d, 4H), 4.98 (m, 4H), 5.82 (m, 2H); 13C NMR (CDCl3): (ppm) 29.97, 30.14, 30.37, 31.01, 31.32, 40.14, 65.60, 114.58, 139.22; CI/HRMS: [M+H]+ calcd. for C18H35O2: 283.2637, found: 283.2633; Elemental analysis calcd. for C18H34O2: 76.54 C, 12.13 H; found: 75.91 C, 12.01 H. CH3 CH3 5,12-Dimethyldodeca-1,15-diene (5-6) A solution of diol 5-5 (3.78 g, 13 mmol) in triethyl amine (5.0 mL, 49 mmol) and chloroform (75 mL) was cooled to 0oC, and mesyl chloride (3 .5 g, 31 mmol) was added

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104 dropwise via syringe over 5 minutes. Th e reaction mixture was warmed to room temperature and stirred for 1 hour. The crude mixture was transferred to a separatory funnel and washed water (2 x 50 mL), 1N HCl (2 x 50 mL), and saturated potassium carbonate (2 x 50 mL). Each washing was extracted with dichloromethane (50 mL). The chloroform and dichloromethane porti ons were combined, dried with MgSO4 and concentrated to an orange oil. A solution of crude dimesylate in diethyl ether (75 mL) was added dropwise, over a twenty minute period, to a slurry of precooled (0C) of LAH (6.0 g, 158 mmol) in diethyl ether (150 mL). The reaction was warmed to room temperature and stirred for 1 hour. Successive additions of water (6 mL), 15% NaOH (6 mL), and water (18 mL) followed by filtration and solvent removal yielded a biphasic, colorless mixture. Column chromatography (100% hexanes) isolated 2.3 g (68.7 % yi eld) of colorless oil. 1H NMR (CDCl3): (ppm) 0.87 (d, 6H), 1.0-1.5 (br, 18H), 2.06 (m, 4H), 4.98 (m, 4H), 5.83 (m, 2H); 13C NMR (CDCl3): (ppm) 19.76, 27.24, 30.25, 31.62, 32.51, 36.48, 37.18, 114.13, 139.69; CI/HRMS: [M]+ calcd. for C18H34: 250.2661, found: 250.2669; Elemental analysis calcd. for C18H34: 86.32 C, 13.68 H; found: 84.49 C, 13.52 H. CH3 CH3 n Polymerization of 5,12-dimethylhe xadeca-1,15-diene: EP7u (5-7) Prior to reaction, pure diene monomer 5-6 was successively vacuum transferred onto a potassium metal mirror; allowed to stan d for 4 hours at room temperature; vacuum transferred to a 50 mL Schlenk flask and ta ken into an Argon filled glove box. Diene monomer 6 (1.0 g) was added to SchrockÂ’s mo lybdenum catalyst (1500:1) and stirred until ethylene evolution slowed and the visc osity increased. The reaction flask was

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105 sealed with a Schlenk adapter, taken out of the glove box, and fitted to a high vacuum line. Vacuum was applied intermittently over three hours during which noticeable viscosity increase of the golden amorphous liquid was observed. High vacuum (~10-4 torr) was applied, and the temperature increased to 40C for 72 h. The polymerization was quenched by opening the flask to the atmo sphere and adding toluene (25 mL). Upon dissolution, polymer solutions were stirred until a green color arose and finally flashed through a 2” plug of neutral silica to rem ove catalyst residue. Removal of solvent afforded a colorless liquid polymer. 1H NMR (CDCl3): (ppm) 0.85 (d, 6H), 1.02-1.45 (br, 18H), 1.99 (m, 4H), 5.33-5.45 (m, 2H); 13C NMR (CDCl3): (ppm) 19.81, 25.02, 27.28, 30.31, 30.41, 32.50, 32.65, 37.23, 37.34, 130.13 ( cis olefin), 130.59 ( trans olefin); FT-IR: (cm-1) 2963, 2925, 2850, 1462, 1376, 967, 722; Elemental analysis calcd. for C17H32: 86.36 C, 13.64 H; found: 86.45 C, 13.79 H. Thermal decomposition under nitrogen @ 10oC/min: 10% weight loss at 417oC. CH3 n EP7 (5-8) Unsaturated polymer 5-7 (~1.0 g) was dissolved in toluene (150 mL) and transferred to a Parr pressure reactor equipped with a glass sleeve and Teflon stirbar. Palladium (10 mol% on carbon) (100 mg) was added to the solution; the reactor was sealed, was purged three times with 1000 psi hy drogen gas, and filled to 1000 psi prior to heating the stirred contents to 120C for 72 h. The crude reaction mixture was vacuum filtered over a 2” plug of silica to remove carbon residue. Subsequent removal of solvent gave 947 mg (95% mass yield from 1g of 5-6 ) of a colorless liquid polymer. 1H NMR (CDCl3): (ppm) 0.85 (d, 3H), 1.02-1.45 (br, 13.67H); 13C NMR (CDCl3): (ppm)

