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Decreasing the Alkyl Branch Frequency in Precision Polyethylene

Permanent Link: http://ufdc.ufl.edu/UFE0043587/00001

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Title: Decreasing the Alkyl Branch Frequency in Precision Polyethylene
Physical Description: 1 online resource (155 p.)
Language: english
Creator: Inci, Bora
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: branch -- frequency -- lldpe -- polyethylene -- precision
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Metathesis polycondensation chemistry has been employed to control the crystalline morphology of Linear Low Density Polyethylene (LLDPE) by precisely introducing the alkyl branches along the polymer backbone. These polymers, while structurally akin to copolymers made via chain copolymerization of ethylene and vinyl comonomers, have unique properties, because use of symmetrical a, ? diene monomers ensures precise spacing of the chain branches. An important limitation in this work was the synthesis of the symmetrical diene monomers required in this chemistry. Spacing in the symmetrical monomer directly determines the precision run lengths in the polymer: Prior monomer synthetic schemes have limited the maximum run lengths between branch points along the polymer to 20 methylene carbons (ie, a branch placed on each and every 21st carbon). The present work describes the systematic increase of precision run lengths to 38 and 74 methylene carbons. Successful preparation of symmetrical a,?-dienes for both run lengths is presented. For the case of 38 run lengths, the synthesis and characterization of precisely sequenced polyethylenes containing thirteen different branches allowed systematic examination of the effect of branching on polyethylene properties. A clear change in morphology is observed for these polymers from a situation where the methyl branch is included in the polymer's unit cell, to one where branches of greater mass are excluded from the unit cell. The precision LLDPE model polymers were characterized with Differential Scanning Calorimetry (DSC), Infrared Spectroscopy, Solid State Nuclear Magnetic Resonance Spectroscopy, Wide Angle X-ray Scattering (WAXS) and Transmission Electron Microscopy (TEM). Precision polymer with butyl branches on every 75th carbon was successfully prepared, and X-ray investigation of this polymer displayed an orthorhombic unit cell structure with the absence of metastable phase formation. Increasing the distance between the two consecutive branches from 38 carbons (5.26 mole% branch concentration) to 74 carbons (2.70 mole% branch concentration) fully expels the butyl branches from the crystal lattice to the amorphous phase. This precision polymer with butyl branches on every 75th carbon represents the first realistic model of commercial LLDPE reported so far in precision polyolefin research.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Bora Inci.
Thesis: Thesis (Ph.D.)--University of Florida, 2011.
Local: Adviser: Wagener, Kenneth B.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2013-06-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043587:00001

Permanent Link: http://ufdc.ufl.edu/UFE0043587/00001

Material Information

Title: Decreasing the Alkyl Branch Frequency in Precision Polyethylene
Physical Description: 1 online resource (155 p.)
Language: english
Creator: Inci, Bora
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: branch -- frequency -- lldpe -- polyethylene -- precision
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Metathesis polycondensation chemistry has been employed to control the crystalline morphology of Linear Low Density Polyethylene (LLDPE) by precisely introducing the alkyl branches along the polymer backbone. These polymers, while structurally akin to copolymers made via chain copolymerization of ethylene and vinyl comonomers, have unique properties, because use of symmetrical a, ? diene monomers ensures precise spacing of the chain branches. An important limitation in this work was the synthesis of the symmetrical diene monomers required in this chemistry. Spacing in the symmetrical monomer directly determines the precision run lengths in the polymer: Prior monomer synthetic schemes have limited the maximum run lengths between branch points along the polymer to 20 methylene carbons (ie, a branch placed on each and every 21st carbon). The present work describes the systematic increase of precision run lengths to 38 and 74 methylene carbons. Successful preparation of symmetrical a,?-dienes for both run lengths is presented. For the case of 38 run lengths, the synthesis and characterization of precisely sequenced polyethylenes containing thirteen different branches allowed systematic examination of the effect of branching on polyethylene properties. A clear change in morphology is observed for these polymers from a situation where the methyl branch is included in the polymer's unit cell, to one where branches of greater mass are excluded from the unit cell. The precision LLDPE model polymers were characterized with Differential Scanning Calorimetry (DSC), Infrared Spectroscopy, Solid State Nuclear Magnetic Resonance Spectroscopy, Wide Angle X-ray Scattering (WAXS) and Transmission Electron Microscopy (TEM). Precision polymer with butyl branches on every 75th carbon was successfully prepared, and X-ray investigation of this polymer displayed an orthorhombic unit cell structure with the absence of metastable phase formation. Increasing the distance between the two consecutive branches from 38 carbons (5.26 mole% branch concentration) to 74 carbons (2.70 mole% branch concentration) fully expels the butyl branches from the crystal lattice to the amorphous phase. This precision polymer with butyl branches on every 75th carbon represents the first realistic model of commercial LLDPE reported so far in precision polyolefin research.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Bora Inci.
Thesis: Thesis (Ph.D.)--University of Florida, 2011.
Local: Adviser: Wagener, Kenneth B.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2013-06-30

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043587:00001


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1 DECREASING THE ALKYL BRANCH FREQUENCY IN PRECISION POLYETHYLENE By BORA INCI A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCT OR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2011

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2 2011 Bora Inci

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3 To my p arents

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4 ACKNOWLEDGMENTS I would like to acknowledge my advisor, Professor Ken neth Wagener, for all the guidance and friendship over these many years. His door was always open and whenever I talked with him, I always felt encouraged, with my motivation to work hard revitalized. He has given me a wealth of advice and guidance for things both inside and outside the laboratory. I have never seen him angry, as he always deals with situations in a calm manner. He is a true role model for any graduate student`s professional career. I will forever be thankful for his presence in my life. I would like to thank Professor Fabio Zuluaga for his endless help and guidance especially during my first summer in Gainesville. I had great fun working, drinking, playing soccer, talking politics and singing Venceremos with him. I should also thank to him and Marialena Zuluaga for taking care of me during my visit to Cali, Colombia I want to thank my committee members (Professors John Reynolds, Ronald Castellano, Tony Brennan and Benjamin Smith ) for their time, effort and advice. Furthermore, I want to thank Dr. Kathryn Williams for her helpful discussions and fo r editing my manuscripts. The stay at Florida would not be complete without thanking and acknowledging former and present Wagener group members who made the graduate school a pleasure. I would like to thank Dr. Giovanni Rojas, Dr. Erik Berda Dr. Yuying W ei and especially Dr. James Leonard for their endless help during my first year in the lab. I would like to t hank Brian Aitken and Sam Popwell for their friendship and nice discussions during the last four years. Special thanks to Paula Delgado for her end less help and great friendship. Without her, I could not be able to finish my manuscripts and dissertation. Special thanks to Michael Schulz for reading my dissertation I would like to

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5 thank Ashlyn Dennis for making delicious peach cobbler for me. I want to thank Pascale Attallah and Chip Few for being a great friend. It was a lot of fun sharing my hood with Chip I would like to thank former undergraduate student Adam Garland for his help and friendship. Further, I would like to thank Luke Fischer, Chet S imocco, Donovan Thompson, Nicolas Sauty, Thomas Young and Sotaro Inomata for their friendship. I was very lucky for having opportunity to work in Butler Polymer Research Laboratory. I would like to thank Dr and Mrs. Butler for their support to polymer res earch. Special thanks to Mrs. Sara Klossner, and Mrs. Gena Borrero for their endless help. I think this laboratory is a great place to do research and have fun at the same time. I would like to thank Dr. Dan Patel for his invaluable help, guidance and frie ndship. I had a lot of fun working and discussing science with him. I should thank Dr. Jiango Mei for his guidance and advices. He was extremely helpful during my stay in Gainesville. I would like to thank Laura Moody, Coralie Richard, Stefan Ellinger, Mik e Craig, Romain Stalder, Dr. David Liu, Frank Arroyave and Egle Puodziukynaite for their help and friendship. I would like to thank Alexander Pemba for his endless help and great friendship. As p art of my graduate study, I spent three months in Max Planck Institute for Polymer Research at Mainz, Germany. I would like to thank International Max Planck Research School for Polymer Materials for financial support of this trip. Special thanks to Dr. Ingo Li e berwirth for his endless help and guidance in TEM analy sis during my stay in Mainz. I would like to thank Prof. Dr. Katharina Landfester for making this research experience possible. I also want to thank Dr. Markus Mezger, Dr. Werner Steffen and Michael Bach for their help in WAXS measurements. I would like to thank

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6 Dr. Robert Graf for his help in solid state NMR measurements. Special thanks to Sandra Seywald for her help with GPC measurements. I would like to thank Dr. Robert Haschick and Dr. Katja Niles for taking care of me during my stay in Mainz and for th eir friendship. I also would like to thank Samet Varol for his great friendship and help in Mainz, Germany. team for making the life in Florida enjoyable.

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7 TABLE OF CONTENT S page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 9 LIST OF ABBREVIATIONS ................................ ................................ ........................... 13 ABSTRACT ................................ ................................ ................................ ................... 14 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 16 2 POLYETH YLENE AND CRYSTALLIZATION PHENOMENA ................................ 18 2.1 Historic Importance of Polyethylene ................................ ................................ .. 18 2.2 Discovery of High Density Polyethylene ................................ ........................... 19 2.3 Towards More Specialized Polyethylene ................................ .......................... 23 2.4 Polyethylene Classifications ................................ ................................ ............. 25 2.5 Polyethylene Morphology ................................ ................................ .................. 29 2.5.1 Chain Folding and Lamella Formation ................................ ..................... 29 2.5.2 Unit Cell Structure ................................ ................................ ................... 31 3 ALKYL BRANCHED PRECISION PO LYETYLENE ................................ ................ 34 3.1 Branching in Polyethylenes ................................ ................................ ............... 34 3.1.1 Short Chain Branching ................................ ................................ ............ 34 3.1.2 Long Chain Branchin g ................................ ................................ ............. 37 3.1.3 Quantification of Branching in Polyethylene ................................ ............ 38 3.2 Structure of Precision Branched Polyethylene ................................ .................. 39 3.3 Synthesis and Properties of Precision Branched Polyethylenes ....................... 40 3.3.1 Methyl Branch ................................ ................................ ......................... 41 3.3.2 Ethyl and Hexyl Branches ................................ ................................ ....... 45 3.3.3 Universal Synthesis Route to Symmetrical diene Monomers ........... 47 3.4 Dissertation Purpose ................................ ................................ ......................... 51 4 SYNTHESIS OF PRECISION POLYETHYLENE WITH BRANCHES ON EVERY 39 TH CARBON ................................ ................................ ........................... 53 4.1 Monomer Synthesis ................................ ................................ .......................... 53 4.2 Polymer Synthesis and Primary Structure Characterization ............................. 58 4.3 Primary Structure Characterization of Precisely Branched Polymers ............... 63 4.4 Experimental Section ................................ ................................ ........................ 68 4.4.1 Instrumentation ................................ ................................ ........................ 68 4.4.2 Materials ................................ ................................ ................................ .. 69

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8 4.4.3 Procedures ................................ ................................ .............................. 70 5 CH A RACTERIZATION OF PRECISION POLYETHYLENE WITH BRANCHES ON EVERY 39 TH CARBON ................................ ................................ ..................... 92 5.1 Thermal Behavior of Precisely Branched Polymers ................................ .......... 92 5.2 Determination of Morphology and Crystal Struc ture of Precision Polymers ...... 96 5.2.1 IR Spectroscopy ................................ ................................ ...................... 96 5.2.2 Solid State 13 C NMR ................................ ................................ ................ 98 5.2.3 Wide Angle X ray Diffraction (WAXD) ................................ ................... 101 5.2.4 Trans mission Electron Microscopy (TEM) ................................ ............. 110 5.3 Instrumentation and Sample Preparation ................................ ........................ 114 6 SYNTHESIS AND CH A RACTERIZATION OF PRECISION POLYETHYLENE WITH BRANCHES ON EVERY 75 TH CARBON ................................ .................... 116 6.1 Monomer Synthesis ................................ ................................ ........................ 116 6.2 Polymer Synthesis and Chara cterization ................................ ........................ 122 6.3 Experimental Section ................................ ................................ ...................... 12 7 6.3.1 Instrumentation ................................ ................................ ...................... 127 6.3.2 Materials ................................ ................................ ................................ 129 6.3.3 Procedures ................................ ................................ ............................ 129 SUMMARY AND OUTLOOK ................................ ................................ ....................... 134 APPE N DIX: DSC PROFILES OF PRECISION POLYMERS ................................ ...... 136 LIST OF REFERENCES ................................ ................................ ............................. 143 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 155

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9 LIST OF TABLES Table page 2 1 General properties for various commercial polyethylenes ................................ .. 28 3 1 Effect of precise methyl branch placement on thermal properties ...................... 43 3 2 Effect of precise ethyl branch placement on thermal properties ......................... 46 3 3 Effect of precise hexyl branch placement on thermal properties ........................ 47 3 4 Molecular weights an d thermal data for precision polymers ............................... 49 4 1 Molecular weights and thermal data for precisely branched polymers ............... 63 5 1 Lamellae thicknesses of ADMET PE ................................ ................................ 112 5 2 Unit cell dimensions of HDPE ADMET PE and 4 29a (methyl) ....................... 113 6 1 Effect of copper species on Grignard coupling. ................................ ................ 118 6 2 Molecular weight data for polymers 6 23 and 6 24 ................................ ........... 124 6 3 DSC data for precision polyethylenes possessing butyl branch. ...................... 125

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10 LIST OF FIGURES Figure page 2 1 catalyst. ................................ ................................ ................................ .............. 21 2 2 Mechanism for the Mulheim catalyst u sed in ethylene polymerization. .............. 22 2 3 Location of industrial applic ations of the Mulheim process in the world .............. 23 2 4 Types of polyethylenes ................................ ................................ ....................... 26 2 5 Schematic representation of three phase morpholo gy. ................................ ...... 29 2 6 Transmission electron microscopy bright field image of HDPE single crystal ..... 30 2 7 The observed unit cell structures i n n alkanes and polyethylene ........................ 31 2 8 Polyethylene orthorhombic unit cell with Pnam D 2h space group. ...................... 32 2 9 Metastable polyethylen e unit cells ................................ ................................ ...... 33 3 1 Generally accepted mechanism for the formation of n butyl, n pentyl, n hexyl, 1,3 diethyl and 2 ethylhexyl branches in LDPE. ................................ ................. 35 3 2 Suggested mechanism for sec butyl branch formation ................................ ....... 36 3 3 General chemical structure of precision polyethylene ................................ ........ 39 3 4 General two step synthetic scheme for the preparation of precision branched polyethylene. ................................ ................................ ................................ ...... 40 3 5 Synthesis of methyl branched monomers ................................ ........................... 41 3 6 Synthesis of methyl branched monomers with short ethylene run length ........... 42 3 7 Thermal behavior of polyethylene s ................................ ................................ ..... 44 3 8 S ynthesis of ethyl and hexyl branched monomers. ................................ ............ 45 3 9 diene monomer synthesis. .... 48 3 10 Incorporation of branches from methyl to adamantyl on every 21 st carbon. ....... 48 3 11 Wide angle X ray diffraction patterns for seven precision polymers ................... 50 4 1 General two step synthetic scheme for the preparation of precision branched polyethylene. ................................ ................................ ................................ ...... 53