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106 19.98, 27.37, 30.35, 33.01, 37.38; FT-IR: (cm-1) 2924, 2853, 1464, 1377, 723; Elemental analysis calcd. for C17H34: 85.63 C, 14.37 H; found: 85.53 C, 14.66 H. Thermal decomposition under nitrogen @ 10oC/min: 10% weight loss at 315oC. Synthesis of EP5 copolymer Synthetic methodology to produce EP5 is identical to that given previously for the total synthesis of the EP7 copolymer. O O O O OEt EtO OEt EtO 1,4-(diethyl-2-allylmalonyl) butane (5-9) Column chromatography (2:8 ethyl ether:hexanes) produced 9.6 g (58.7% yield.) of a colorless oil. 1H NMR (CDCl3): (ppm) 1.12-1.26 (br, 16H), 1.79 (m, 4H), 2.58 (d, 4H), 4.14 (q, 8H), 5.05 (m, 4H), 5.59 (m, 2H); 13C NMR (CDCl3): (ppm) 14.22, 24.25, 32.07, 37.08, 57.42, 61.24, 118.93, 132.65, 171.33; CI/HRMS: [M+H]+ calcd. for C24H39O8: 454.2678, found: 454.2671; Elemental analysis calcd. for C24H38O8: 63.42 C, 8.43 H; found: 63.30 C, 8.45 H. O O O O OH HO OH HO 2,7-diallyl-2,7-dicarboxysuberic acid (5-10) Product isolated as a hydrated mixture of tetraacid and what appeared to be potassium chloride in 113% crude yield. No further purification was performed. LSI/HRMS: [M+Na]+ calcd. for C28H47O8Na: 365.1212, found: 365.1216; Elemental analysis calcd. for C16H22O8: 56.13 C, 6.48 H; found: 55.97 C, 6.38 H.

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107 O O HO OH 2,7-diallylsuberic acid (5-11) Column chromatography (100% ethyl aceta te) isolated 13.2 g (74.7% yield from 9 ) of yellow oil. 1H NMR (CDCl3): (ppm)1.25-1.43 (br, 4H), 1.45-1.72 (br, 4H), 2.182.31 (m, 2H), 2.32-2.50 (m, 4H), 5.10 (m, 4H), 5.76 (m, 2H); 13C NMR (CDCl3): (ppm) 27.26, 31.37, 36.24, 36.31, 45.33, 117.27, 135.28, 182.55; LSI/HRMS: [M+Na]+ calcd. for C14H22O4Na: 277.1416, found: 277.1410; Elemental analysis calcd. for C14H22O4: 66.12 C, 8.72 H; found: 66.11 C, 8.80 H. HO OH 2,7-diallyl-1,8-octanediol (5-12) Column chromatography (15: 85 hexanes:diethyl ether) yi elded 4.5 g (71.2 %) of a colorless oil. 1H NMR (CDCl3): (ppm) 1.32 (br, 8H), 1.61 (b r, 4H), 2.11 (t, 4H), 3.54 (d, 4H), 5.05 (m, 4H), 5.81 (m, 2H); 13C NMR (CDCl3): (ppm) 27.41, 30.76, 36.00, 36.02, 40.59, 65.73, 116.39, 137.30; LSI/HRMS: [M+H]+ calcd. for C14H27O2: 227.2011, found: 227.2009; Elemental analysis calcd. for C14H26O2: 74.29 C, 11.58 H; found: 74.14 C, 11.57 H. CH3 CH3 4,9-Dimethyldodeca-1,11-diene (5-13) Column chromatography (100% hexanes) yielded 3.3 g (87.4 % yield) of a colorless oil. 1H NMR (CDCl3): (ppm) 0.88 (d, 6H), 1.04-1.55 (br, 10H), 1.91 (m, 2H), 2.05 (m, 2H), 4.99 (m, 4H), 5.79 (m, 2H); 13C NMR (CDCl3): (ppm) 19.68,

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108 27.58, 33.03, 36.84, 41.67, 41.69, 115.58, 138.01; CI/HRMS: [M]+ calcd. for C14H26: 194.2035, found: 194.2025; Elementa l analysis calcd. for C14H26: 86.52 C, 13.48 H; found: 86.34 C, 13.70 H. CH3 CH3 n Polymerization of 4,9-dimethyldodeca-1,11-diene: EP5u (5-14) 1H NMR (CDCl3): (ppm) 0.85 (d, 6H), 1.02-1.52 (br, 10H), 1.84 (m, 2H), 1.98 (m, 2H), 5.36 (m, 2H); 13C NMR (CDCl3): (ppm) 19.76, 27.66, 33.45, 34.92, 35.73, 36.89, 40.41, 40.43, 129.46 (cis olefin), 130.31 (trans olefin); FT-IR: (cm-1) 3004, 2953, 2925, 2855, 2724, 1464, 1438, 1376, 968, 725; Elemental analysis calcd. for repeat unit C13H24: 86.59 C, 13.41 H; found: 86.76 C, 13.38 H. Thermal decomposition under nitrogen @ 10oC/min: 10% weight loss at 375oC. CH3 n EP5 (5-15) Isolated as 984 mg (98% mass yield from 1.0 g of 5-13 ) as a colorless liquid polymer. 1H NMR (CDCl3): (ppm) 0.85 (d, 3H), 1.02-1.43 (br, 9.19H); 13C NMR (CDCl3): (ppm) 19.99, 27.70, 33.03, 37.41; FT-IR: (cm-1) 2952, 2925, 2855, 2722, 1464, 1377, 1152, 727; Elemental analysis calcd. for C13H26: 85.63 C, 14.37 H; found: 85.54 C, 14.60 H. Thermal decomposition under nitrogen @ 10oC/min: 10% weight loss at 275oC.