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11 4 2 Alkenyl bromides with different run length s used in precision research so far. ... 53 4 3 Synthetic attempt for the preparation of alkenyl bromide with 19 methylene run length. ................................ ................................ ................................ .......... 54 4 4 Synthetic attempt for the preparation of butyl branched monomer 4 19 ............ 55 4 5 Successful synthesis of alkenyl bromide 20 bromo eicos 1 ene, 4 23 .............. 56 4 6 Synthesis of 21 alkylhentetraconta 1,40 dienes ( 4 27 a m ). .............................. 57 4 7 Synthesis of precision polymers possessing a branch on every 39th carbon. .... 59 4 8 1 H 500 MHz NMR spectra of monomer ( 4 27h ), unsaturated ( 4 28h ) and saturated ( 4 29h ) polymers ................................ ................................ ................. 60 4 9 13 C 126 MHz NMR spectra of monomer ( 4 27h ), unsaturated ( 4 28h ) and saturated ( 4 29h ) polymers. ................................ ................................ ................ 61 4 10 Infrared spectra for the precisely branched polymers ................................ ......... 62 4 11 C omparison of 13 C NMR spectra for precision polymers. ................................ ... 64 4 12 Commonly accepted nomenclature used to identify the positions of different carbons. ................................ ................................ ................................ .............. 65 4 13 Comparison of 13 C NMR spectra for precision polymers ................................ .... 66 4 14 Comparison of 13 C NMR spectra for precision polymers. ................................ ... 67 5 1 Differential scanning calorimetry thermograms for precision polymers ............... 92 5 2 Differential scanning calorimetry thermograms for precision polymers ............... 93 5 3 Dependence of branch identity on melting point and heat of fusion. .................. 94 5 4 Comparison of the thermal behavior of the precision polymer s .......................... 95 5 5 The CH 2 rocking and scissors band regions for the precisely branched polymers ................................ ................................ ................................ ............. 97 5 6 CP/MAS spectra of precision polymers ................................ .............................. 99 5 7 Wide angle X ray diffraction patterns for precision polymers ............................ 102 5 8 Wide angle X ray diffraction patterns for precision polymers ............................ 103 5 9 Scattering angles of two strong reflections for alkyl branched precision polymers. ................................ ................................ ................................ .......... 104

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12 5 10 Wide angle X ray diffraction pat terns for precision polymers ............................ 105 5 11 Wide angle X ray diffraction patterns for precision polymers ............................ 106 5 12 WAXD pattern s of pre cision polymers ................................ .............................. 107 5 13 Temperature dependent Wide angle X ray diffraction patterns for polymers .... 108 5 14 Temperature dependent Wide angle X ray diffraction patterns for precision polymers ................................ ................................ ................................ ........... 109 5 15 TEM images of precision polymers ................................ ................................ ... 111 5 16 Selected area s ingle crystal electron diffraction patterns of ADMET PE and polymer 4 29a (methyl) ................................ ................................ ................... 112 5 17 Structural model for precision polymer 4 29a (methyl) ................................ ..... 113 6 1 Synthetic strategy to generate alkylating agent with 36 methylene run length. 116 6 2 Synthetic strategy to generate alkylating agent with 29 methylene run length. 117 6 3 Synthetic strategy to generate monomer 6 17 with 29 methylene run length. .. 119 6 4 Synthesis of alkenyl bromide 6 22 with 36 methylene run length. .................... 120 6 5 Synthesis of symmetrical diene monomer with a butyl branch on every 39 th carbon. ................................ ................................ ................................ ....... 121 6 6 Sy nthesis of precision polymers possessing a branch on every 39th carbon. .. 122 6 7 1 H NMR spectra of monomer ( 6 26 ), unsaturated ( 6 27 ) and saturated ( 6 28 ) polymers. ................................ ................................ ................................ .......... 123 6 8 DSC exotherms (down) and endotherms (up) for unsaturated ( 6 27 ) and saturated ( 6 28 ) polymers. ................................ ................................ ............... 124 6 9 Plot of melting temperature vs butyl branch f requency in precision polyethylenes. ................................ ................................ ................................ ... 126 6 10 WAXD diffractograms of precision polymer 6 28 ................................ .............. 127

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13 LIST OF ABBREVIATION S ADMET Acyclic diene metathesis CCD Charg ed Coupled Device DSC Differential scanning calorimetry DART Direct Analysis in Real Time GIF Gatan Imaging Filter GPC Gel permeation chromatography HDPE High density polyethylene HRMS High Resolution Mass Spectrometry NMR Nuclear magnetic resonance IR Inf rared spectroscopy LCB Long chain branching LDPE Low density polyethylene LLDPE Linear low density polyethylene RID Refractive Index Detector SCB Short chain branching TEM Transmission electron microscopy TREF Temperature rising elution fractionation UHMWP E Ultra high molecular weight polyethylene VLDPE Very low density polyethylene WAXD Wide angle X ray diffraction

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14 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirem ents for the Degree of Doctor of Philosophy DECREASING THE ALKYL BRANCH FREQUENCY IN PRECISION POLYETHYLENE By Bora Inci December 2011 Chair: Kenneth B. Wagener Major: Chemistry Metathesis polycondensation chemistry has been employed to control the cr ystalline morphology of Linear Low Density Polyethylene (LLDPE) by precisely introducing the alkyl branches along the polymer backbone. These polymers, while structurally akin to copolymers made via chain copolymerization of ethylene and vinyl comonomers, have unique properties, because use of symmetrical monomers ensures precise spacing of the chain branches An important limitation in this work was the synthesis of the symmetrical diene monomers required in this chemistry. Spacing in the symmet rical monomer directly determines the precision r un lengths in the polymer: P rior monomer synthetic schemes have limited the maximum run lengths between branch points along the polymer to 20 methylene carbons (ie, a branch placed on each and every 21 st car bon). The present work describes the systematic increase of precision run lengths to 38 and 74 methylene carbons. Successful preparation of symmetrical dienes for both run lengths is presented. For the case of 38 run lengths, the synthesis and characterization of precisely sequenced polyethylenes containing thirteen different branches allowed systematic examination of the e ffect of branching on polyet hylene

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15 properties. A clear change in morphology is observed for these polymers from a situation where the methyl branches of greater mass are excluded from the unit cell. T he precision LLDPE model polymers were characterized with Differential Scanning Calorimetry (DSC), Infrared Spectroscopy, Solid State Nuclear Magnetic Resonance Spectroscopy, Wide Angle X ray Scattering (WAXS) and Transmission Electron Microscopy (TEM). Precision polymer with but yl branches on every 75 th carbon was successfully prepared and X ray investigation of this polymer displayed an orthorhombic unit cell structure with the absence of metastable phase formation. Increasing the distance between the two consecutive branche s f rom 38 carbons (5.26 mole% branch concentratio n) to 74 carbons (2.70 mole% branch concentration) fully expels the butyl branches from the crystal lattice to the amorphous phase. This precision polymer with butyl branches on every 75 th carbon represents the first realistic model of commercial LLDPE reported so far in precision polyolefin research.

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16 CHAPTER 1 INTRODUCTION Since it was first produced in large scale in 1936, industrial polyethylene has been the most manufactured polymer worldwide. Depending on the synthetic methodology and polymer processing, polyethylene can be classified as various types, such as high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra high molecular polyethylene (UHMPE ), etc. Each type exhibits distinct macroscopic properties, and consequently has found various broad applications based on performance. To understand the structure property performance relationships of these materials, precision polyolefins are used as mod el structures for commercial polyethylenes. In precision polyethylene, the branch identity and branch frequency can be precisely controlled, while in commercial polyethy lene there are many variables, including the branch size, branch spacer, and branch di stribution. By limiting the freedom of the system, a better understanding of branching in PE can be achieved. An important limitation in this research relates to the concentration of incorporated branches in the final material. So far, the developed monom er synthetic schemes provide the maximum run lengths between branch points along the polymer to 20 methylene carbons, which corresponds to 10 mole% of comonomer incorporation. This document describes the systematic decrease of the comonomer incorporation b elow 10 mole%. This dissert ation is organized as follows: I n Chapter 2, polyethylene and crystallization phenomena are briefly reviewed. The h istoric al significance of polyethylene and different polye thylene structures are discussed Chain folding as well as commonly observed unit cell structures are also discussed.

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17 Chapter 3 describes different branch structures in chain polymerized polyethylene and introduces the precision polyethylene structures Limitations in monomer synthesis are discussed. In Chapt er 4, increasing the branch run length in monomer synthesis is described. Suc cessful preparation of precise polyethylen es possessing alkyl branches on every 39 th carbon is presented. Various alkyl branches ranging from methyl to pentadecyl are incorporated in the polymer backbone. Primary structure delineation of these polymers is discussed. In Chapter 5, morphological characterization of precise polymers is presented. Differential scanning calorimetry (DSC), wide angle X ray scattering (WAXS), transmission electron microscopy (TEM) and solid state nuclear magnetic resonance spectroscopy (ssNMR) investigation results are presented. In Chapter 6, systematic increase of alkyl branch run length in precision polyethylene to yield precision polym er possessing bu tyl branches at every 75 th carbon is presented. Primary structure characterization and morphological examination of this polymer is also described. Chapter 7 presents a summary of the dissertation and suggestions for future work

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18 CHAPTER 2 POLYETHYLENE A ND CRYSTALLIZATION P HENOMENA 2.1 Historic Importance of Polyethylene The first mentioned during the Chemical Society meeting on April 27, 1863 by M. P. E. Berthelot 1 Incidental synthesis of polyethylene from decomposition of diazomethane was reported by von Pechman 2 in 1898 and shortly thereafter by Bamberger and Tschirner 3 white flocculant material and were disappointed about this product because it was not what they had expected to find in their experiments. In a 1930 paper 4 Friedrich and Marvel reported formation of the reaction between alkali metal alkyls and quaternary arsonium compounds. The rapid polymerization reaction was attributed to the presence of alkyl lithium species in the reaction flask and the significance of was not realized. In the early 1930s, W. H. Carothers from Du Pont De Nemours Chemical Company was interested in the by employing the Wurtz reaction with alkyl dibromides 5 He was able to isolate various long hydrocarbons such as n eicosane, n triacontane, n tetracontane, n pentacontane, n he xacontane and n heptacontane by fractional distillation and crystallization. Imperial Chemical Industries in the early 1930s initiated a research program to investigate the high pressure reactivity of selected organic compounds. T he existence of polyethy lene was recognized for the first time i n 1933 by R. Gibbon and E. Fawcett They correctly identified the recovered white waxy solid from the reaction of ethylene and benzaldehyde but the reaction was not reproducible. In December 1935, M. Perrin optimize d the polymerization conditions to consistently produce polyethylene and this

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19 procedure was patented in 1936 6 The success in reproducible polymer synthesis came from the trace amount of oxygen contamination that leads to the formation of free radicals to initiate the polymerization. The first set of experimental conditions gave highly ductile material having a melting point of about 110 o C in a gram scale. This material is now known as low density polyethylene and was utilized in insulatio n applications for submarine communication cables and telecommunication cab les linking France and England during World War II. The superior advantages of polyethylene over the conventional insulators were recognized by Union Carbide and du Pont and both c ompanies obtained licenses from Imperial Chemical Industries to produce polyethylene in the United States. The war related demand for polyethylene diminished in the years following W orld W ar II and companies in the United States and Britain shifted their focus to consumer development. In the United States, the use of polyethylene was expanded into the packaging industry, while in Britain applications for molded items attracted more interest. Despite the desirable properties and various applications of pol yethylene available after World War II a number of cha racteristics limited its general usage such as its low tensile strength, flexibility and its low softening temperature. In addition to its material properties, the extremely h arsh polymerization condi tions (1000 to 2000 atm, 200 o C) required for its the commercial production also hindered the further exploitation of polyethylene. 2.2 Discovery of High Density Polyethylene Investigation of new catalyst systems to polymerize ethylene under milder tempera ture and pressure conditions was an emerging field after the World War II. The most noticeable achievement in catalyst research was made by the German chemi st

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20 Karl Ziegler, who was heading a research group at the Max Planck Institute for Coal Research at M ulheim/Ruhr. As a pure synthetic chemist, Ziegler was interested in preparation and reactivity of metal alkyl compounds in his early career at the University of Heidelberg 7 There, h e observed the addition of butadiene and styrene to the alkali alkyls at room temperature 8 10 In 1943, Ziegler mov ed to the Max Planck Institute for Coal R esearch at Mulheim/Ruhr. H e attempted to transfer because of the availability of ethylene in the Mulheim /Ruhr area from coke manufacture. However, unlike butadiene, the addition product of ethylene and Li alkyls readily decomposed to give lith ium hydride and olefin without any molecular weight increase. After a couple of years of preliminary research, t he di merized product (1 butene) was detected when ethylene addition to the recently discovered lithium aluminum hydride was examined 11 13 Triethyl aluminum was identified as an intermediate for the ethylene addition and E. Holzkamp, a graduate student in the Ziegler group, focused on the pos sible mechanisms of 1 butene formation 14 The t race amount of nickel from the stainless steel reaction vessel was identified to be the reason for the observed chain termination giving 1 butene. The potential for ethylene polymerization was then realized and different transition metals were investigated to control the chain termination Chromium complexes w ere found to catalyze et hylene polymerization to yield a mixture of oligomers and high polymer. In 1953 H. Breil, another graduate student in the Ziegler group, employed a zirconium complex catalyst to form mainly high molecular weight polyethylene 15 H. Martin, a senior staff member in the group, success fully polymerize d

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21 ethylene w it h a titanium complex at low pressure This imp rovement made it possible to conduct the ethylene polymerization in a glass vessel 16 Figure 2 1. Timeline and the significant steps for the development of the catalyst Reproduced from Karl Ziegler Nob el Lecture, 1963. The Nobel Foundation. The d evelopment of the Mulheim catalyst, as Karl Ziegler describes, is illustrated in Figure 2 1. The new form of polyethylene made with this catalyst displayed superi or properties including higher melting point, better mechanical response and eas i er producibility at lower pressures. A v ariety of structures 17 25 have been proposed for the

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22 active species of the Mulheim catalyst. The generally accepted mechanism for ethylene polymerization is depicted in Figure 2 2. Figure 2 2. Mechanism for the Mulheim catalyst used in ethylene polymerization Adapted from Arlman, E. J. et. al 18 As shown in Figure 2 2, TiCl 3 is activated with alkyl alumin um to form c omplex 3 The a ctivated octahedral titanium complex on the surface of a TiCl 3 crystal has an unoccupied site where the ethylene insertion takes place. After the insertion, a new chemical bond forms between the inserted ethylene and the titanium coordinated alkyl. Reorganization of complex 5 generates the active species for the next ethylene insertion to yield linear polyethylene In 1953, K. Ziegler and coworkers began filing patents around the world including in Germany 26 and the US 27 The i mproved prop erties and low production costs of this new polymer attracted considerable attention from several chemical companies around the world. In less than 10 years of its discovery, Mulheim catalyst was utilized in commercial production of high density polyethylene in Europe, the US, Russia and Japan as shown in Figure 2 3

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23 Figur e 2 3 Location of industrial appli cations of the Mulheim process in the world (as of 1963). Numbers indicate the number of chemical plants. Reproduced from Karl Ziegler Nobel Lecture, 1963. The Nobel Foundation. The significance of this discovery was recognized by the Nobel Prize Committee in 1963 when it awarded the Nobel Prize to Karl Ziegle r for his work in the field of ethylene polymerization. 2.3 Towards More Specialized Polyethylene The development of the Mulheim catalyst expanded the range of material properties of polyethylene, and it became However, o ne of the shortcomings of this highly crystalline polymer was related to processing methodologies. High density polyethylene tends to shrink upon cooling and uneven cooling conditions yield warped molded items. R esearch had been directed toward the suppression of crystallization by incorporating pendent side chain s in to the polymer backbone Copolymerization of ethylene with various olefins was the prevailing methodology to modify polymer properties. This new class of polymers is now known as linear low density polyethylene (LLDPE) and was first commercialized in 1960 by D u Pont. The typical comonomers used for copolymerization are 1 butene, 1 hexene

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24 and 1 octene to introduce ethyl, butyl and hexyl branches respectively. The h eterogeneous natu re of the Mulheim catalyst generates nonuniform distribution of branches in linear low density polyethylenes. In addition to a broad composition distribution, molecular the weight distribution is also generally broad ( ) A breakt hrough observation by Kaminsky and Sinn had an enormous impact on the development of new polymerization catalysts and reactions 28,29 They combined titanium and zirconium metallocenes with a hydrated form of trimeth yl aluminum, methylaluminoxane (MAO), to afford an extrem ely active metallocene catalyst The idea of converting cheap starting ma terials to specialized polymers led to an e xplosion of research into the development of metallocene catalysts involving numero us metal s and ligand s 30 33 The h omogeneous nature of these catalysts provides active polymerization sites for every molecule in solution and demonstrates very high activity I n some cases 34 there is a 100 fold activity enhancement compared to the heterogeneous Mulheim catalyst resulting in the production of 300 metric tons of polyethylene per gram quantity of catalyst in one hour. In addition to high activity, metallocene catalysts can produce polyolefins with narrow molecular weight distributions ( ). For the case of LL D PEs, incorporati on of olefins can be controlled to yield homogeneous distributions of pendent branches in the polyethylene backbone Homo and copolymerization of e thylene with late transition metals became an active field of research in the mid 1990s with a family of new cat ionic Pd(II) and Ni(II) diimine catalysts introduced by Maurice Brookhart and his coworkers at DuPont 35 45 Late transition metal complexes are known to have lower olefin insertion rates