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109 Results and Discussion Polymer Design and Synthesis Sequenced EP copolymers have been pr oduced using ADMET chemistry affording a family of methyl branched polyethylenes (EP copolymers) with targeted comonomer ratios and precise branch placement.71 To easily describe the sequenced copolymers in this document, the nomenclature is based on the parent chain-addi tion comonomers and branch frequency. For example, EP21 begins with the prefix EP standing for ethylene ( E ) and propylene ( P ), the two comonomers, and the number 21 is the branch frequency along the polymer backbone. EP21 can be considered a linear PE with a methyl branch on every 21st carbon or a sequenced EP copolymer w ith 9.5 units of ethylene between each propylene unit. Synthesis of ADMET EP copolymers began with EP19 in 1997164 followed by an extension of this theme to include EP9, 11, 15, & 21.71, 72, 143 All of the aforementioned ADMET EP copolymers exhibit semicrystal line behavior; and for every copolymer, higher branch frequencies and shorter ethylen e run lengths result in lower peak melting temperatures and heats of fusion.71, 143 Figure 5-1 illustrates a comparison of thermal responses for EP9, EP15, and EP21 that hi ghlights their melting endotherms. Longer ethylene run lengths present in EP15 and EP 21 lead to higher melting, more crystalline materials due their possessing a lower methyl branch (defect) content along the polymer backbone. As branch content increases in these EP copolymers, the ethylene run length decreases, thereby, yielding less crystall ine materials with lower peak melting temperatures; however, due to the precise pl acement of pendant methyl branches, even EP9, having the highest molar concentration of defects, still retains a relatively sharp melting profile. Before this work, our group had yet to synthesize an amorphous

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110 sequenced EP copolymer, even though compar able, randomly (or statistically) branched EP copolymers in the literature exhibit both semi-crystalline133, 165 and/or amorphous behavior.159, 160 By creating polymers with pure microstructures and exact branch placement, we have synthesized a class of EP materials with unique structure and morphology. -40-200204060 30 35 40 45 50 55 Heat Flow, Endo Up (mW)Temperature (oC) CH3 nEP21 CH3 nEP15 CH3 nEP9 Tm = -13oC hm = 39 J/g Tm = 39oC hm = 87 J/g Tm = 63oC hm = 140 J/g scan rate =10oC/min Figure 5-1. DSC thermograms of pr eviously synthesized EP copolymers For highly branched copolymers, the diene monomers for metathesis polymerization were synthesized as ‘dimer s’, in an ADMET sense, containing two methyl branch points per monomer. This is the first report of this synthetic methodology that lends itself well to the future creati on of a variety of highly functionalized ADMET

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111 polymers. Figure 5-2 illustrates the monomer synthesis for diene 5-6 , with an abbreviated route for diene 5-13 . A tetraester substituted , -diene 5-2 is produced by the dialkylation of a dibromid e with the alkenyl malonate 5-1 forming a tetraester diene. Subsequent saponification and decarboxyl ation yields the diacid diene 5-4 that is easily converted to the diol 5-6 through LAH reduction. Dimesylation followed by reductive cleavage with LAH yields diene monomer 5-6 . Monomer 5-13 is produced in a similar fashion starting from alkenyl ma lonate and dibromo butane. OEt EtO O O NaH, THF Br Br O O O O OEt EtO OEt EtO NaOH EtOH/H2O LAH THF CH3 CH3 O O OEt EtO OEt EtO O O OEt EtO O O OEt EtO O O Br NaH, THF NaH, THF Br Br DecalinTM CH3 CH3 O O OH HO OH HO O O O HO OH O HO OH 1. MsCl, pyr 2. LAH, THF (5-1)(5-2) (5-3) (5-4) (5-13) (5-9) (5-6) (5-5) Figure 5-2. ADMET monomer synthesis SchrockÂ’s molybdenum catalyst was c hosen for the ADMET polymerization (Figure 5-3) due to mild metathesis conditi ons and recent reports concerning competitive metathesis/isomerization problems using ruthenium catalysts.166-168

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112 CH3 Schrock's [Mo] catalyst 10-3 torr CH3 1000 psi H2Pd(C), toluene CH3 n CH3 CH3 n EP7u (5-7)EP7 (5-8) (5-6) Figure 5-3 . EP7 copolymer synthesis Upon extensive purification of monomers, the polymeri zation was carried out in the bulk under high vacuum (~10-4 torr). High molecular weight unsaturated copolymers, EP5u and EP7u , were isolated and exha ustive hydrogenation yielded EP5 and EP7 copolymers as colorless viscous liquids. Molecular Weight and Structural Analysis Polymer molecular weight and distributi on were verified by GPC and NMR of both the saturated and unsaturated copolymers. In addition, vinyl polymer endgroups and 1,2disubstituted olefin signals visible in 1H and 13C NMR of the unsaturated polymers vanish upon saturation, indicati ng successful synthesis of saturated EP copolymers. As shown in Table 5-1, retention of both molecular weight and polydispersity upon hydrogenation suggests no polymer degrad ation during hydrogenation, and FT-IR analysis also confirms meta thesis polymerization and copol ymer saturation, yielding the final sequenced EP copolymers. The atactic na ture of the product copolymers arises from the lack of stereocontrol during the initial polymerization of terminal olefins, and a further randomization through transmetathesi s reactions occurring on 1,2-disubstituted olefins along the polymer backbone. Detail ed discussion concerning structural and thermal characterization for copolymers EP5 and EP7 follows.