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25 compared to early transiti on metal catalysts and hydride elimination typically competes with chain growth yielding dimers and oligomers. Brookhart`s catalysts were designed to have highly electrophilic cationic metal centers resulting in rapid rates of olefin insertion. Moreover sterically bulky diimine ligands favor insertion over chain transfer. Alteration s of the ligand structure result ed in control of branching to obtain a variety of materials ranging from highly crystalline HDPE to hyperbranched oils from the sam e feedsto ck. Functional group tolerance is a nother important feature of these type s of catalysts where some of the late transition metals, especially cationic palladium diimine complexes polymerize ethylene in the presence of ethers, organic esters and acids 46 Brookhart and others employed t his catalyst system f or the copolymerization of ethylene and/or olefins with commercially important a crylates 37,40,47,48 and carboxylates 37,49 to yield high molecular weight and random copolyme rs Aqueous emulsion and suspension polymerizations have also been developed 50 52 as a route to microspheres of polymer for adhesives proving the possibility of insertion into the catalyst and chain growth in the presence of water. 2.4 Polyethylene Classifications As mentioned above, many types of polyethylene exist. The versatility of p olyethylene based materials arises mainly from branching, which can be directly in the polymer limit the packing ability of chains and polyethylene samples that have few branches exhibi t a higher degree of crystallinity than those that have many. Since the packing of crystalline regions is better than that of noncrystalline regions, the overall density of polyethylene will increase as the degree of crystallinity increases. The degree of branching varies the density and morphology of polyethylene from purely crystalline (1.00 g/cm 3 ) to totally

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26 amorphous (0.850 g/cm 3 ) Based on its density and branching, polyethylene is traditionally classified into three categories : l ow density polyethylen e (LDPE), high density polyethylene (HDPE), and linear low density polyethylene (LLDPE) Recent advances in the area of metallocene catalysts have expanded the nomenclature to include ultra high molecular weight polyethylene (UHMWPE) and very low density p olyethylene (VLDPE). Figure 2 4. Types of polyethylenes: A ) high density polyethylene, B ) low density polyethylene, C ) linear low density polyethylene, D ) very low density polyethylene. High density polyethylene (HDPE), as de picted in of Figure2 4A has a typical density range of 0.94 0.97 g/cm 3 It exhibits an extremely low level of branches and high degree of crystallinity. Since HDPE has negligible branching in its backbone, the chemical structure of this polymer is the clo sest to pure polyethylene and is often a) b) c) d)

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27 referred to as linear polyethylene. In most cases, HDPE shows 60 80% crystallinity an d good mechanical strength ( Table 2 1 ) HDPE is a stiff and opaque material and is used widely in grocery bags, pipes, bottles and t oys, etc. Global HDPE demand was estimated at 32 million tons in 2009 and corresponds to 45 % of total polyethylene production 53 Low density polyethylene (LDPE), or hig h pressure polyethylene, is named due to its relatively low density caused by substantial concentrations of branches. Formation of branches decreases the density of polyethylene to the range of 0.90 0.94 g/cm 3 T he most commonly observed branches are ethyl and butyl groups as well as l ong chains. High pressure polymerization conditions and radical chemistry randomly distribute long chain and short chain branches along the backbone. As shown in Figure 2 4B long c hain branches can themselves be branched to give a soft and flexible material. It displays lower melting transition than HPDE and is mostly used in the packaging industry. The number of LDPE production sites decreases annually mainly because of the high p roduction costs. Global LDPE demand was estimated at 18 million tons in 2009 and corresponds to 27 % of total polyethylene production 53 Linear low density polyethylene (LLDPE) is a linear version of polyethylene possessing short alkyl chains at random inte rvals shown in Figure 2 4C This type of polymer is produced by the copolymerization of ethylene and olefins. The most c ommon monomers used for copolymerization are 1 butene, 1 hexene and 1 octene to give ethyl, butyl and hexyl branches, respectively. LLDPE resins may also contain small levels of long chain branches. Metallocene catalysts are most commonly used to produce L LDPE yielding narrower molecular weight distributions compared to HDPE

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28 and LDPE. Linear low density polyethylene is predominantly used in the packaging industry due to its good mechanical properties and relative tran sparency. Global LLDPE demand was esti mated at 19 million tons in 2009 exceeding the us e of LDPE and corresponding to 28% of total polyethylene production 53 Tab le 2 1. General properties for various commercial polyethylenes Data adapted from Handbook of polyethylene: structures, properties and applications 2 Very low density polyethylene (VLDPE) is a specialized form of linear low density polyethylene having a much higher concentration of short chain branches as illustrated in Figure 2 4D This level of branching suppresses crystalline structure to yield materials with very low crystallinity. In some extreme cases, totally amorphous materials can also be obtained (Table 2 1). Similar to linear low density polye thylene, VLDPE is also produced by a metallocene catalyst. Th ese specialty polymers are mainly utilized in tubing food containers and packaging applications. Ultra high molecular weight polyethylene (UHMWPE) is a special type of high density polyethylene with extremely long chains. Typical molecular weights are in the order of millions, usually between 2 and 6 million. UHMWPE fibers, commercialized in the late 1970s by DSM, are widely used in defense application s, ballistic s protection and hip replacement. Property HDPE LDPE LLDPE VLDPE Density (g/cm 3 ) 0.94 0.97 0.91 0.94 0.90 0.94 0.86 0.90 Crystallinity (% from density) 62 82 42 62 34 62 4 34 Crystallinity (% form calorimetry) 55 77 30 54 2 2 55 0 22 Tensile modulus (kpsi) 155 200 25 50 38 130 <38 Tensile strength (kpsi) 3.2 4.5 1.2 4.5 1.9 4.5 2.5 4.5 Melting temperature ( o C) 125 132 98 115 100 125 60 90 Industrial production low pressure Ziegler high pressure radical metallocene Ziegler metallocene Number of branches per 1000 carbons 5 7 20 30 10 25 numerous

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29 2.5 Polyethylene Morphology 2.5.1 Chain Folding and Lamella Formation polymer chains in the solid or molten state. Soli d polyethylene exhibits a three phase morphology as illustrated schematically in Figure 2 5. Figure 2 5. Schematic representation of three phase morphology. In this typical semi crystalline morphological model, ordered polyethylene chains (crystalline phase) are surrounded by a disordered, noncrystalline phase. The boundary betwe en these two phases is composed of a partially ordered interfacial layer. The nature of the crystalline phase was clarified by the discovery of chain folding and lamellae in 1957 independently by Till 54 Fischer 55 and Keller 56,57 Thickness measurements on polymer single crystals grown from dilute solution revealed the existence of chain folding and ruled out the previously accepted 58 60 fringed micelle

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30 model. The typical single crystal thicknesses (10 12 nm) repo rted by Keller and others is much smaller than the length of a polymer chain (100 nm). Figure 2 6. A ) Transmission electron microscopy bright field image of HDPE single cr ystal grown from 0.03 % C 2 Cl 4 solution, B ) S chematic drawing of polyethylene single crystal with regular chain folding 61 The strong evidence for chain folding and lamella formation was the birth of the modern c rystalline polymer morphology. The t ransmission electron microscopy (TEM) image of an HDPE single crystal grown from dilute tetrachloroethylene solution is illus trated in Figure 2 6A The s i ngle crystal observed in this TEM image is schematic ally reproduced in Figure 2 6B to better show the lamella formation and chain folding. Sufficiently long monodisperse n alkanes showing chain folding were independently synthe sized by Whiting 62 and Wegner 63 Long n alkanes ranging from C 102 H 206 to C 390 H 782 were prepared and crystals from both solution and the melt were

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31 systematically analyzed. While n alkane C 102 H 206 could only be obtained in chain extended form, chain folding was found in all n alkanes longer than C 150 H 302 and many or ders of small angle X ray diffractions were observed due to the high regularity of lamella stacking 64 Preparation of sufficiently long n alkanes allowe d the first accurate calculation of lamella spacing. 2.5.2 Unit Cell Structure The c rystal structure of a polymer is built up from many periodic repeating entities c alled unit cells, each having representative information about the structure A specific unit cell can be described by length s (a, b, c) and angle s ( ) parameters as illustrated in Figure 2 7A Figure 2 7. The observed unit cell structures in n alkanes and polyethylene: A ) schematic representation of a typical unit cell, B ) orthorhombic unit cell, C ) monoclinic unit c ell, D ) triclinic unit cell, E ) hexagonal unit cell (Figure adapted from ref. 2) Crystal structure and unit cell analysis of n alkanes and polyethylene started with the d evelopment of X ray crystallography in the early 20 th century T he first crystallogra phic investigation of long hydrocarbons (in this case C 29 H 60 ) was performed by Muller 65 in 1928. Methylene units in C 29 H 60 form a zig zag pattern (all trans configuration) and the C C bond length is found to be 1.52 Crystalline n alkanes have a) b) c) d) e)

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32 been e xamined for decades and their properties were extrapolated to represent the crystalline phase of polyethylene. The c rystal structure 66 68 crystal growth and morphology 69,70 melting temperature 71,72 and chain mobility 73 75 of n alkanes have been evaluated and extensively reviewed 76,77 Figure 2 8 Polyethylene orthorhombic unit cell with Pnam D 2h space group. A) orthogonal view, B ) view along the c axis (Figure adapted from ref. 2). A complete unit cell and space group determination study for the long paraffin C 60 H 122 was first report ed in 1939 by Bunn 78 The orthorhombic unit cell with the space group Pnam D 2h contains 4 CH 2 groups and the all trans chains are parallel as shown in Figure 2 8. The same crystal structure is also observed 79 for HDP E with the unit cell parameters: a=7.4069 b=4.9491 and c=2.5511 giving a crystal density of 0.996 g/cm 3

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33 T he dimensions of the orthorhombic unit cell are not constant. Due to the effect of branching, LDPE and LLDPE exhibit la rger a and b ax is dimensions than HDPE. The i ntroduction of branches in to polyethylene backbone not only affects the unit cell dimensions, but also generates metastable crystal forms. The commonly observed metastable phases are shown in Figure 2 9. According to Seto 81 e t al., t he d imensions of the monoclinic unit cell of linear polyethylene are found to be a=8.09 b=2.53 and c=4.79 giving a crystal density of 0.998 g/cm 3 A m onoclinic crystal form was also observed for ethylene/ olefin copolymers in the absence of mechanical stress 82 Figure 2 9. Metastab le polyethylene unit c ells. A ) M onoclinic unit cell and B ) H exagonal unit cell (Figure adapted from ref. 2). The hexagonal form of poly ethylene, shown in Figure 2 9B is generated under high temperature and pressure conditions and was first observed by Bassett 83 et al. The hexagonal phase has very special translational chain mobility characteristics which allow polyethylene to be easily processed under these conditions. Ethylene/1 propene copolymers having propylene content higher than 20 mol % exhibit a hex agonal crystal structure at room temperature and under normal pressure conditions 84 It is important to note that the m etastable unit cel ls shown in Figure 2 9 both feature a higher distance between neighboring chains (extended a axis) compared to a n orthorhombic unit cell.

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34 CHAPTER 3 ALKYL BRANCHED PRECI SION POLYETYLENE 1 3.1 Branching in Polyethylenes The presence of bran ching in polyethylene has significant effects on material properties such as density, degree of crystallinity, mechanical strength and processability 2 Predictable alterations on the performance of polyethylene can be achieved by controlling the amount and the distribution of branching on the polyethylene backbone. Depending on the mode of polymerization, catalyst type, pressure and temperature the nature of the branch varies and is classified as s h ort chain branching (SCB) or long chain branching (LCB) 3.1.1 Short Chain Branching Regar dless of the conditions sh ort chain branching (SCB) inevitably forms during the chain growth polymerization of polyethylene. In tramolecular chain transfer of the reactive center results in SCB for radical and metal mediated polymerizations 85 The generally accepted mechanism for the formation of various SCB s in LDPE is illustrated in Figure 3 1. Propagating radical species 3 1 abstracts hydrogens from the fifth, sixth and seventh methylene groups to yield n butyl, n pentyl and n hexyl branches, respectively. n B utyl branches are more abundant than others due to th e formation of a six m embered transition state (five carbons and the hydrogen being ab stracted) during the hydrogen abstraction 86 Reactive radical species 3 2 can take up another available ethylene monomer to give species 3 5 which can either propagate linearly to form an n b utyl branch or abstract another intramolecular hyd rogen through different pathways to 1 Part of this chapter is adapted with permission from (Rojas, G.; Inci, B.; Wei, Y.; Wagener, K. B. Journal of American Chemical Society 2009 131, 17376). Copyright (2009) American Chemical Society.

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35 yield 2 ethyl hexyl and 1,3 diethyl branches. Short chain branches in LDPE have significant effects on chain packing where the maximum crystallinity of 60 70% can be achieved by free radical polymerization of ethylene. Figure 3 1. Generally ac cepted mechanism for the formation of n butyl, n pentyl, n hexyl, 1,3 diethyl and 2 ethylhexyl branches in LDPE (Figure adapted from ref. 86 )

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36 Small concentrations of the u ndesired SCB can also be observed in HDPE prepared by Ziegler and metallocene chemis try. For example, ethyl branches up to 2 mol% are reported in the polymerization of ethylene by metallocene catalyst s 87 The situation is somewhat different for late transition metal mediated ethylene polymerization. Compared to early transition metal based catalyst (e.g. Ziegler and metallocene), late transition metal catalysis exhibit reduced activities for olefin insertion and hydride elimination which typically compete with chain growth 44 Figure 3 2. Suggested mechanism for sec butyl branch format ion 44 For example, e lucidation of highly branched nickel catalyzed polyethylene with 13 C NMR techniques revealed the formation of methyl, ethyl, n butyl, n pentyl, n hexyl and sec butyl branches in the polymer backbone 88

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37 The exist ence of s hort chain branching is not always an undesired phenomenon. For the case of linear low density polyethylene, SCBs are intentionally incorporated along the polyethylene chain to tune the properties LLDPE resins exhibit high film tear strength rel ative ly high clarity and ease of processability. Because of these attractive properties, LLDPE films are extensively used in the packaging industry. Commercial LLDPE is prepared by chain growth polymerization using Mulheim or metallocene chemistry 2 although r ecently late transition metal mediated copolymerization is also becoming more popular 35,36 The absence of multisite initiation in single site metallocene and late transition metal systems results in the synthesis of copolymers possessing narrower molecular weight dist ribut ions and higher levels of olefin comonomer incorporation 33,34,44 3.1.2 Long Chain Branching The presence of long chain branching (LCB) in LDPE has been known for decades 89 92 Intermolecular chain transfer of a radical propagating center results in fo rmation of LCBs which significantly affect the rheological behavior of LDPE and improve its processability 93 95 Even though most of the properties of LDPE are generally inferior to those of LLDPE, the former still has a large market share due to its greater processability. than ~70 methylene units, correspond ing to the critical entanglement mol ecular weight of polyethylene (i.e ~1000 g/mol) 96 The co ncept of long chain branching was revisited in the 1990s for its possible application in the field of metallocene polyethylene. Metallocene catalysts generate polymers of narrow molecular weight distribution with superior thermal and mechanical properties 31 However, t hese polymers suffer from poor processability (e.g., high

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38 susceptibility to melt fracture) mostly due to the narrow molecular weight distribution. Recent advances in catalyst technology have resulted in metallocene polymers containing small amounts of LCB to ease the processability while still maintaining superior properties 97,98 The constrained geometry cata lyst developed at Dow Chemical was the first single site catalyst discovered to generate long chain branched polyethylene 99,100 The LCB is believed to be incorporated in to the polymer backbone via the insertion of vinyl terminated macromon omers in to the catalyst 31 3.1.3 Quantification of Branching in Polyethylene By their nature, b oth radical and metal mediated chain propagation chemistr ies generate branches t hrough uncontrolled intramolecular and intermolecular chain transfer Inevitable chain transfer an d chain walking processes produce alkyl branches of varying lengths randomly spaced along the polyethylene backbone 101 Several methods have been developed to identify the branches and quantify their distribution in the main chain 102 106 Gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), light scatt ering and rheological measurements are frequent ly used to elucidate branching. GPC is ineffective in measuring low levels of branching and rheological examination only provides indirect evid ence for branching. NMR can quantify only linear branches from me thyl to pentyl as it cannot effectively distinguish short chain and long chain branches once the branch length exceeds six carbon atoms in length 107 For the case of LLDPE, quantification of branches becomes even more challenging. In addition to intentionally incorporated branches from copolymerization with olefins undesired branching also occurs, resulting in more complex system s Analytical and preparative scale Temperature Rising Elution F ractionation (TREF) was

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39 developed to prepare components with narrower distributions of molecular weight and branchin g 108 110 TREF is a technique that fractionates polymer chains based on their individual crystallinity. Since branching directly affects the crystallinity of polyethylene, TREF can fractionate LLDPE chains based on branch concentration 111 3.2 Structure of Precision Branched Polyethylene As described in the previous section, conventional ethylene polymerization methodologies generate branches of varying lengths randomly spaced along the polyethylene backbone. The uncontrolled nature of branc hing in these polymer systems preven ts the comprehensive primary structure delineation and possible tertiary structure correlations. Recently, pre cise polyethylene structures were introduced to better understand the influence of branching on macroscopic properties 112 120 A representative structure of these polyme rs is illustrated in Figure 3 3 where the identity of the branch and its position along the polyethylene chain is known without eq uivocation. Figure 3 3 General chemical structure of pre cision polyethylene. Branches with known identity are incorporated regularly (in this case 20 methylene units between branches) along the polyethylene backbone. Acyclic Diene Metathesis (ADMET) Polymerization is emp loyed to generate these precisely branche d polyethylene s 121,122 A wide variety of branches such as, alkyl 112 114,116 120 halide 123 128 acid 129 133 siloxane 134 137 and biologically active 138 144 groups can

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40 be precisely incorporated in to the polyethylene backbone with this mild polymerization chemistry. 3.3 Synthesis and Properties of Precision Branched Polyethylene s The historic background and utility of ADMET has recently been reviewed in detail 145 147 Thus, only its application in the field of precision alkyl b ranched polyethylene will be discussed herein. The g eneral synthetic scheme for this chemistry is illustrated in Figure 3 4 Symmetrical diene monomers are cond ensed into unsaturated polymers br Figure 3 4. General two step synthetic scheme for the preparation of precision branched polyethylene. Typical polymerizations are performed in bulk and ethylene is removed under vacuum to yield hi gh conversion, which is necessary for any ste p growth polymerization. Monomers are required to be highly pure (>99%) and only one mechanism (metathesis) should be opera ting during the polymerization to ensure the precise placement of branches Well defined metathesis catalysts are utilized to fulfill these requirements. As shown in Figure 3 4, monomer synthesis is the key in this research because the b ranch identity and the distance between the branches are set in this step. Several synthetic

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41 routes have b een developed to incorporate alkyl branches with various lengths along the precision branched polyethylene. 3.3.1 Methyl Branch Symmetrical diene monomers possessing methyl branches were first prepared by alkylating ethyl acetoacetate 112 114 with alkenyl bromide to give compound 3 18 As illustrated in Figure 3 5, retro Claisen condensation yields d eacylated product, compound 3 19 which is subsequently reduced to a primary alcohol. Compound 3 20 is tosylated and su bsequent hydride displacement generate s monomer 3 22 Depending on the run length the overall yield varies in the range of 25 30%. Figure 3 5. Synthesis of methyl branched monomers 112 114 Alkenyl bromides of different sizes are utilized in the alkylation step to give methyl branches on every 9 th 11 th 15 th 19 t h and 21 st carbons in the polyethylene backbone. Synthesis of the m ore frequent methyl branch placement in the polymer chain was also attempted with shorter alkenyl bromide run lengths. Although the monomers were successfully prepared, high molecular weigh t polymers could not be isolated due to cyclization. An alternative synthetic route was utilized to generate polymers with methyl

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42 branches on every 5 th and 7 th carbons 117 This synthetic approach is depicted in Figure 3 6 where diethyl malonate chemistry is applied for the preparation of both monomers 3 30 and 3 33 Figure 3 6. Synthesis of methyl branched monomers with short ethylene run leng th 117 In this scheme, d ialkylation of either 1,6 dibromohexane or 1,4 dibromobutane with diethyl alkenyl malonate generates a tetraester diene, which is then converted to the tetraacid diene after saponification and decarboxylation. Reduction to a diol and subsequent mesylation and reductive cleavage with hydride gives the desired

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43 monomers 3 30 and 3 33 Polymerization and hydrogenation of these monomers yield polyethylenes possessing a methyl branch on every 7 th and 5 th carbons. Thermal and molecular weight data for the series of polyethylenes having methyl branches with various run lengths are presented in Table 3 1. In contrast to chain polymerized ethylene/propylene copolymers 108 precise polymers exhibit sharp and well defined ther mal transitions as a result of control of branch identity and placement. Table 3 1. Effect of precise methyl branch placement on thermal properties Methyl branch on every n th carbon 1 propene c omonomer content (mole%) T m ( o C) (peak) H m (J /g) ( k g/mol) no branch 0 134 204 25 8 21 10.0 62 103 20.2 19 11.1 57 96 72.0 15 14.3 39 82 17.1 11 20.0 11 66 8.50 9 25.0 14 28 17.5 7 33.3 60 19 12.9 5 50.0 amorphous -28.4 It is also interesting to compare the thermal behavior of these precise polymers with unbranched polyeth ylene prepared with ADMET polymerization of 1,9 decadiene. ADMET polyethylene compares well with chain polymerized commercial polyethylene. (Both preparations melt at 134 o C and form orthorhombic unit cells.) Introduction of methyl groups onto the polyethylene backbone disrupts the crystallinity As the concentration of methyl branches increases both the melting point and heat of fusion gradually decrease and a morphous polymer forms when the met hyl branches are placed six carbons apart in the polymer backbone. As shown in Table 3 1, preparation of model polymers with this precision approach gives the opportunity to tune the melting point of polyethylene over a range of 200 o C.

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44 Symmetrical diene monomers are also copolymerized with 1,9 decadiene to produce a series of polymers whose thermal behavior and spectroscopic features begin to mirror those of commercial linear low density polyethylene (LLDPE). In addition to intentionally introdu ced SCBs with ethylene copolymerization of olefins, commercial LLDPEs possess undesired branches which prevent the primary structure elucidation. The situation is quite different in irregularly spaced methyl branched ADMET polymers. Copolymerization of diene monomers with 1,9 decadiene yields polymers having only methyl branches and their concentration can be systematically be varied by the changing feed ratio of the monomers. Figure 3 7. Thermal behavior of polyethylene having A ) precisely spaced m ethyl branches and B ) randomly spaced methyl branches. The DSC thermogram of irregularly spaced methyl branched polyethylene (Figure 3 7) exhibits a broad melting transition consistent with its commercial analogues In contrast, p recise placement of methyl branches on every 21 st carbon results in a w ell defined thermal transition. The effect of methyl branch inclusion into the polyethylene

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45 backbone on the crystal structure was also investigated 115 For example, introducing methyl branches on every 21 st carbon shifts the unit cell from orthorhombic to triclinic. 3.3.2 Ethyl and Hexyl Branches Successful preparation of precisely plac ed methyl branches in polyethylene with ADMET stimulated efforts to model mainstream LLDPEs such as ethylene/1 butene and ethylene/1 octene The s ynthetic scheme for the preparation of ethyl and hexyl branched monomers is illustrated in Figure 3 8 Figure 3 8. Synthesis of ethyl 116 a nd hexyl 118 branched monomers. As shown in Figure 3 8, t he key alcohol i ntermediate (compound 3 37 ) for the synthesis of both monomers is generated through dialkylation of diethyl malonate ( 3 23 ), saponification, decarboxylation and reduction steps. Bromination of the primary alcohol and subsequent addition of solid CO 2 to the Grignard intermediate gives an acid

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46 diene ( 3 39 ). After reduction of the acid and bromination steps, another Grignard reagent forms and is quenched with H 2 O to yield the ethyl branched symmetrical monomer ( 3 41 ). The overall yield s for this multistep synt hetic route are in the range of 20 25 %. For the synthesis of hexyl branched monomer, primary alcohol ( 3 37 ) is first converted to the sulfonic acid ester (compound 3 42 ) intermediate using mesyl chloride. A modi fied Grignard/Gilman reaction was developed to install hexyl branches in the presence of 1 bromopentane. Hexyl branched monomer 3 43 is recovered with overall yield s within the range of 15 20 %. Mon omers were polymerized and hydrogenated to yield precision branch ed polymers. The thermal data for ethy l branched polymers presented in Table 3 2. Similar to the methyl branched polymers, introduction of branch defects in to the polymer backbone decreases both the melting point and the heat of fusion. Incorporation of an ethyl branch on every 21 st carbon dis rupts the crystallinity of linear ADMET polyethylene as indicated by the decrease in T m and H m from 134 o C to 35 o C and 204 J/g to 57 J/g, respectively. Table 3 2. Effect of precise ethyl branch placement on thermal properties Ethyl branch on every n th carbon 1 butene comonomer content (mole%) T m ( o C) (peak) H m (J /g) ( k g/mol) no branch 0 134 204 25 8 21 10.0 35 57 28.0 15 14.3 33 & 6 NA 27.9 9 25.0 amorphous -31.4 M odel ethylene/ 1 butene copolymers synthesized using e ither metallocene 148,149 or hydrogenated butadienes 150,151 with similar net concentration s of ethyl branches

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47 display very ill defined melting endotherms. The reduction of met hylene sequence length to 15 causes the melting point to drop well below room temperature and t he melting endotherm becomes less defined as shown by the bimodal transition Table 3 3 Effect of precise hexyl branch placement on thermal properties Hex yl branch on every n th carbon 1 octene comonomer content (mole%) T m ( o C) (peak) H m (J /g) ( k g/mol) no branch 0 134 204 25 8 21 10.0 16 53 28.0 15 14.3 48 19 24.7 9 25.0 amorphous -24.8 E thylene/1 octene copolymers const itute approximately 25% of the LLDPE market and their thermal and material behavior has been well studied 152 155 As shown in Table 3 3, incorporation of larger hexyl branches at precisely spaced run lengths disrupt s the crystallinity of linear ADMET polyethylene to a higher degre e than methyl and ethyl branches in precision polymers. 3.3.3 Universal Synthesis Route to Symmetrical diene Monomers As mentioned in previous sections and illustrated in Figure 3 4, preparation of symmetrical diene monomers is the key in this research. So far, a lkylation of malonate derivatives has been successfully employed to yield pure diene mon omers 114,116 118 One of the limitations in this chemistry relates to the required multistep transformations specific to each monomer The relatively low ( 15 30% ) overall yield s of malonate route changed the directi on of precision rese arch towards the nitrile chemistry. This new approach is based on the double alkenylation of the primary nitrile 156 followed by the reductive elimination of the nitrile moiety 157 Figure 3 9 shows the

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48 synthetic scheme for the preparation of diene monomer (compound 3 46 ) in two steps with reasonably high (>80%) overall yield. Figure 3 dien e monomer synthesis 156,157 Alkenylation of primary nitrile 3 44 in the presence of lithium diisopropyl amide (LDA) and alkenyl bromide produces the alkylcyano diene 3 45 in high yield Decyanation of nitrile 3 45 is achieved with potassiu m metal via radical chemistry. The resulting tertiary radical after decyanation is further quenched by abstraction of hydrogen from t BuOH to give symmetrical diene monomer 3 46 in quantitative yield Figure 3 10. Incorporation of branches from methyl to adamant yl on every 21 st carbon. The ease of monomer synthesis has significantly expanded the scope of precision polyethylene studies For example, a series of branc hes from methyl to adaman tly were incorporated ( Figure 3 10) in the polyethylene chain on every 21 st carbon to examine the effect of branch identity on thermal and morphological behavior 158 Previously discussed methyl and ethyl branche d polymers were regenerated utilizing the

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49 alkylation/decyanation route and essentially the same thermal behavior was observed for both as shown in Table 3 4. Table 3 4 Molecular weights and thermal data for precision polymers M w (kg/mol) (PDI) Branch identity on every 21 st carbon T m ( o C) (peak) H m (J /g) Unsaturated Saturated No branch 134 204 70.2 ( 2.7 ) 70.2 ( 2.7 ) Methyl 63 104 20.2 (1.7 ) 20.2 (1.7 ) Ethyl 35 65 50.2 ( 1.9 ) 50.7 (1.9 ) Propyl 12 60 41.2 (1.7 ) 41.4 (1.7 ) Butyl 12 57 41.5 (1.8 ) 40.3 (1.7 ) Pentyl 14 58 45.1 ( 1.8 ) 45.8 (1.8 ) Hex yl 12 49 44.6 ( 1.8 ) 46.1 (1.7 ) iso propyl 11 37 45.5 ( 1.7 ) 46.0 ( 1.7 ) i so butyl 9 43 43.0 (1.6 ) 42.6 (1.9) tert butyl 13 50 30.6 (1.7 ) 32.1 (1.7 ) Cyclohexyl 9 37 32.5 (1.6 ) 33.6 ( 1.6 ) Adamantyl 8 & 17 2 & 8 64.7 (1.7 ) 70.8 (1.3 ) The data in Table 3 4 show that the incorporation of m ethyl and ethyl branches reduce s the melting point of linear ADMET polyethylene in a progressing manner; on the other hand, all further branches, from propyl to adamantyl produce polymers that have essentially the same me lting point. There is a clear change in the morphology of these polymers from a situation where the branch (methyl or ethyl) is included in the are excluded from the unit cell as evidenced by wide angle X ray diffraction (WAXD) (Figure 3 11) ADMET polyethylene exhibits t he t ypical orthorhombic crystal structure with two characteristic crystalline peaks superimposed with the amorphous halo exactly the same as for high density polyethylene made by c hain propagation chemistry The more intense peak at scattering angle 21.5 o and the less intense one at 24.0 o correspond to reflection planes (110) a nd (200), respectively. Upon introducing precisely placed

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50 branches of known identity the crystal structure loses its symmetry with the unit cell shifting from orthorhombic to triclinic Figure 3 11. Wide angle X ray diffraction patterns for seven precision polymers: ADMET PE at 27 o C (no branch, T m = 134 o C), 3 49a (methyl) at 27 o C (methyl branch, T m = 63 o C), 3 49b (ethyl) at room temperature ( ethyl branch, T m = 35 o C), 3 49c (propyl) at 0 o C (propyl branch, T m = 12 o C), 3 49d (butyl) at 0 o C (butyl branch, T m = 12 o C), 3 49h ( iso butyl) at 0 o C ( iso butyl branch, T m = 9 o C), 3 49e (pentyl) at 0 o C (pentyl branch, T m = 14 o C) Prior to measurements, all samples were heated to above the melting temperature in order to remove thermal history, and then cooled to a specific temperature at a rate of 1 o C /min.

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51 Moreover, in contrast to linear polyethylene, scattering occurs at relativ ely lower scattering angles and with broader reflections being displayed, suggesting the increase of crystal lite size and a decrease of crystallinity. In the case of the methyl branched polymer s 3 49a (methyl) two r eflections representing a triclinic crys tal orientation occur at scattering angle s of 19 .0 o with Miller index (100) and 22 o with Miller index (010). Similar changes in the crystalline unit cell identity were observed in the ethyl branched polymer, 3 49b (ethyl) Two strong reflections shift to l ower scattering angles ( 1 8 .0 o and 21 .0 o ) compared to the methyl branched polymer ( 1 9 .0 o and 22 .0 o ) According to Bragg`s Law, the lower scattering angles correspond to larger d spacings, indicating that the ethyl branch is incorporated in the crystalline region. For the polymers possessing bulkier branches (propyl or larger), the WAXD diffractograms (the top four graphs in Figure 3 11) show nearly identical scattering patterns, indicating the crystal structure is independent on the branch identity. Moreove r, these patterns are obviously different from those of polymers possessing smalle r branches like methyl or ethyl, because they exhibit larger scattering angle s and even broader reflections. 3.4 Dissertation Purpose Alkyl branched precision polymers prepar ed by ADMET are excellent candidates for modeling commercial LLDPEs. This approach generates polymers where both the identity of the branch and its position along the chain are known without ambiguity. However, the monomer synthetic schemes developed so fa r provide maximum run lengths between branch points to 20 met hylene carbons, which corresponds to 10 mole % of comonomer incorporation This is considerably greater than the comonomer

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52 concentrations in commercial LLDPEs (2 5 mole%), which produces m aterials with melting po ints in the range of 100 to 125 o C as shown in Table 2 1. The remaining chapters in this dissertation describe the systematic increase of run lengths between branch points to 39 and 75 carbons This level of advancement in monomer synthesis generates polymers that provide realistic models for commercial LLDPE.