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113 Table 5-1. Polymer Characterization Data Mol % Ethylene Mol % Propylene GPC datac Calculateda NMRb Calculateda NMRb Mn Mw PDId Onset (oC) of Decompositione Methyl Branch Densityf EP5u 26.0 45.7 1.8 375 EP5 60.0 60.7 40.0 39.3 28.4 47.6 1.7 275 200 (197) EP7u 12.7 20.3 1.6 417 EP7 71.4 72.3 28.6 27.3 12.9 20.3 1.6 315 143 (137) a) calculated from expected polymer repeat unit; b) from 1H NMR analysis; c) kg/mol, referenced to PS standards in THF; d) Mn/Mw; e) recorded at 10% total mass loss under nitrogen gas, 20oC/min; f) calculated from theore tical repeat unit per 1000 Backbone Carbons (1H NMR analysis also included) Structural Analysis: 13C NMR Primary microstructural analysis for these polymers has been greatly enhanced with the application of 1H and 13C NMR techniques. Specifically, the ability of 13C NMR to differentiate similar C-C and C-H bonding arra ngements in hydrocarbon structures such as polyolefins and paraffins produces more structural information than 1H NMR due to similar proton chemical shifts and overlapping resonances.169 Numerous 13C NMR studies of small molecule alkanes have le d to a large collection of spectral data concerning individual branching arrangements for linear molecules and highly branched compounds.169-171 Analogous polymer analysis has been performed to determine branch content,132, 160, 172 branch identity,172 and branch distribution132, 173 in a variety polyolefins. Spectral data for EP5 and EP7 illustrate the structural regularity established in the precisely branched copolymers. Figure 5-4 depicts a side-by-side comparison of the transformations from monomer to unsaturated prepolymer to saturated EP copolymer for both EP5 and EP7 by 13C NMR performed in CDCl3. Starting in the upper left with the terminal diene containing monomer for EP5 , signals at 115.6 and 138.0 ppm vanish when converted to high polymer, while two new signals appear corresponding to the 1,2-

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114 disubstituted double bonds along the polymer backbone as a mixture of trans (130.3 ppm, major) and cis (129.5ppm, minor) olefins. In previous studies, the cis / trans content of typical ADMET materials was found to be approximately 90% trans olefin by long-scan semi-quantitative 13C NMR, a result attributed to the conformation of the most metallocyclobutane intermediate formed duri ng the catalytic cycle of the metathesis polymerization.7 Figure 5-4. 13C NMR analysis following m onomer to copolymer for both EP5 and EP7 Saturation of the ADMET pr oduct greatly simplifies the 13C NMR spectra, and as the signals from all olefinic and allylic carbons are removed, the prec ise microstructure of ppm 0 50 100 ppm 0 50 100 n A BCD E n CH3 CH3 CH3 CH3 CH3 CH3 EP7u EP7 EP7m A B C E DA B C Dterminal olefin terminal olefininternal olefin internal olefinno residual olefin no residual olefin CH3 CH3 n A BCD CH3 CH3 CH3 n CH3 EP5u EP5 EP5m

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115 ADMET EP copolymers becomes apparent. For EP5 , which contains a methyl branch on every 5th carbon, the NMR shows resonan ces from only four magnetically different carbons in a molecule of over 40 kg/mol arising from an axis of symmetry between the and carbons from any branch point in the c opolymer. Since backbone carbons C and D are twice as abundant as the methyl branch (A) and branch point carbons (B), it follows that signal intensity for carbons C and D resemble roughly twice that of carbons A and B. Upon comparison of this spect ral data with previously mentioned NMR studies, our sequenced EP copolymers show good agreement w ith similar small molecules, but slight differences of between 0.5-2 ppm are seen due to the non-repeati ng structure of the latter.169 Comparison of these copolymers to methyl branched polyolefins shows excellent agreement with the bran ch and branch point to <1ppm.172, 174 We postulate these small differences in chemical shift are related to the precise sequence length in our copolymers where the chemical shift of the and carbons are slightly altered by branches on both sides of the carbon atom in question. Analysis of EP7 (Figure 5-4) follows the same appr oach as terminal olefins signals are replaced with those of internal olefins. Once again, the spectrum is greatly simplified after hydrogenation, resulting in only five ma gnetically inequivalent carbons. In this case, the axis of symmetry resides in between the and carbon from any branch point marked as D and E, respectively. As observed with EP5 , the branch point (B) and methyl group (A) are the least populous carbons in the material , resulting in roughly half the signal intensity relative to the other th ree backbone carbons (C, D and E). Again, good agreement with small molecule studies is observed with larger discrepancies for carbon atoms further from the branch point, ar ising from the polymeric nature of these

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116 samples.169 Comparison to similar methyl bran ched polyethylenes reveals superb agreement to reported chemical shifts to within 1 ppm.172, 174 nC H 3 C H 3 A 19.98 D 27.37 I 14.33 G 29.60 H 23.31 E 30.35 F 37.05 C 37.38 B 33.01 ppm 15.0 20.0 25.0 30.0 35.0 A B C D E F G H I Figure 5-5. 13C NMR endgroup analysis of EP7 Endgroup analysis of these c opolymers is also possible by 13C NMR spectroscopy. Previous examination of endgroups pr oduced during ADMET polymerization have shown terminal olefins remain at chain ends,7 and upon hydrogenation, are saturated leaving a unique primary methyl branch175 unlike the secondary me thyl branches along the copolymer backbone of EP5 and EP7 . 13C NMR spectroscopy of EP7 reveals low intensity resonances corr esponding to the polymer endgroups and the neighboring carbons atoms shown as an expanded view (~ 100X) for the alkyl region of the spectrum (Figure 5-5). The large signa ls extending off the top of the spectrum correspond to the backbone carbon atoms with the highest molar concentration in the copolymer, while the four smaller signals labeled G, H, F, and I represent e nd groups and adjacent carbon atoms as labeled. These signals are easily distinguishable and assignment as endgroups