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53 CHAPTER 4 SYNTHESIS OF PRECISI ON POLYETHYLENE WITH BRANCHES ON EVERY 39 TH CARBON 2 4.1 Monomer Synthesis P reparation of a symmetrical diene monomer is vital to success in precisi on polyethylene research because the built in branch run length strictly dictates the spacing between the two consecutive branch points in the final polymer as shown in Figure 4 1). Figure 4 1. General two step synthet ic scheme for the preparation of precision branched polyethylene. Increasing the run length in monomer 4 1 requires reproducible synthesis of the alkylating agent. Both the malonate 114,116,118 and nitrile 119,120,156 synthetic routes reported so far utilize alkenyl bromides with a maximum of 9 methylene run lengths (Figure 4 2) Figure 4 2. Alkenyl bromides with different run lengths used in precision research so far All of the three alkylating agents shown in Figure 4 2 are commercially available and introduction of these alkenyl bromides into the monomers generate s polyethylenes 2 Part of t his chapter is adapted with permission from (Zuluaga, F.; Inci, B.; Nozue, Y.; Hosoda, S.; Wagener, K. B. Macromolecules 2009 42, 4953). Copyright (2009) American Chemical Society.

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54 with a branch on every 9 th 15 th and 21 st carbons in the polym er backbone, respectively. Alkenyl bromides with higher methylene run lengths are not com mercially available and preparation of these compounds is required. Encouraged by the success of the previously reported 156,157 alkylation/decyanation synt hetic route in monomer preparation synthesis of compou n d 4 13 was attempted from commercially available starting material 11 bromo undec 1 ene 4 6 Figure 4 3. Synthetic attempt for the prepa ration of alkenyl bromide with 19 methylene run length. As shown in Figure 4 3, alkenyl bromide 4 6 was converted into alkenyl cyanide which was subsequently alkylated with 1 equivalent of commercially available 1,10 dibromodecane 4 8 In addition to the desired mono alkylated product 4 9 di alkylated compound s 4 10 and 4 11 were recovered in the crude product. Compound 4 9 was purified by column chromatography and recovered in moderate yield (65%). The same d ecyanation conditions developed for the monome r synthesis 157 were applied to compound 4 9 to yield alkylating agent 4 13 with 19 methylene run lengths. Two different products were identified by thin layer chromatography (TLC) analysis and the presence of elimination product 4 12 was confirmed by 1 H nuclear magnetic resonance

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55 (NMR) spectroscopy. Because of the nearly unnoticeable polarity difference between these species, colum n chromatography purification was not performed and the desir ed product 4 13 could not be isolated. The l ow overall yield, the use of highly toxic KCN and the required tedious purification f or the synthesis change d our focus towards a malononitrile route Figure 4 4. Synthetic atte mpt for the preparation of butyl branched monomer 4 19 The s ynthetic scheme shown in Figure 4 4 eliminates preparation of the alkenyl bromide and targets the direct synthesis of monomer 4 19 which will generate a precision polymer with a butyl branch on every 42 nd carbon. In this route, c onsecutive a lkylation of malononitrile 4 14 with commercially available 11 bromo undec 1 ene 4 6 and 1,10 dibromodecane 4 8 gives compound 4 16 in relatively high yield (two steps 78%). Then hexanenitrile 4 17 is alkylate d by 2 equivalents of compound 4 16 in the presence of lithium diisopropyl amide (LDA) using the same alkylation conditions reported before 156 S pots for both di alkylated malononitrile 4 16 and hexanenitrile 4 17 disappe ared on the TLC plate within 2 hours but many other s pots formed. Chan ging the reaction conditions did not decrease the number of spots and the desired product 4

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56 18 could not be isolated. The difficulties in the alkylation step of this synthetic scheme decrease d the motivation to pursue this route further T he successful s ynthesis of an alkenyl bromide with a longer methylene run lengt h is shown in Figure 4 5. The s ynthesis includes self metathesis of 11 bromo undec 1 ene 4 6 in the presence of first generation Grubb`s metathesis catalyst and subsequent hydro genation of unsaturated dibromide 4 21 with Wilkinson`s catalyst to give s 1,20 d ibromoeicosane 4 22 Figure 4 5 Successful s ynthesis of alkenyl bromide 20 b romo eicos 1 ene 4 23 For dehydrohalogenation of alkyl d ibromide 4 22 1.5 equivalence of t BuOK suppress ed (but did not eliminate entirely) the formation of the di elimination product 4 24 T he crude mixture contained the desired alkenyl bromide, 20 bromoicos 1 ene 4 23 the di elimination product and unreacte d starting mate rial, all having close retention factors by TLC. Due to the similar polarities of these three species and the r elatively low room temperature solubility of the crude mixture in hexane a special purification procedure is followed The crude mixture was first dissolved in toluene and mixed with small amount of silica gel to form a slurry. Toluene was slowly evaporated and the

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57 resulting silica particles with adsorbed crude mixture were added to a freshly packed c olumn to form a uniform layer us ing hexane Then, a nother uniform layer of pristine silica gel was added on t op of the crude layer. Hexane was slowly added to the column without disturbing either layer The f low rate of the column was also adjusted to obtain the most efficient separation After two column chromatography passes, the desired alkenyl bromide 4 23 was recovered in moderate yield (42%). Figure 4 6. Synthesis of 21 alkyl hentetraconta 1, 40 dienes ( 4 27 a m ) Alkylation of various primary nitri le s with 11 bromo undec 1 ene (structure 4 6 in Figure 4 2) proceeded efficiently to give the corresponding monomers with different branches in high overall yields. The efficiency of alkylation with a longer alkenyl bromide (in this case 20 bromoicos 1 ene 4 23 ) was first examined with hexanenitrile 4 25e using t he previously reported procedure 156 but, mostly mono alkylated nitrile was recovered in every trial The melting point of alkenyl bromide 4 23 (T m =32 o C) limits the use of cannula wires and syringes to maintain the an hydrous conditions necessary for the correct s toichiometric ratio of lithium diisopropyl amine (LDA) to alkyl bromide during

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58 the addition of alkylating agent. The di alkylated nitrile 2 butyl 2 (ico s 19 enyl)docos 21 enenitrile, 4 26e was purified from th e mono alkylated adduct via consecutive column chromatographic separations The f ormation of mono alkylated nitrile and the multi step purification resulted in yields as low as 19%. In order to increase the yield, the alkylation procedure was modified by u se of a reaction tube to fulfill the anhydrous conditions. This modification enabled nearly quantitative di alkylation of the nitrile without formation of the mono alkylated adduct (yield = 98%). Only one column separation was then adequate to purify compo und 4 26e Decyanation of nitrile 4 26e was achieved with potassium metal via radical chemistry. The resulting terti ary radical after decyanation was quenched by abstraction of hydrogen from t BuOH to give diene monomer 4 27e in high yield This two s tep alkylation/decyanation route was employed to generate monomers having branches from methyl to pentadecyl 4 27 (a m) in moderate to high yields. 4.2 Polymer Synthesis and Primary Structure Characterization Monomers 4 27 a m were condensed to form the cor responding unsaturated ADMET polymers (Figure 4 7) Because of the relatively high melt viscosity of the resulting polymers ( 4 28 a m ), t he polymerization temperature was set to 8 5 o C At that elevated temperature Ru based catalysts are prone to have low tur nover numbers and to generate Ru H species 159 161 which would cause isomerization problems and disrupt the symmetrical nature of the monomer 162,163 Therefore, monomers 4 27 a m were condensed to form unsaturated ADMET polymer s using Schrocks` [Mo] catalyst for clean metathesis chemistry. Due to the oxophilic nature of [Mo] catalyst s all the manipulations prior to polymerization and catalyst addition (catalyst to monomer rati o 1:500) were performed in a glove box. Polymerization was initiated by melting the

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59 monomer at 50 o C an d the temperature was set to 85 o C to be able to stir the viscous polymer melt. Figure 4 7 Synthesis of precision poly mers possessing a branch on every 39th carbon. After 24 hours of reaction the polymer was cooled to RT another portion of [Mo] catalyst ( catalyst to monomer ratio 1:500 ) was added in the glove box and the temperature was set back to 85 o C ADMET polymeri zation proceeded smoothly to give the desired unsaturated linear polymers 4 28a m with no detectable side reactions. Disappearance of terminal olefin signals in 1 H NMR spectra (Figure 4 8 ) proved the complete conversion, which is necessary for any step gro wth polymerization Unsaturated polymers ( 4 28a m ) were hydrogenated using Wilkinson`s catalyst

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60 (catalyst to monomer ratio 1:250) to yield the precision polyethylenes (polymers 4 29 a m ) possessing branches from methyl to pentadecyl on every 39 th carbon Figure 4 8. A ) 1 H 500 MHz NMR spectra of monomer ( 4 27 h ), unsaturated ( 4 28h ) and saturated ( 4 29h ) pol ymers. B ) olefinic region shown in higher magnification. The p olymeriza tion and hydrogenation steps were followed with 1 H NMR spectroscopy. As an example Figure 4 8 illustrates the 1 H N MR spectra of hexyl branched polymer, 4 29h and its precursors. ADMET p olymerization of monomer 4 27h yield ed the unsaturated polymer 4 28h Formation of the ADMET polymer resulted in l oss of the terminal olefin signals ( 5.0 and 5.8 ppm) and the appearance of the internal olefin at 5.4 ppm ( Figure 4 8 ). Exhaustive hydrogenation of the internal olefins with

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61 Wilkinson`s catalyst generated 4 29h corresponding to polyethylene with hexyl branches on every 39 th carbon with com plete loss of the olefinic signals on 1 H NMR Figure 4 9. 1 3 C 126 MHz NMR spectra of monomer ( 4 27h ), unsaturated ( 4 28h ) and saturated ( 4 29h ) polymers. Polymerization and hydrogenation of monomer 4 27 h was also monitored with 13 C NMR spectroscopy (Figu re 4 9) Comparison of the 13 C NMR spectra for the monomer 4 27 h and unsaturated polymer 4 28h indicates the disappearance of the signals belonging to the terminal olefin at 114.31 and 139.44 ppm and formation of the new internal olefin ( cis olefin at 130. 12 ppm, minor product and trans olefin at 130.58 ppm, major product ) generated by the metathesis chemistry H ydrogenation of the internal olefin with Wilkinson`s catalyst yielded the saturated polymer 4 29h with no detectable trace of olefins. Infrared (I R) spectroscopy was also used to monitor this

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62 transformation (Figure 4 10) Disappearance of the out of plane C H bend absorption at 969 cm 1 indicates the complete absence of C=C in the polymer backbone and proves the full conversion for the hydrogenation step Figure 4 10 Infrared spectra for the precisely branched p olymers 4 29a (methyl) 4 29b (ethyl) 4 29c (propyl) 4 29d ( iso propyl) 4 29e (butyl) 4 29f ( iso butyl) 4 29g (pentyl) 4 29h (hexyl) 4 29i (heptyl) 4 29j (octyl) 4 29k (nonyl) 4 2 9l (decyl) 4 29m (pentadecyl) and ADMET PE After hydrogenation, sol utions of saturated polymers were co ncentrated and precipitated into methanol. It is important to note that the solubility characteristics of polymers 4 29 a m (soluble in toluene, dichlor obenzene, trichlorobenzene, etc. at high temperatures) are similar to those of polyethylenes prepared by chain polymeriz ation. Molecular weight data were obtained using high temperature gel permeation chromatography ( GPC ) in 1,2,4 trichlorobenzene at 135 o C relative to polystyrene standards. Table 4 1 illustrates the weight average molecular weights for the precisely branched unsaturated and saturated polymer s

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63 Table 4 1 Molecular weights and thermal data for precisel y branched polymers a ( kg/mol ) (PDI b ) Branch identity on every 39 th carbon T m ( o C) (peak) H m (J /g) Unsaturated Saturated No branch 134 204 70.2 ( 2.7 ) 70.2 (2. 7 ) Methyl 92 137 33.7 (2.2) 92.7 (2.0) Ethyl 76 93 56.7 (2.2) 53.1 (2.4) Propyl 78 71 217 (3.1) 225 (3.0) iso propyl 77 74 107 (2.0) 144 (3.5) Butyl 75 66 60.2 (2.3) 66.5 (2.5) is o butyl 73 51 22.6 (2.5) 54.8 (2.4) Pentyl 74 88 29.3 (2.2) 30.2 (2.0) Hexyl 73 85 30.5 (2.3) 30.5 (1.9) Heptyl 74 85 76.6 (3.0) 74.2 (2.9) Octyl 74 73 200 (3.6) 181 (3.3) Nonyl 73 84 35.9 (2.4) 34.3 (2.2) Decyl 71 76 28.0 (2.4) 27.7 (1.8) Pentadecy l 70 83 58.0 (2.4) 55.9 (2.4) a Molecular weight data were collected by GPC in 1,2,4 trichlorobenzene at 135 o C relative to polystyrene standards. b PDI, polydispersity index / 4.3 Primary Structure Ch aracterization of Precisely Branched Polymers Control over the primary structure of the final precision polymer is governed by the precision established on the molecular level. The purity of the monomers and the absence of any side reactions during the pol ymerization ensure the successful po lycondensation chemistry and level of control. Upon close inspection of the 13 C NMR data for the polymers it can be concluded that the branches are precisely placed along the polyethylene main backbone with no ne of the un desired branches due to chain transfer typically observed during chain growth chemistry. Figure s 4 11, 4 13 & 4 14 show a portion (10 55 ppm) of the 13 C NMR spectra for precise polymers having branches from methyl to octyl All spectra are dominated by a singlet at 29.99 ppm corresponding to methylenes on the main polyeth ylene chain. Note that the presence of

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64 alkyl branches precisely placed along the main chain affects the chemical shifts of carbons located within three CH 2 units from an individual branch 114 Figure 4 11. Co mparison of 13 C NMR spectra for precision polymers A ) 4 29a (methyl) B ) 4 29b (ethyl) and C ) 4 29c (propyl)

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65 To demonstrate the effect of branch identity on 13 C NMR che mical shifts in a consistent manner nomenclature defined by Randall 164 is used (Figure 4 12). Methylene carbons along the backbone of a polymer chain are identified by a p air of Greek letters to indicate the distance to branches. Carbons on the branch are identified by i B n terminal methyl length of the branch. Figure 4 12. Commonly accepted nomenclature used to identify the positions of different carbons. In the spectrum for 4 29a (methyl) which is polyethylene containing methyl branches on every 39 th backbone carbon ( F igure 4 11 A ), the resonances belonging to the methyl branch, ` ( 19.84 ppm), as well as main chain carbons + ( 37.45 ppm), + ( 27.98 ppm), + + + (29.99 ppm) and the carbon at the branch point ( 33 12 ppm) indicates that only methyl branches are present in good agreement with previously reported 114 experimen tal data and predicted values 165 Introduction of ethyl br anch es changes the chemical shifts of both backbone and side chain carbons (Figure 4 11B) The t erminal methyl carbon (1B 2 ) is now more shielded by the presence of a methylene unit, which results in a predictable shift to upfield (11.19 ppm). On the other

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66 hand, the methine carbon is deshielded with more elect ron delocalization and shifts downfield (39.41 ppm) compared to the methyl branched polymer. All the chemical shifts shown in Figure 4 11B for the polymer 4 29b (ethyl) are in good agreement with previo usly reported ethylene/1 butene and hydrogenated polybutadiene systems 86,166 168 Figure 4 13 Comparison of 13 C NMR spectra for precision polymers A ) 4 29d ( iso propyl) B ) 4 29f ( iso butyl) and C ) 4 29g (pentyl)

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67 In the spectrum for 4 29d (propyl) (Figure 4 11C) the resonances belonging to the propyl branch, ` ( 14.55 ppm), ` (20.20 ppm), ` (36.66 ppm) + ( 34.25 ppm), + ( 27. 16 ppm), + (30. 49 + + (29.99 ppm) and the methine carbon ( 37.70 ppm) indicate that only propyl branches are present in good agreement with previously reported data on chain growth polymers obtained by copolymerization of ethylene with 1 pentene 169 171 Figure 4 14. Comparison of 13 C NMR spectra for precision polymers A ) 4 29h ( hexyl ) B ) 4 29i ( hepty l ) and C ) 4 29j ( octyl )

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68 It is also interesting to compare the propyl branched polymer with the iso propyl branched isomer The 13 C NMR spectrum of polymer 4 29d ( iso propyl) is presented in Figure 4 13A. Both terminal methyl carbons on the iso propyl bran ch and the methine carbon are deshielded compared to the propyl branch to give 19.37 and 44.23 ppm, respectively. Starting from the pentyl branched polymer 4 29g (pentyl) all the longer linear branched precision polymers display very similar spectra l patt ern s with slight differences as shown in Figures 4 13C and 4 14. 4. 4 Experimental Section 4. 4 .1 Instrumentation All 1 H NMR ( 3 00 MHz) and 13 C NMR ( 75 MHz) spectra of starting materials, intermediates and monomers were recorded in CDCl 3 For polymer characte rization, 1 H NMR ( 5 00 MHz) and 13 C NMR ( 126 MHz) instrumentation were used and spectra were recorded in either CDCl 3 or C 6 D 6 Chemical sh ifts were referenced to signals from CDCl 3 (7.24 ppm for 1 H, 77.23 ppm for 13 C) with 0.03% v/v TMS and from C 6 D 6 (7.16 ppm for 1 H, 128. 39 ppm for 13 C) as an internal reference, and the temperature was maintained at either 25 or 6 5 o C. High Resolution Mass S pectrometry (HRMS) was carried out using a n Agilent 6210 TOF MS mass spectrometer in the D irect Analysis in Real Time ( DART) mode with an IonSense DART Source. Thin layer chromatography (TLC) was used to monitor all reactions and was performed on glass plates coated with silica gel (250 m thickness). C olumn chromatography was performed using ultrapure silica gel (40 63 m 60 pore size). Gel Permeation C hromatography (GPC) was performed using an Alliance GPC 2000 with an internal differential Refractive Index D etector ( RID ), internal differential viscosity detector (DP), and a p recision angle light scattering detector ( LS) at the Max

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69 Planck Institute for Polymer Research, Mainz, Germany The light scattering signal was collected at a 15 angle, and the three in line detectors were operated in series in the order LS DRI DP. The chromatography was performed at 135 C using a PLgel MIXED B column (10 m PD, 8.0 mm ID, 300 mm total length) with HPLC grade 1,2,4 trichlorobenzene as the mobile phase at a flow rate of 1.0 mL/min. Injections were made at 0.05 0.07% w/v sample concentration using a 322.5 L injection volume. In the case of universal calibration, retention times were calibrated versus narrow range molecular weight polystyrene standards (purchased from Polymer Standard Service PSS in Mainz, Germany). IR data were obtained using a Perkin Elmer Spectrum One FTIR equippe d with a LiTaO 3 detector. The unsaturated polymer sample was prepared by solution casting a thin film from toluene onto a KBr salt plate and the hydrogenated polymer sample was prepared by solution casting a thin film from boiling toluene onto a KBr salt p late. 4. 4 .2 Materials Chemicals were purchased from the Aldrich Chemical Co. and used as received unless otherwise noted. Grubb ` s first generation catalyst, bis(tricyclohexylphosphine)benzylidineruthenium( IV) dichloride, was kindly provided by Materia, Inc Schrock`s molybdenum metathesis catalyst, [(CF 3 ) 2 CH 3 CO] 2 (N 2,6 C 6 H 3 i Pr 2 )Mo=CHC(CH 3 ) 2 Ph, and W rhodium hydrogenation catalyst RhCl(PPh 3 ) 3 were purchased from Strem Chemical Ruthenium and Molybdenum catalysts were stored in an argon filled g lovebox prior to use. Tetrahydrofuran (THF) and toluene were freshly obtained from Butler Polymer Research Laboratories anhydrous solvent preparation unit. HPLC grade 1,2,4 trichlorobenzene was purchased from the Applichem GmbH. All the nitrile s and alkeny l bromide starting materials, as well as

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70 hexamethylphosphoramide and diisopropyl amine were distilled over CaH 2 All reactions were carried out in flame dried glassware under argon unless otherwise stated. 4. 4 .3 Procedures Synth esis of 11 Bromo undec 1 en e (4 6 ) A solution of 11 undecen 1 ol, 4 20 (34.11g, 0.20 mol) and CBr 4 (73.45 g, 0.22 mol) in CH 2 Cl 2 (120 mL ) was prepared in a 500 mL round bottomed flask and cooled to 0 o C. Triphenyl phosphine (58g, 0.22 mol) was added in small portions over a period of 20 minutes. An exothermic reaction occurre d, which was left stirring at 0 o C for 1hr and 40 min, then at RT for 2 hours. The crude product was filtered over a silica column, and the solution was concentrated by evap oration, until a white precipitate form ed. The liquid was poured into 400 mL of hexane with stirring and more solid (triphenylphosphine oxide, O=PPh 3 ) precipitated. The solution was decanted leaving the solid in the flask, and the h exane solution was concentrated to obtain more precipitate The solid was filtrated, and the hexane solution was evaporated to obtain 81.65 g of yellow liquid, which was fractionally distilled under reduced pressure (6 torr) to remove the bromoform, the by product. Compound 2 (4 1.9 g ) was collected as a colorless liqu id. (Yield= 90 %) The 1 H NMR spectrum was consistent with the published spectrum 172 Synthesis of 1,20 dibromo eicos 10 ene ( 4 21 ) In a 50 mL round bottomed flask 11 bromo undec 1 ene, 4 6 (50g, 0.215mol) was mixed with 0.310g 3.76 10 4 mmol, of Grubbs 1 st generation catalyst at RT (22 o C) and warmed to 45 o C for reaction under argon. It was left at 45 o C under Ar for 28 hr and finally under vacuum (7 torr) for 24 hr. The re action was quenched with 5 mL ethyl vinyl ether and dissolved in 100 mL toluene. The tol uene solution was concentrated and then poured into 1.0 L cold methanol. The methanol mixture was left in the refrigerator overnight, a nd white crystals were obtained.

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71 After vacuum filtration 15 g of a crys talline material was obtained (Yield = 80 %) The 1 H NMR spectrum was consistent with the published spectrum 172 Synthesis of 1,20 Dibromoeicosane (4 22 ) Compound 4 21 1,20 dibromo eicos 10 ene (10. 691g, 24.44 mmol) was dissolved in 90 mL degassed toluene, placed in a Parr bomb with 1.1 mg, 1.89 10 3 mmol W ilkinson `s catalyst and left to react at 55 o C under 900 psi of h ydrogen for 4 days. P urification of the product by column chromatography with toluene afforded 10.30 g of a white solid. (Yield = 96 %) The 1 H NMR spectrum was consistent with the published sp ectrum 172 Synt hesis of 20 Bromo eicos 1 ene (4 23 ) In a 250 mL round bottomed flask compound 4 22 (10.30 g, 23.4 mmol) was dissolved in 2:1 THF/toluene mixture producing a 1 M solution. The mixture was cooled using an ice water bath, and potassium tert butox ide (3.92g, 35.1 mmol) was added in small portions over 30 min. After addition, the reaction turned clou dy and was allowed to stir at 0 o C for 1 h. The reaction was quenched using water (25 mL), followed by 1 M HCl (25 mL). The organic layer was extracted a nd washed with 1M HCl (15 mL), saturated Na 2 CO 3 (15 mL), and 15 mL of water, followed by drying with magnesium sulfate. The s olvents were evaporated and the crude pr oduct was further purified by column chromatograhy using hexane as the eluent. C ompound 4 2 3 (4.85 g) was collecte d as a white solid. (Yield= 42 %) The 1 H NMR spectrum was consistent with the published spectrum 172 Synthesis of 2 methyl 2 ( e icos 19 en 1 yl)docos 21 enenitrile ( 4 26 a) Into a 100 mL 3 neck round bottomed flask equipped with a stir bar, THF (5 ml) was added and cooled to 78 o C under nitrogen. D iisopropyl amine (0.6 mL) and 2.0 mL of 2.0 M n BuLi (freshly titrated) were added and warmed to 0 o C to prepare lithium diisopropyl amine

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72 (LDA) solution in situ. The LDA solution was coole d to 78 o C and propionitrile 4 25a (0.090 mL, 1.29 mmol) was added The mixture was allowed to return to RT and was stirred for 30 minutes at RT. Separately, 20 bromo eicos 1 ene 4 23 (1.171 g, 3.26 mmol) was added to a 50 mL flame dried schlenk flask and kept u nder high vacuum prior to use at 50 o C the LDA solution was transf erred to the S chlenk flask at 78 o C and the resulting mixture was slowly warmed to 0 o C and stirred for 12 hours at that temperature. The reaction was quenched with addition of diethyl ether (40 mL) and water (10 mL). The organic phase was extracted three times with ether (3x 30 mL), washed with brine, and dried over MgSO 4 (s). The s olvents were evaporated and the crude product was further purified by column chromato grahy using toluene/hexane as the eluent Because of the very similar retardation factors between mono and di alkylated nitriles, the toluene/hexane concentration w as varied during the separation (toluene co ncentration was increased from 5 % to 30 % in 5% increments for each 250 mL po rtion of eluent.) After purification, 0.861 g of compound 4 26a was collected as white crystals (Yield = 86%) The following spectral properties were observed; 1 H NMR CDCl 3 ppm 0.92 (s, 3H), 1.14 1.52 (br, 68 H), 2.05 (td, J 1 =7.64 Hz, J 2 =6.51 Hz, 4 H ), 4.85 5.09 (m, 4 H), 5.66 5.95 (m, 2 H) ; 13 C NMR (CDCl 3 18.10, 24 22, 24.98, 29.18, 29.44, 29.69, 29.82, 29.93, 30.07, 34.02, 36.82, 36.95 39.62, 114.25 (vinyl CH 2 ), 126.34 ( CN), 139.46 (vinyl CH); EI/HRMS: [M] + calculated for C 43 H 81 N : 61 1.6364 found: 611 6314 Elemental analysis calculated for C 43 H 81 N: 84.37 C, 13.37 H 2.29 N; found: 84.24 C, 13.65 H 2.38 N. Synthesis of 2 ethyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 b) The same procedure described above for the synthesis of comp ound 4 26 a was followed. After

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73 purification, 0.439 g of compound 4 26 b was collected as white crystals (Yield= 86%). The following spectral properties were observed; 1 H NMR CDCl 3 ppm 1.00 (t, J=7.36 Hz, 3H), 1.18 1.44 (br, 70 H), 2.04 (td, J 1 =7.65 Hz, J 2 =6.51 Hz, 4 H), 4.87 5.08 (m, 4 H), 5.69 6.11 (m, 2 H) ; 13 C NMR (CDCl 3 24.53, 24 93, 29.14, 29.40, 29.69, 29.82, 29.95, 33.96, 34.09, 35.77, 41.33 114.29 (vinyl CH 2 ), 124.51 ( CN), 139.52 (vinyl CH); EI/HRMS: [M] + calculated for C 44 H 83 N : 626.6598 found: 626.6611 Elemental analysis calculated for C 44 H 83 N: 84.40 C, 13.36 H 2.22 N; found: 83.53 C, 13.23 H 2.22 N. Synthesis of 2 propyl 2 (icos 19 e n 1 yl)docos 21 enenitrile ( 4 26 c) The same procedure described above for the synthesis of compound 4 26 a was followed. After purification, 0.543 g of compound 4 26 c was collected as white crystals (Yield = 73%). The following spectral properties were obs erved; 1 H NMR CDCl 3 ppm 0.96 (t, J =6.79 Hz, 3 H), 1.19 1.45 (br, 72 H), 2.05 (td, J 1 =7.63 Hz, J 2 =6.50 Hz, 4 H), 4.88 5.07 (m, 4 H), 5.72 5.94 (m, 2 H) ; 13 C NMR (CDCl 3 14.42, 15.80, 16.63, 24.50, 29.19, 29.33, 29.88, 30.02, 34.02, 34.16, 36.37, 40.79, 114.24 (vinyl CH 2 ), 124.74 ( CN), 139.51 (vinyl CH); EI/HRMS: [M] + calculated for C 45 H 85 N : 640.9755 found: 640.6762 Elemental analysis calculated for C 45 H 85 N: 84.43 C, 13.38 H 2.19 N; found: 84.58 C, 13.19 H 2.20 N. Synthesis of 2 iso pro pyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 d) The same procedure described above for the synthesis of compound 4 26 a was followed. After purification, 0.569 g of compound 4 26 d was collected as white crystals (Yield = 83%). The following spectral pro perties were observed; 1 H NMR CDCl 3 ppm 1.02 (d, J =6.80 Hz, 6 H), 1.16 1.44 (br, 72 H), 2.06 (td, J 1 =7.64 Hz, J 2 =6.52 Hz, 4 H), 4.88 5.07

PAGE 74

74 (m, 4 H), 5.73 5.92 (m, 2 H); 1 3 C NMR (CDCl 3 14.45, 15.66, 16.64, 24.50, 29.21, 29.35, 29.90, 30.02 34.04, 34.13, 35.63, 41.10, 114.29 (vinyl CH 2 ), 124.48 ( CN), 139.52 (vinyl CH); EI/HRMS: [M] + calculated for C 45 H 85 N : 640.6755 found: 640.6777 Elemental analysis calculated for C 45 H 85 N: 84.43 C, 13.38 H 2.19 N; found: 84.21 C, 13.24 H 2.16 N. Synthe sis of 2 iso butyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 f) The same procedure described above for the synthesis of compound 4 26 a was followed. After purification, 0.435 g of compound 4.26 f was collected as white crystals (Yield = 56%). The followi ng spectral properties were observed ; 1 H NMR CDCl 3 ppm 1.07 (d, J =6.79 Hz, 6 H), 1.13 1.48 (s, 74 H), 2.04 (td, J 1 =7.65 Hz, J 2 =6.50 Hz, 4 H), 4.88 5.09 (m, 4 H), 5.73 5.92 (m, 2 H) ; 13 C NMR (CDCl 3 23.27, 23.31, 25.51, 25.62, 26.71, 29.13, 29.35, 29.68, 29.79, 30.01, 30.34, 30.45, 34.07, 35.06, 35.17, 44.07, 44.18, 114.24 (vinyl CH 2 ), 124.73 ( CN), 139.50 (vinyl CH); EI/HRMS: [M] + calculated for C 46 H 87 N : 654.6911 found: 654.6911 Elemental analysis calculated for C 46 H 87 N: 84.45 C, 13.40 H 2.14 N; found: 84.47 C, 13.32 H 2.17 N. Synthesis of 2 butyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 e) The same procedure described above for the synthesis of compound 4 26 a was followed. After purification, 0.435 g of compound 4 26 e was collected as white crystals (Yield = 85%). The following spectral properties were observed ; 1 H NMR (CDCl 3 J=6.79, 3H), 1.20 1.35 (m, 74H), 2.05 (td, J 1 =7.63 Hz, J 2 =6.51 Hz, 4 H), 4.91 5.04 (m, 4H), 5.78 5.87 (m, 2H) ; 13 C NMR (CDCl 3 4, 23.11, 24.49, 26.66, 29.18, 29.39, 29.58, 29.66, 29.74, 29.85, 29.92, 34.05, 36.33, 40.83, 114.29 (vinyl CH 2 ), 129.92 ( CN), 139.50 (vinyl CH); EI/HRMS: [M] + calculated for C 46 H 87 N: 653.6839,

PAGE 75

75 found: 653.6917. Elemental analysis calculated for C 46 H 87 N: 8 4.45 C, 13.40 H, 2.14 N; found: 84.47 C, 13.38 H, 2.17 N. Synthesis of 2 pentyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 g) The same procedure described above for t he synthesis of compound 4 26 a was followed. After purification, 0.435 g of compound 4 2 6 g was collected as white crystals (Yield = 42%). The following spectral properties were observed ; 1 H NMR CDCl 3 ppm 0.91 (t, J =6.80 Hz, 3 H), 1.14 1.47 (m, 76 H), 2.05 (td, J 1 =7.64 Hz, J 2 =6.51 Hz, 4 H), 4.86 5.08 (m, 4 H), 5.72 5.92 (m, 2 H) ; 13 C NMR (CDCl 3 14.23, 22.64, 24.11, 24.25, 24.51, 26.52, 29.05, 29.19, 29.32, 29.59, 29.72, 29.99, 32.12, 33.99, 36.26, 40.80, 114.25 (vinyl CH 2 ), 124.80 ( CN), 139.49 (vinyl CH); EI/HRMS: [M] + calculated for C 47 H 89 N : 668.7068 found: 668.7098 Ele mental analysis calculated for C 47 H 89 N: 84.48 C, 13.42 H 2.10 N; found: 84.66 C, 13.32 H 2.23 N. Synthesis of 2 hexyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 h) The same procedure described above for the synthesis of compound 4 26 a was followed. Aft er purification, 0.581 g of compound 4 26 h was collected as white crystals (Yield = 70%). The following spectral properties were observed ; 1 H NMR CDCl 3 ppm 0.88 (t, J=6.79, 3 H), 1.10 1.45 (br, 78 H), 2.04 (td, J 1 =7.63 Hz, J 2 =6.51 Hz, 4 H), 4.85 5.08 (m, 4 H), 5.68 5.95 (m, 2 H) ; 13 C NMR (CDCl 3 14.40, 22.87, 22.99, 26.57, 26.69, 26.93, 29.08, 29.20, 29.44, 29.68, 29.79, 29.91, 30.39, 32.66, 33.85, 33.97, 34.09, 37.55, 37.67, 114.30 (vinyl CH 2 ), 124.80 ( CN), 139.48 (vinyl CH); EI/HRMS: [M] + calculated for C 48 H 91 N : 682.7224 found: 682.7241 Elemental analysis calculated for C 48 H 91 N: 84.50 C, 13.44 H 2.05 N; found: 84.53 C, 13.4 5 H 2.19 N.