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117 agrees with our analysis of random ADMET EP materials175 and small molecule studies mentioned earlier.169 Endgroup analysis illu strates the power of 13C NMR in polyolefin structure determination and supports th e proposed copolymer structure for both EP5 and EP7 . Structural Analysis: 1H NMR Proton NMR analysis also illustrates the microstructural control offered by the metathesis/hydrogenation methodology. Figur e 5-6 presents a set of proton spectra tracking the conversion of diene monomer 6 to unsaturated copolymer EP7u to saturated copolymer EP7 , similar to the 13C NMR data presented earlier. The spectral data shows the progression from the monosubstituted, term inal olefin of the monomer to the 1,2disubstituted olefin to the satu rated copolymer. The presence of cis and trans olefins in the copolymer are confirmed by the large signal at 5.39 ppm ( trans ) with a small shouldering signal just upfield with a maximum at 5.34 ppm ( cis ). As observed with 13C NMR, analysis of the 1H NMR spectrum for EP7 is straightforward as only three different bonding arrangements for hydrogen exist in the copolymer: a methine, a methylene, and a methyl group. Since 1H NMR can resolve the methyl group signals from the overlapping methine and methylene signals, copolymer branch content and comonomer ratios can be calculated (Table 5-1), but specific bonding arrangements are difficult to deduce. As with 13C NMR, 1H NMR analysis for EP5 and EP7 supports the structural claims and proposed repeat uni ts for both sequenced EP copolymers.

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118 Figure 5-6. 1H NMR analysis following monomer 5-6 to EP7 sequenced ethylenepropylene copolymer Structural Analysis: FT-IR Structural analysis of the EP copolymers using FT-IR is a relatively straightforward analytical technique that can reveal various structural and morphologi cal features of these materials, including crystal st ructure and branching content.176, 177 Previous FT-IR studies on linear paraffins and various grad es of commercial PE have determined the small effects crystallization and chain-packing have on absorbance wavenumber and intensity. In most cases, es pecially in purely hydrocarbon sy stems, what may appear to ppm 0.0 1.0 2.0 3.0 4.0 5.0 6.0 terminal olefininternal olefin n n CH3 CH3 CH3 CH3 CH3 EP7u EP7no residual olefin

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119 be single absorbances arise from composite in teractions of various methyl, methylene, and methine moieties dispersed throughout th e crystalline and amorphous regions in the material.176 While peak maxima and wavenumber ma y be correlated to crystal structure, or lack thereof, our EP5 and EP7 copolymers display absorbances from disordered morphologies associated with am orphous polymers (Figure 5-7). 500 1000 1500 2000 2500 3000 3500 Wavenumbera) EP5 b) EP7 Figure 5-7. FT-IR analysis fo r sequenced EP copolymers; a) EP5 , b) EP7 FT-IR analysis of both unsaturated a nd saturated EP copolymers verifies polymerization to high molecular weight and exhaustive hydro genation of ADMET products yielding copolymers EP5 and EP7 . Observable in both spectra are multiple absorbance bands between 3000 and 2800 cm-1 arising from the abundance of methyl and methylene units in the polymer backbone. Strong bands at 2925 and 2855 cm-1 correspond to the methylene stretching motions from backbone carbons. For EP5 , the shouldering peak at 2952 cm-1, associated with a methyl stretch, exhibits a higher intensity than that of EP7 due to the higher concentra tion of methyl branches in EP5 . C H 3 n n C H 3

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120 For the bands at 1464 and 1377 cm-1, both copolymers show the exact same absorbance maxima corresponding to methylene and me thyl bending located within a highly disordered environment;176 and the higher methyl content in EP5 is reflected as a greater intensity for the spectral bands at 1464 and 1377cm-1 relative to methylene absorbances between 2850 and 2950 cm-1. The low wavenumber band centered near 725 cm-1 for both copolymers corresponds to methylene rocking specifically located wi thin an amorphous phase.176 Thermal Analysis: DSC EP5 and EP7 represent the first ever fully amorphous, sequenced copolymers produced in this fashion. Extensive ther mal analysis has been performed on various academic and commercial PE materials, there by, creating a large vol ume of data on the subject that spans many decades. Very few reviews regarding this topic have been published in the literature,91, 139, 178 and summarizing the extensive thermal data can be difficult due to both the shear num ber of articles as well as th e assortment of conclusions provided therein. Herein, we have cited articles with thermal analysis of random EP copolymers of similar comonomer contents as EP5 and EP7 focusing on structural variations throughout various chain addition methods. The relationship between branch content a nd thermal response of polymers is well documented in the literature, and thermal analys is data for various polyolefins is widely avaiable.137, 140, 179 As a general rule, as short alkyl branching increases, peak melting temperatures and heats of fusion decr ease until branching defects render ethylene-olefin copolymers amorphous , usually above 60 mol% -olefin content.133, 178, 180 For randomly copolymerized EP materials, composition charts have been developed compiling glass transition and peak melting temperatures for semicrystalline and

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121 amorphous EP copolymers based solely on comonomer ratios,144, 157 and predictions of minimum methylene sequences needed for crystallization have been reported as n = 8,181 10,182 and 14.107 Below this critical chain length for polymer crystallization, short methylene sequences have been linked to a low temperature relaxation where T < Tg: n = 2,183 3,184 and 2178 for T = -125oC. While the true glass transition temperature of PE has been debated due to multiple detectable polymer relaxations,178 random EP materials exhibit composite thermal responses fr om PE-like and polypropylene-like polymer segments throughout the material,107, 144, 150 making it difficult to di scern which structural features are causing specific thermal events . The synthetic methodology applied creates macromolecular architectures with defined re peat units generating perfectly sequenced EP materials that offer the abil ity to directly probe the eff ects of specific branch (defect) placement on polymer morphology and crystal structure. Differential scanning calorimetry (DSC) wa s performed on a series of sequenced ADMET EP copolymers to determine the effects of exact ethylene run lengths on thermal response. All previously s ynthesized examples of ADMET EP copolymers (EP9, 11, 15, 19, and 21)71, 72, 143 exhibit semicrystalline behavior with a common trend of increasing peak melt temperature and heat of fusion with increasing ethy lene run length or decreasing branch content (Figure 5-1). A lthough this data is in good agreement with thermal data from the corresponding random ly branched EP materials, ADMET EP copolymers display sharp, well-defined melting endotherms unlike statistical EP copolymers which usually exhibit long, broad melting endotherms due to a the latter having a distribution of ethylene sequ ence lengths and polydisperse lamellae thicknesses.107 Sequenced EP copolymers having ex act ethylene run lengths lead to a