PAGE 76

76 Synthesis of 2 heptyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 i) The same procedure described above for the synthesis of compound 4 26 a was followed. After purification, 0.581 g of compound 4 26 i was collected as white crystals (Yield = 3 8%). The following spectral properties were observed ; 1 H NMR ppm 0.87 (t, J =6.80 Hz, 3 H), 1.06 1.43 (m, 80 H), 2.05 (td, J 1 =7.60 Hz, J 2 =6.54 Hz, 4 H), 4.86 5.08 (m, 4 H), 5.72 5.93 (m, 2 H) ; 13 C NMR (CDCl 3 14.83, 20.06, 20.46, 20.60, 26. 89, 29.17, 29.31, 29.44, 29.71, 29.84, 29.98, 30.38, 32.79, 33.86, 34.00, 37.35, 37.48, 49.41, 114.26 (vinyl CH 2 ), 124.31 ( CN), 139.45 (vinyl CH); EI/HRMS: [M] + calculated for C 49 H 93 N : 696.7381 found: 696.7402 Elemental analysis calculated for C 49 H 93 N: 84.53 C, 13.46 H 2.01 N; found: 83.65 C, 13.40 H 1.98 N. Synthesis of 2 octyl 2 (icos 19 en 1 yl)docos 21 enenitrile (4 26j) The same procedure described above for the synthesis of compound 4 26 a was followed. After purification, 0.581 g of compound 4 2 6 j was collected as white crystals (Yield = 95%). The following spectral properties were observed; 1 H NMR ppm 0.88 (t, J =6.79 Hz, 3 H), 1.11 1.41 (m, 82 H), 2.06 (td, J 1 =7.64 Hz, J 2 =6.49 Hz, 4 H), 4.88 5.11 (m, 4 H), 5.74 5.98 (m, 2 H); 13 C NMR (CD Cl 3 29.15, 29.44, 29.48, 29.71, 29.94, 29.92, 30.33, 32.88, 33.97, 37.40, 48.44, 114.30 (vinyl CH 2 ), 124.34 ( CN), 139.50 (vinyl CH); EI/HRMS: [M] + calculated for C 50 H 95 N: 710.7537, found: 710.7554. Elemental an alysis calculated for C 50 H 95 N: 84.55 C, 13.48 H, 1.97 N; found: 84.54 C, 13.42 H, 2.06 N. Synthesis of dodecanenitrile (4 25k) In a flame dried 250 ml three neck round bottomed flask equipped with reflux condenser and stir bar, 1 bromodecane (10.89 g, 49. 25 mmol) was added and dissolved in 35 mL of anhydrous DMF. Sodium cyanide

PAGE 77

77 ( 3.088 g, 63.00 mmol ) was dissolved in 50 m L anhydrous DMF and added to the 1 bromodecane solution in one portion under Ar flow. The r eaction mixture was stirred for 24 hours at 65 o C and then quenched with 100 mL DI water. The o rganic phase was extracted with Et 2 O (3x50 mL ) and dried over MgSO 4 The c rude product was filtered, concentrated and further purified via column chromatography with hexane/EtOAc 9/1 as eluent to give dodeca nenitrile (5.29 g, 31.64 mmol) as a colorless oil (Yield = 64%). The following spectral properties were observed; 1 H NMR ( CDCl 3 ppm 0.87 (t, J =6.80 Hz, 3 H), 1.26 (br. s., 12 H), 1.37 1.51 (m, 2 H), 1.56 1.72 (m, 2 H), 2.32 (t, J =7.08 Hz, 2 H); 13 C NMR (CDCl 3 ) ppm 14.04, 17.05, 22.64, 25.37, 28.63, 28.75, 29.25, 29.30, 29.45, 31.84, 119.76 ( CN); EI/HRMS: [M+NH 4 ] + calcula ted for C 12 H 23 N: 185.2012, found: 185.2018. Elemental analysis calculated for C 12 H 23 N: 78.97 C, 12.65 H, 8.37 N; found: 79.03 C, 12.74 H, 8.30 N. Synthesis of 2 nonyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 k) The same procedure described above for th e synthesis of compound 4 26 a w as followed using the dodecanenitrile synthesiz ed from 1 bromodecane. After purification, 0.659 g of compound 4 26 k was collected as white crystals (Yield = 78%). The following spectral properties were observed; 1 H NMR ppm 0.89 (t, J =6.80 Hz, 3 H), 1.14 1.47 (m, 84 H), 2.04 (td, J 1 =7.62 Hz, J 2 =6.56 Hz, 4 H), 4.86 5.08 (m, 4 H), 5.71 5.94 (m, 2 H); 13 C NMR (CDCl 3 29.61, 29.80, 29.97, 32.16, 33.92, 36.28, 40.84, 114.24 (vinyl CH 2 ), 124.81 ( CN), 139.50 (vinyl CH); EI/HRMS: [M] + calculated for C 51 H 97 N: 724.7694, found: 724.7710. Elemental analysis calculated for C 51 H 97 N: 84.57 C, 13.50 H, 1.93 N; found: 84.75 C, 13.61 H, 1.98 N.

PAGE 78

78 Synthesis of 2 decyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 l) The same procedure described above for the synthesis of compound 4 26 a was followed. After purification, 0.553 g of compound 4 26 l was collected as white crystals (Yield = 56%). The following spectral p roperties were observed; 1 H NMR ( CDCl 3 ppm 0.91 (t, J =6.79 Hz, 3 H), 1.12 1.45 (m, 86 H), 2.06 (td, J 1 =7.63 Hz, J 2 =6.58 Hz, 4 H), 4.84 5.06 (m, 4 H), 5.72 5.95 (m, 2 H); 13 C NMR (CDCl 3 26.52, 29.04, 29 .20, 29.35, 29.63, 29.84, 29.94, 32.18, 33.94, 36.28, 40.85, 114.25 (vinyl CH 2 ), 124.80 ( CN), 139.49 (vinyl CH); EI/HRMS: [M] + calculated for C 52 H 99 N: 738.7850, found: 738.7881. Elemental analysis calculated for C 52 H 99 N: 84.59 C, 13.51 H, 1.90 N; found: 8 4.82 C, 13.60 H, 2.00 N. Synthesis of 2 pentadecyl 2 (icos 19 en 1 yl)docos 21 enenitrile ( 4 26 m) The same procedure described above for the synthesis of compound 7a was followed. After purification, 0.737 g of compound 7m was collected as white crystals (Yield = 65%). The following spectral properties were observed; 1 H NMR ( CDCl 3 ppm 0.90 (d, J =6.79 Hz, 3 H), 1.10 1.46 (m, 96 H), 2.05 (td, J 1 =7.61 Hz, J 2 =6.51 Hz, 4 H), 4.85 5.09 (m, 4 H), 5.75 5.90 (m, 2 H); 13 C NMR (CDCl 3 ): ppm 14.34, 22.92, 2 6.93, 29.18, 29.39, 29.59, 29.74, 29.85, 29.90, 29.94, 30.38, 32.16, 33.92, 34.05, 37.61, 114.28 (vinyl CH 2 ), 124.79 ( CN), 139.49 (vinyl CH); EI/HRMS: [M] + calculated for C 57 H 109 N: 808.8639, found: 808.8655. Elemental analysis calculated for C 57 H 109 N: 84 .68 C, 13.59 H, 1.73 N; found: 84.81 C, 13.33 H, 1.82 N. Synthesis of 21 methylhentetraconta 1,40 diene ( 4 27 a) Potassium metal (0.45 g, 11.5 mmol), HMPA (0.9 mL, 6.76 mmol), and diethyl ether (20 mL) were transferred to a 100 mL 3 necked round bottomed f lask equipped with a stir bar, addition funnel,

PAGE 79

79 diolefin 4 26 a (0.861 g, 1.34 mmol) and t BuOH (0.6 mL, 10.38 mmol) in diethyl ether (20 mL) was added dropwise to the reactor at 0 o C The reaction mi xture was warmed to RT and stirred for 25 hours. The reaction was quenched with isopropanol (20 mL), extracted three times with diethyl ether (3x50 mL), washed with brine (50 mL) and dried over MgSO 4 The solution was filtered, concentrated by rotary evapo ration and purified by column chromatograhy using hexane as the eluent. Compound 4 27a was collected as white crystals (0.659 g, 1.12 mmol). (Yield= 84%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.84 (d, J =6.20 Hz, 3 H), 1.27 (br, 68 H), 2.05 (td, J 1 =7.64 Hz, J 2 =6.51 Hz, 4 H), 4.83 5.10 (m, 4 H), 5.71 5.94 (m, 2 H) 13 C NMR (CDCl 3 ): ppm 19.95, 27.31, 29.18, 29.39, 29.74, 29.85, 29.93, 30.26, 34.05, 37.32, 114.28 (vinyl CH 2 ), 139.51 (vin yl CH). Elemental analysis calculated for C 42 H 82 : 85.92 C, 14.08 H; found: 85.78 C, 14.24 H. Synthesis of 21 ethylhentetraconta 1,40 diene ( 4 27 b) The same procedure described above for the synthesis of compound 4 27 a was followed. After purification, 0.5 19 g of compound 4 27 b was collected as white crystals (Yield = 95%) The following spectral properties were observed; 1 H NMR (C DCl 3 ) ; ppm 0.90 (t, J =6.80 Hz, 3 H), 1.05 1.45 (m, 70 H), 2.04 (td, J 1 =7.65 Hz, J 2 =6.51 Hz, 4 H), 4.84 5.09 (m, 4 H), 5.74 5.90 (m, 2 H) 13 C NMR (CDCl 3 ): ppm 14.36, 22.96, 26.61, 26.93, 29.19, 29.39, 29.75, 29.86, 29.90, 29.94, 30.39, 32.63, 33.89, 33.9 2, 34.05, 37.63, 114.28 (vinyl CH 2 ), 139.49 (vinyl CH). Elemental analysis calculated for C 43 H 84 : 85.92 C, 14.08 H; found: 86.08 C, 14.09 H. Synthesis of 21 propylhentetraconta 1,40 diene ( 4 27 c) The same procedure described above for the synthesis of com pound 4 27 a was followed. After purification,

PAGE 80

80 0.349 g of compound 4 27 c was collected as white crystals (Yield = 76%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.96 (t, J =6.80 Hz, 3 H), 1.27 (s, 34 H), 2.05 (td, J 1 =7.63 Hz, J 2 =6.50 Hz, 4 H), 4.83 5.10 (m, 4 H), 5.70 5.94 (m, 2 H) 13 C NMR (CDCl 3 ) ppm 14.47, 17.90, 24.50, 29.18, 29.38, 29.66, 29.74, 29.85, 29.92, 34.05, 36.36, 40.86, 114.28 (vinyl CH 2 ), 139.49 (vinyl CH). Elemental analysis calculated for C 44 H 86 : 85.91 C, 14.09 H; found: 86.04 C, 14.10 H. Synthesis of 21 iso propylhentetraconta 1,40 diene ( 4 27 d) The same procedure described above for the synthesis of compound 4 27 a was followed. After purification, 0.473 g of compound 4 27 d was collected as white crystals (Yield = 82%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.82 (d, J =6.50 Hz, 6 H), 1.27 (s, 72 H), 2.06 (td, J 1 =7.64 Hz, J 2 =6.52 Hz, 4 H), 4.80 5.13 (m, 4 H), 5.71 5.95 (m, 2 H) 13 C NMR ( CDCl 3 ppm 19.43, 27.99, 29.18, 29.39, 29.74, 29.94, 30.41, 30.75, 34.05, 43.91, 114.28 (vinyl CH 2 ), 139.51 (vinyl CH). Elemental analysis calculated for C 44 H 86 : 85.91 C, 14.09 H; found: 86.11 C, 14.18 H. Synthesis of 21 butylhentetraconta 1,40 diene ( 4 27 e) The same procedure described above for the synthesis of compound 4 27 a was followed. After purification, 0.229 g of compound 4 27 e was collected as white crystals (Yield = 98%) The following spectral properties were observed; 1 H NMR (CDCl 3 1.41 (br, 74H), 2.05 (td, J 1 =7.63 Hz, J 2 =6.51 Hz, 4 H), 4.91 5.04 (m, 4H), 5.78 5.87 (m, 2H) ; 13 C NMR (CDCl 3 29.98, 30.43, 33.65, 33.96, 37.64, 114.31 (vinyl CH 2 ), 139.45 (vinyl CH); Elemental analysis calculated for C 45 H 88 : 85.90 C, 14.10 H; found: 85.93 C, 14.06 H.