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122 regular repeating polymer structure allowi ng more uniform crystallite formation and lamellar thickness distribution. The glass transition temperatures for all semicrystalline ADMET EP sequenced copol ymers have been recorded at -43oC for ethylene run lengths of n = 8-20 regardless of branch density.71 -120-100-80-60-40-2002040 20 25 30 35 40 45 50 Heat Flow, Endo Up (mW)Temperature (oC) CH3 n CH3 n Tg = -65 oC Cp = 0.5 J/g-oCscan rate = 10oC/min EP5 EP7 Figure 5-8. DSC analysis: seconding heating scan of EP5 and EP7 DSC experiments on EP5 and EP7 were performed at a scan rate of 10oC/min from -120 to 150oC and the second heating curves for the two new additions to this family of EP materials are displayed in Figure 5-8. For EP5 , a single, clearly defined relaxation can be observed at -65oC with a Cp of 0.5 J/g-oC. This transition has been assigned as the glass transition temperature fo r this copolymer, and is roughly 22oC lower than previous examples of sequenced EP copolymers.71 In comparison with literature data for

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123 random EP copolymers, a number of examples exhibit thermal rela xations near this temperature and have been assigned as glass transitions.107, 133, 134, 150, 151, 157, 185 The shift of this relaxation of EP5 to a lower temperature relative to previous perfectly sequenced EP copolymers71, 130, 164 is attributed to a higher methyl branch density inhibiting polymer chain flexibility as seen in ex amples random EP materials also;157 EP5 represents the first example of a completely amorphous, seque nced EP copolymer within this family of precisely branched materials. In other words, we have isolated the branch content necessary to block cr ystallization in a sequenced EP material, or in other words, determined the smallest crystalli zable ethylene run length at 6 carbons. For EP7 , the second heating curve of the experiment at 10oC/min illustrates the long, broad endothermic response occurring over a large temperature range of 120oC (Figure 5-8). This observation was attributed to an initial polymer relaxation at -110oC followed by a secondary relaxation at -80oC overlapping with a possible broad melting event. Concurrent and/or consecutive relaxations and polymer melts are common in highly branched EP materials and are illustrated well by Ferrari,133 Reynaers,134 and Sozzani.152 One notable difference in the thermal response of our sequenced EP7 copolymer is the init ial relaxation at -110oC being close to the reported T transition at -125±10oC.178 While this relaxation has been attr ibuted to long, pendant alkyl branch motion, we observe similar lo w-temperature relaxations in a copolymer with a methylene sequence of six carbons and onl y methyl branches. Unlike previous examples of randomly copolymerized EP materi als of roughly 70 mol % ethylene,107, 134, 157 the initial relaxation for EP7 at -110oC occurred roughly twenty degr ees lower than the reported range of -60oC to -40oC. Since previous examples of methyl branched ADMET EP

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124 copolymers only displayed transitions at -43oC, corresponding to the -glass transition, this lead us to believe we could discount the methyl branches for this low temperature relaxation, but specific litera ture data suggests this -110oC transition arises from methyl branch rotation.186 Considering the relaxation data from EP5 exhibits no such transition, we can relate the methylene sequence of n = 6, corresponding to thr ee sequential ethylene units, to the -110oC and -80oC relaxations, and a few examples from statistical EP systems support this conclusion.150, 178 To further resolve the thermal response of EP7 , various one hour annealing treatments between -72 and -40oC were performed to isolate specific transitions. Using a DSC, the material was held isotherma lly for one hour, rapidly cooled to -120oC, and heated from -120oC to 50oC at a scan rate of 10oC/min. The thermal responses of EP7 upon thermal treatments at various temperatures are given in Figure 59. After annealing EP7 at -72oC, two endotherms appear at -60oC (major) and -30oC (minor) with peak shapes suggesting the melting of polymeric cr ystals rather than chain relaxations, but notably, two different polymorphs due to multiple transitions. Annealing at -65oC shifts the lower temperature peak to -54oC while the second peak is slightly expanded and broadened. The trend conti nues when annealed at -63oC as the first peak recedes slightly and the second increases in peak area. Also, a noted exotherm between the two endothermic transitions suggests a melti ng-recrystallization event, dynamically reordering the polymer chains into a higher melting crystal form during the experiment. At higher temperatur es of -50 and -55oC, the two endotherms merge into a bimodal response centered near -40oC. Annealing at -45oC shows the reappearance of both lower temperature endotherms near -80oC and -60oC, although the bimodal me lt still prevails as

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125 the strongest transition at -30oC. In the final experiment, EP7 was held annealed at -40oC, but the sample exhibited an identical th ermal response to that of the initial DSC experiment (Figure 5-8) under dynamic sca nning conditions and no previous annealing performed. The bimodal melting after assort ed thermal annealing treatments, along with broad thermal response under dynamic scanni ng, supports the hypothesis that the high methyl branch density in EP7 forces the material into a metastable state where chain packing is encumbered thus generating conf ormationally disordered and highly strained crystalline domains. 5 10 15 20 Annealing TemperatureHeat Flow, Endo Up (mW)Temperature (oC) -450C -550C -80-60-40-20020 -500C -630C -650C -720C Figure 5-9. DSC curves for annealing experiments on EP7 Crystal structure analysis of EP21 and EP15 using x-ray powder diffraction data was recently reported indicating a mixed hexagonal-triclinic crystal arrangement in EP15 and EP21 copolymers.72 Due to the regularity of the c opolymer structures and the ability of longer ethylene run lengths to crystallize, secondary structure ch aracterization suggests

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126 that the chain stems nucleate to form staggere d, triclinic arrangements that are able to include methyl branches within the la mellae, while simultaneously providing a mechanism for backbone methylenes to order via a hexagonal sublattice. Drawing from these results, we believe si milar events are taking place during low temperature EP7 melt crystallization. However, ow ing to the higher degree of branch content of EP7, several ill-defined thermal transitions were encountered that indicate that the various crystal forms are both less dense and less stable when compared to the EP15 and EP21 materials desc ribed by Lisa, et al..72 According to our earlier analysis, as ethylene sequence length is decreased, conformational disorder in ADMET EP copolymers is increased leading to lowe r density copolymers with less hexagonal character and more defective triclinic arrangements. Revi siting previously discussed thermal analysis (Figur e 5-1), the response of EP7 seems intuitive as EP5 is completely amorphous and EP9 is a very low-density semicrystalline polymer. The intermediate branch density in EP7 impedes crystallite formation unless specific thermal treatments are applied thus supporting formation of va rious thermodynamically metastable states that cannot be observed under dynamic scanning. For a copolymer containing a run length of shorter than four methylene groups between methyl branches, the only observed transition for EP5 is a clearly defined Tg at -65oC and a Cp of 0.5 J/g, with no melting event detected even upon annealing at various low temperatures. If EP5 has too many branches to crystallize and EP9 has the lowest peak melting temperature of the family, the behavior of EP7 can be explained by branch content alone. At this propylene c ontent, sequenced materi als contain an even distribution of methyl def ects throughout the copolymer backbone, thereby, requiring a

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127 methylene sequence of 7 or more for crysta llization to occur. The development of multiple endotherms and bimodal melting for EP7 can likely be attributed to various low-density crystals with p acking arrangements similar to previously analyzed ADMET materials. Hence, EP7 seems to fall on the boundary of crystalline and amorphous polymers in our family of sequenced EP copol ymers; this indicates that the smallest crystallizable run length between branches is between n = 5 and 8 methylene units, similar to previous predictions and reports described earlier. Conclusion In summary, by applying a new synthetic approach to diene monomer synthesis, two sequenced EP copolymers have been synthesized through a sequential ADMET polymerization/hydrogenation methodology. ADMET EP copolymers were analyzed by FT-IR, 1H NMR, and GPC. 13C NMR was used for to perform in-depth structural investigation and endgroup analys is in order to assign exact chemical shifts for specific methyl branching patterns and sequence leng ths in EP copolymers. Methyl branch contents and distributions were controlle d through metathesis polymerization and targeted copolymers were attained in good yield. This approach to EP copolymer synthesis yields precise model polyolefins that are used to isolate explicit structural features in a single material without the problems asso ciated with multiple-branch identities and variable-com onomer distributions observe d in most chain addition materials. Thermal analysis of sequenced EP co polymers revealed the first amorphous example to date, EP5 , exhibiting a glass transi tion temperature of -65oC and a Cp= 0.5 J/g-oC. Both EP5 , with four carbons betw een branch points, and EP7 , with six carbons between branch points, exhibit amorphous ch aracter under dynamic scanning calorimetry

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128 at 10oC/min; however, annealing experiments carried out at low temperatures for EP7 reveal ill-defined endothermic thermal response s that indicate the pr esence of, disordered, metastable crystalline regimes in this material. Future applications of this synthetic methodology include the investig ation of longer alkyl branch es and longer ethylene sequence lengths in simila r polyolefin copolymers.

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129 APPENDIX 1H AND 13C NUCLEAR MAGNETIC RESONA NCE SPECTRA FOR SELECTED INTERMEDIATES AND TARGET MATERIALS Compounds Described in Chapter 2 2-(4-pentenyl)-6-hepteneoic acid O OH 33 1H NMR (CDCl3): 13C NMR (CDCl3):

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130 2-(7-octenyl)-9-deceneoic acid O OH 66 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 151

131 2-(10-undecenyl)-12-trideceneoic acid O OH 99 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 152

132 2-(4-cyclooctenyl)acetic acid O OH 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 153

133 1-ethoxyethyl-2-(4-pentenyl)-6-hepteneoate O O 33 O 1H NMR (CDCl3): 13C NMR (CDCl3):

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134 1-ethoxyethyl-2-(7-octenyl)-9-decenoate O O 66 O 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 155

135 1-ethoxyethyl-2-(10-undecenyl)-12-trideceneoate O O 99 O 1H NMR (CDCl3): 13C NMR (CDCl3):

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136 1-ethoxyethyl-2-(4-cyclooctenyl)acetate O O O 1H NMR (CDCl3): 13C NMR (CDCl3):

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137 Polymerization of 1-ethoxyethyl -2-(4-pentenyl)-6 -hepteneoate 3 3 n O O O 1H NMR (CDCl3): 13C NMR (CDCl3):

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138 Polymerization of 1-ethoxyethyl-2-(10-undece nyl)-12-tridecenoate 9 9 n O O O 1H NMR (CDCl3): 13C NMR (CDCl3):

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139 EAA9 n OH O 1H NMR (dioxane): 13C NMR (dioxane):

PAGE 160

140 EAA15 OH O 1H NMR (dioxane): 13C NMR (dioxane):

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141 EAA21 OH n O 1H NMR (dioxane): 13C NMR (THF): Figure 2-5

PAGE 162

142 Compounds Described in Chapter 4 1,12-tridecadiene-7-ol OH 4 4 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 163

143 1,16-heptadecadiene-9-ol OH 6 6 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 164

144 1,22-tricosadiene-12-ol OH 9 9 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 165

145 7-methoxy-1,12-tricosadiene OCH3 4 4 1H NMR (CDCl3): 13C NMR (CDCl3): Figure 4-2

PAGE 166

146 9-methoxy-1,16-heptadecadiene OCH3 6 6 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 167

147 12-methoxy-1,22-tricosadiene OCH3 9 9 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 168

148 7-ethoxy-1,12-tridecaadiene OCH2CH3 4 4 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 169

149 9-ethoxy-1,16-heptadecadiene OCH2CH3 6 6 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 170

150 12-ethoxy-1,22-tricosadiene OCH2CH3 9 9 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 171

151 Polymerization of 7-me thoxy-1,12-tridecadiene OMe 4 4 n 1H NMR (CDCl3): 13C NMR (CDCl3): Figure 4-2

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152 Polymerization of 9-meth oxy-1,16-heptadecadiene OMe 6 6 n 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 173

153 Polymerization of 12-methoxy-1,22-tricosadiene OMe 9 9 n 1H NMR (CDCl3): 13C NMR (CDCl3):

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154 Polymerization of 7-ethoxy-1,12-tridecadiene OEt 4 4 n 1H NMR (CDCl3): 13C NMR (CDCl3):

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155 Polymerization of 9-ethoxy-1,16-heptadecadiene OEt 6 6 n 1H NMR (CDCl3): 13C NMR (CDCl3):

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156 Polymerization of 12-ethoxy-1,22-tricosadiene OEt 9 9 n 1H NMR (CDCl3): 13C NMR (CDCl3):

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157 EMVE11 n OMe 1H NMR (CDCl3): 13C NMR (CDCl3): see Figure 4-2

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158 EMVE15 OMe 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 179

159 EMVE21 OMe 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 180

160 EEVE11 n OEt 1H NMR (CDCl3): 13C NMR (CDCl3):

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161 EEVE15 OEt 1H NMR (CDCl3): 13C NMR (CDCl3):

PAGE 182

162 EEVE21 OEt 1H NMR (CDCl3): 13C NMR (CDCl3):

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163 Compounds Described in Chapter 5 Diethyl-2-(but-3-enyl) malonate OEt EtO O O 1H NMR (CDCl3): 13C NMR (CDCl3):

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164 1,6-(Diethyl-2-(but-3-enyl)malonyl) hexane O O OEt EtO OEt EtO O O 13C NMR (CDCl3):

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165 2,9-(But-3-enyl)sebacic acid O HO OH O 1H NMR (CDCl3): 13C NMR(CDCl3):

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166 2,9-(But-3-enyl)-1,10-decanediol HO OH 1H NMR (CDCl3): 13C NMR(CDCl3):

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167 5,12-Dimethyldodeca-1,15-diene CH3 CH3 1H NMR (CDCl3): see Figure 5-6 13C NMR(CDCl3): see Figure 5-4 EP7u from 5,12-Dimethyldodeca-1,15-diene CH3 CH3 n 1H NMR (CDCl3): see Figure 5-6 13C NMR(CDCl3): see Figure 5-4 EP7 CH3 n 1H NMR (CDCl3): see Figure 5-6 13C NMR(CDCl3): see Figure 5-4

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168 1,4-(diethyl-2-allylmalonyl) butane O O HO OH 1H NMR (CDCl3): 13C NMR(CDCl3):

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169 2,7-diallyl-1,8-octanediol HO OH 1H NMR (CDCl3): 13C NMR(CDCl3):

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170 4,9-Dimethyldodeca-1,11-diene CH3 CH3 1H NMR (CDCl3): 13C NMR(CDCl3): see Figure 5-4 EP5u from 4,9-Dimethyldodeca-1,11-diene CH3 CH3 n 1H NMR (CDCl3): 13C NMR(CDCl3): see Figure 5-4

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171 EP5 CH3 n 1H NMR (CDCl3): 13C NMR(CDCl3): see Figure 5-4

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183 BIOGRAPHICAL SKETCH Travis Wayne Baughman, son of Sarah Wh etstone and Gene Baughman, was born in Columbia, SC on April 3, 1979 where he re sided for 18 years. After finishing high school education at Irmo High School in May 1997, Travis enrolled at Clemson University (Clemson, SC) and was accepted into the Textiles, Fiber and Polymer Science program where he completed a B.S. in Te xtile and Polymer Chemistry in May 2001. While at Clemson, coursework under Dr. Mi chael J. Drews and undergraduate research experience under Professors Dennis W. Smith a nd Steve H. Foulger promoted an interest in polymer chemistry and materials design. En couraged by this introduction to scientific research, Travis then enrolled at the Univer sity of Florida (Gainesville, FL) to pursue graduate studies in organic and polymer ch emistry under the advisement of Prof. Ken Wagener in August 2001. Upon completion of Ph.D. requirements in the Spring of 2006, Dr. Travis W. Baughman relo cated to Eindhoven, Netherla nds to begin post-doctoral research under Prof. E. W. Meijer at the Technical University of Eindhoven.