PAGE 81

81 Synthesis of 21 iso butylhentetraconta 1,40 diene ( 4 27 f) The same procedure described above for the synthesis of compound 4 27 a was fol lowed. After purification, 0.329 g of compound 4 27 f was collected as white crystals (Yield = 71%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.86 (d, J =6.51 Hz, 6 H), 1.27 (s, 74 H), 2.04 (td, J 1 =7.65 Hz, J 2 =6.50 Hz, 4 H), 4.85 5.11 (m, 4 H), 5.70 5.94 (m, 2 H); 13 C NMR ( CDCl 3 ) ppm 23.23, 25.53, 26.70, 29.18, 29.40, 29.75, 29.86, 29.94, 30.41, 34.05, 34.10, 35.13, 44.11, 114.29 (vin yl CH 2 ), 139.49 (vinyl CH). Elemental analysis calculated for C 45 H 88 : 85.90 C, 14.10 H; found: 86.17 C, 14.02 H. Synthesis of 21 pentylhentetraconta 1,40 diene ( 4 27 g) The same procedure described above for the synthesis of compound 4 27 a was followed. Af ter purification, 0.265 g of compound 4 27 g was collected as white crystals (Yield = 85%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.91 (t, J =6.79 Hz, 3 H), 1.14 1.47 (m, 76 H), 2.05 (td, J 1 =7.64 Hz, J 2 =6.51 Hz, 4 H), 4.86 5.08 (m, 4 H), 5.72 5.92 (m, 2 H); 13 C NMR (C DCl 3 ) ppm 14.36, 22.95, 26.60, 26.92, 29.18, 29.39, 29.74, 29.85, 29.94, 30.38, 32.62, 33.91, 34.05, 37.6 2, 114.28 (vinyl CH 2 ), 139.49 (vinyl CH). Elemental analysis calculated for C 45 H 88 : 85.90 C, 14.10 H; found: 86.00 C, 14.04 H. Synthesis of 21 hexylhentetraconta 1,40 diene ( 4 27 h) The same procedure described above for the synthesis of compound 4 27 a was followed. After purification, 0.416 g of compound 4 27 h was collected as white crystals (Yield = 88%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.89 (t, J =6.80 Hz, 3 H), 1.27 (br, 78 H), 2.04 (td, J 1 =7.63 Hz, J 2 =6.51 Hz, 4 H), 4.87 5.07 (m, 4 H), 5.74 5.91 (m, 2 H); 13 C NMR (C DCl 3 ppm 14.35, 22.94, 26.92, 29.18, 29.39, 29.74, 29.85, 29.90, 29.93, 30.06, 30.38, 32.19, 33.92, 33.94, 34. 05, 37.62, 114.28 (vinyl CH 2 ),

PAGE 82

82 139.49 (vinyl CH). Elemental analysis calculated for C 46 H 90 : 85.89 C, 14.11 H; found: 86.00 C, 14.17 H. Synthesis of 21 heptylhentetraconta 1,40 diene ( 4 27 i) The same procedure described above for the synthesis of compound 4 27 a was follow ed. After purification, 0.262 g of compound 4 27 i was collected as white crystals (Yield = 93%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.88 (t, J =6.80 Hz, 3 H), 1.26 (br, 80 H), 2.05 (td, J 1 =7.60 Hz, J 2 =6.54 Hz, 4 H), 4.85 5.09 (m, 4 H), 5.70 5.91 (m, 2 H); 13 C NMR ( CDCl 3 ppm 14.35, 22.93, 26.93, 29.18, 29.39, 29.62, 29.74, 29.85, 29.94, 30.38, 32.17, 33.92, 34.05, 37.62, 114 .28 (vinyl CH 2 ), 139.50 (vinyl CH). Elemental analysis calculated for C 48 H 94 : 85.89 C, 14.11 H; found: 85.63 C, 14.25 H. Synthesis of 21 octylhentetraconta 1,40 diene ( 4 27 j) The same procedure described above for the synthesis of compound 4 27 a was follo wed. After purification, 0.452 g of compound 4 27 j was collected as white crystals (Yield = 85%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.89 (t, J =6.80 Hz, 3 H), 1.27 (br, 82 H), 2.06 (td, J 1 =7.64 Hz, J 2 =6.49 Hz, 4 H), 4.82 5.12 (m, 4 H), 5.69 6.00 (m, 2 H); 13 C NMR ( CDCl 3 ppm 14.35, 22.92, 26.92, 29.18, 29.38, 29.60, 29.74, 29.85, 29.94, 30.38, 32.16, 33.92, 34.05, 37.61, 114 .29 (vinyl CH 2 ), 139.51 (vinyl CH). Elemental analysis calculated for C 49 H 96 : 85.88 C, 14.12 H; found: 85.84 C, 13.98 H. Synthesis of 21 nonylhentetraconta 1,40 diene ( 4 27 k) The same procedure described above for the synthesis of compound 4 27 a was follo wed. After purification, 0.452 g of compound 4 27 k was collected as white crystals (Yield = 85%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.89 (t, J =6.80 Hz, 3 H), 1.04 1.45 (br, 84 H), 2.04 (td, J 1 =7.62 Hz, J 2 =6.56 Hz, 4 H), 4.86 5.07 (m, 3 H), 5.73

PAGE 83

83 5.91 (m, 1 H); 13 C NMR ( CDCl 3 ppm 14.35, 22.92, 26.93, 29.19, 29.39, 29.60, 29.74, 29.85, 29.90, 29.94, 30.38, 32.16, 33.92, 34. 05, 37.62, 114.28 (vinyl CH 2 ), 139.50 (vinyl CH). Elemental analysis calculated for C 50 H 98 : 85.87 C, 14.13 H; found: 85.79 C, 14.20 H. Synthesis of 21 decylhentetraconta 1,40 diene ( 4 27 l) The same procedure described above for the synthesis of compound 4 27 a was followe d. After purification, 0.425 g of compound 4 27 l was collected as white crystals (Yield = 84%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.88 (t, J =6.80 Hz, 3 H), 1.27 (br, 86 H), 2.06 (td, J 1 =7.63 Hz, J 2 =6.58 Hz, 4 H), 4.83 5.10 (m, 4 H), 5.70 5.95 (m, 2 H); 13 C NMR ( CDCl 3 ppm 14.36, 22.93, 26.93, 29.19, 29.40, 29.60, 29.75, 29.86, 29.94, 30.39, 32.16, 33.92, 34.06, 37.61, 114 .29 (vinyl CH 2 ), 139.50 (vinyl CH). Elemental analysis calculated for C 51 H 100 : 85.87 C, 14.13 H; found: 85.64 C, 14.27 H. Synthesis of 21 pentadecylhentetraconta 1,40 diene ( 4 27 m) The same procedure described above for the synthesis of compound 4 27 a was followed. After purification, 0.437 g of compound 4 27 m was collected as white crystals (Yield = 90%) The following spectral properties were observed; 1 H NMR ( CDCl 3 ) ppm 0.87 (t, J =6.80 Hz, 3 H), 1.27 (br, 96 H), 2.05 (td, J 1 =7.61 Hz, J 2 =6.51 Hz, 4 H), 4.86 5.07 (m, 4 H), 5.73 5.91 (m, 2 H); 13 C NMR ( CDCl 3 ppm 14.34, 22.92, 26.93, 29.18, 29.39, 29.59, 29.74, 29.85, 29.90, 29.94, 30.38, 32.16, 33.92, 34.05, 37. 61, 114.28 (vinyl CH 2 ), 139.49 (vinyl CH). Elemental analysis calculated for C 56 H 110 : 85.85 C, 14.15 H; found: 85.72 C, 14.22 H. Polymerization of 21 methylhentetraconta 1,40 diene ( 4 28 a) Monomer 4 27 a (0.335 g, 0.57 mmol) was placed in a 25 ml flame dri ed S chlenk tube under Ar and

PAGE 84

84 heated to 75 o C using an oil bath and high vacuum (10 5 torr). After 2 hours of stirring at these conditions, the monomer was cool ed to room temperature and the S chlenk tube was placed into the glove box. Schrock catalyst, ( 0.9 mg, 1.17 x 10 3 mmol ; catalyst to monomer ratio = 1:500) was added, the S chlenk tube was removed from t he glove box and connected to high vacuum. Polymerization was initiat ed by melting the monomer at 50 o C an d the temperature was set to 85 o C to enable sti r ring of the viscous polymer melt. After 24 hours, the polymer was cooled to RT and another 0.9 mg portion of Schrock catalyst was added in the glove box After 24 hours, the S chlenk tube was opened to air and the polymer was diss olved in 5 mL of toluene. The p olyme r solution was poured into acidic methanol to precipitate the polymer The p olymer was filtered, re di ssolved and re precipitated two more times to remove the traces of catalyst. Compound 4 28a ( 0.295 g ) was recovered as a white solid (yield=92 % ) The following spectral properties were observed; 1 H NMR (300 MHz, C 6 D 6 ) ppm 0.97 (d, J =6.20 Hz, 3 H), 1.38 (br, 68 H), 1.96 2.24 (m, 4 H), 5.38 5.64 (m, 2 H); 13 C NMR (75 MHz, C 6 D 6 ) ppm 26.06, 27.97, 29.99, 30.54, 30.90, 33.43, 33.67, 37.18, 38.00, 131.16. Polymerization of 21 ethylhentetraconta 1,40 diene ( 4 28 b) Th e same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.320 g of compound 4 28 b was collected (Yield = 87%) The following spectral properties were observed; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.89 (t, J =6.80 Hz, 3 H), 1.06 1.44 (br, 70 H), 1.88 2.09 (m, 4 H), 5.28 5.46 (m, 2 H); 13 C NMR (126 MHz, CDCl 3 ) ppm 14.36, 22.96, 26.61, 26.94, 27.44, 29.42, 29.56, 29.77, 29.8, 29.90, 29.95, 30.01, 30.40, 32.63, 32.84, 33.88, 33.93, 37.63, 130.11, 130.57.

PAGE 85

85 Polymerizat ion of 21 propylhentetraconta 1,40 diene ( 4 28 c) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.320 g of compound 4 28 c was collected (Yield = 92%) The following spectral properties were observed; 1 H NMR (299 MHz, CDCl 3 ) ppm 0.89 (t, J =6.20 Hz, 3 H), 1.27 (br, 72 H), 1.85 2.14 (m, 4 H), 5.28 5.51 (m, 2 H); 13 C NMR (75 MHz, CDCl 3 ) ppm 14.79, 20.05, 26.93, 29.42, 29.78, 29.95, 30.41, 32.84, 33.93, 36.35, 37.41, 130.57. Polymerization of 21 iso propylhentetraconta 1,4 0 diene ( 4 28 d) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.320 g of compound 4 28 d was collected (Yield = 90%) The following spectral properties were observed; 1 H NMR (299 MHz, CDCl 3 ) ppm 0. 81 (d, J =6.50 Hz, 6 H), 1.26 (br, 70 H), 1.85 2.11 (m, 4 H), 5.28 5.48 (m, 2 H); 13 C NMR (75 MHz, CDCl 3 ) ppm 19.43, 28.00, 29.42, 29.78, 29.95, 30.42, 30.75, 32.84, 43.92, 130.58. Polymerization of 21 butylhentetraconta 1,40 diene ( 4 28 e) The same p rocedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.270 g of compound 4 28 e was collected (Yield = 90%) The following spectral properties were observed; 1 H NMR (299 MHz, CDCl 3 ) ppm 0.90 (t, J =6.80 Hz, 3 H), 1.0 1 1.49 (br, 74 H), 1.86 2.13 (m, 4 H), 5.25 5.47 (m, 2 H); 13 C NMR (75 MHz, CDCl 3 ) ppm 14.40, 23.40, 26.94, 29.41, 29.77, 29.95, 30.40, 32.84, 33.93, 37.60, 130.57. Polymerization of 21 iso butylhentetraconta 1,40 diene ( 4 28 f) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.270 g of compound 4 28 f was collected (Yield = 83%) The following

PAGE 86

86 spectral properties were observed; 1 H NMR (299 MHz, CDCl 3 ) ppm 0.86 (d, J =6.50 Hz, 6 H), 1.27 (br, 74 H), 1.85 2.13 (m, 4 H), 5.25 5.50 (m, 2 H); 13 C NMR (75 MHz, CDCl 3 ) ppm 23.23, 25.53, 26.71, 29.41, 29.56, 29.78, 29.95, 30.41, 32.84, 34.11, 35.13, 44.10, 130.11, 130.57. Polymerization of 21 pentylhentetraconta 1,40 diene ( 4 28 g) The same procedu re described above for the synthesis of polymer 4 28 a was followed. After purification, 0.298 g of compound 4 28 g was collected (Yield = 89%) The following spectral properties were observed; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.83 (t, J =6.80 Hz, 3 H), 1.27 (br, 7 6 H), 1.86 2.10 (m, 4 H), 5.27 5.48 (m, 2 H); 13 C NMR (126 MHz, CDCl 3 ) ppm 11.11, 26.13, 26.98, 27.44, 29.42, 29.56, 29.77, 29.81, 29.90, 29.95, 30.40, 32.84, 33.45, 39.09, 130.12, 130.58. Polymerization of 21 hexylhentetraconta 1,40 diene ( 4 28 h) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.233 g of compound 4 28 h was collected (Yield = 84%) The following spectral properties were observed; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.89 (t, J =6.80 Hz, 3 H), 1.03 1.46 (br, 78 H), 1.85 2.10 (m, 4 H), 5.29 5.48 (m, 2 H); 13 C NMR (126 MHz, CDCl 3 ) ppm 14.38, 22.97, 26.94, 26.97, 27.47, 29.44, 29.59, 29.81, 29.84, 29.93, 29.98, 30.10, 30.43, 32.19, 32.22, 32.87, 33.96, 37.66, 130.14, 130.60. Polymerizat ion of 21 heptylhentetraconta 1,40 diene ( 4 28 i) The s ame procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.165 g of compound 4 28 i was collected (Yield = 88%) The following spectral properties were observed; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.88 (t, J =6.80 Hz, 3 H), 1.26 (br, 80 H), 1.87 2.10 (m, 4 H), 5.26 5.47 (m, 2 H); 13 C NMR (126 MHz,

PAGE 87

87 CDCl 3 ) ppm 14.35, 22.93, 26.94, 27.45, 29.42, 29.56, 29.63, 29.78, 29.90, 29.96, 30.36, 30.40, 32.18, 32.84, 33.94, 37.63, 130.11, 130.57. Poly merization of 21 octylhentetraconta 1,40 diene ( 4 28 j) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.232 g of compound 4 28 j was collected (Yield = 90%) The following spectral properties were obs erved; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.91 (t, J =6.80 Hz, 3 H), 1.29 (br, 82 H), 1.88 2.13 (m, 4 H), 5.28 5.50 (m, 2 H); 13 C NMR (126 MHz, CDCl 3 ) ppm 14.24, 22.92, 27.10, 27.53, 29.46, 29.60, 29.80, 29.92, 29.98, 30.43, 32.20, 32.84, 34.21, 37.87, 130.16, 130.64. Polymerization of 21 nonylhentetraconta 1,40 diene ( 4 28 k) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.330 g of compound 4 28 k was collected (Yield = 90%) The following spectral properties were observed; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.89 (t, J =6.80 Hz, 3 H), 1.27 (br, 84 H), 1.88 2.15 (m, 4 H), 5.29 5.52 (m, 2 H); 13 C NMR (75 MHz, CDCl 3 ) ppm 14.37, 22.96, 26.61, 26.94, 29.42, 29.78, 29.95, 30.40, 32.63, 32.84, 33.93, 37.63, 130.11, 130.58. Polymerization of 21 decylhentetr aconta 1,40 diene ( 4 28 l) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.272 g of compound 4 28 l was collected (Yield = 71%) The following spectral properties were observed; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.90 (t, J =6.80 Hz, 3 H), 1.02 1.46 (br, 86 H), 1.87 2.11 (m, 4 H), 5.25 5.49 (m, 2 H); 13 C NMR (126 MHz, CDCl 3 ) ppm 14.35, 22.93, 26.94, 27.44, 29.42, 29.56, 29.60, 29.78, 29.90, 29.96, 30.39, 32.16, 32.84, 33.94, 37.62, 130.11, 130.57.

PAGE 88

88 Poly merization of 21 pentadecylhentetraconta 1,40 diene ( 4 28 m) The same procedure described above for the synthesis of polymer 4 28 a was followed. After purification, 0.296 g of compound 4 28 m was collected (Yield = 86%) The following spectral properties wer e observed; 1 H NMR (500 MHz, CDCl 3 ) ppm 0.88 (t, J =6.80 Hz, 3 H), 1.27 (br, 96 H), 1.87 2.10 (m, 4 H), 5.29 5.49 (m, 2 H); 13 C NMR (126 MHz, CDCl 3 ) ppm 14.35, 22.92, 26.94, 29.42, 29.60, 29.78, 29.90, 29.96, 30.40, 32.16, 32.85, 33.94, 37.62, 130.10, 130.57. Hydrogenation of methyl b ranched polymer ( 4 29 a) In a 125 mL Parr bomb glass sleeve, unsaturated polymer 4 28 a (0.2 52 g) was dissolved in 40 mL degassed toluene. Wilkinson`s hydrogenation catalyst (0.7 mg, 7.610 4 mmol ; ca talyst to monomer ratio 1:250) was added and the bomb was charged with 900 psi of hydrogen. The reaction was allowed to proceed for three days at 90 o C. The polymer solution w as concentrated and poured in to acidic methanol and the resulting precipitate was then filtered and dissolved in 5 mL toluene. The polymer was re di ssolved and re precipitated two more times to remove the traces of catalyst. Polymer 4 29a ( 0.177 g ) was collected as a white solid (yield=70%). The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.96 (d, J =6.20 Hz, 3 H ), 1.17 1.56 (br, 74 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 19.84, 27.42, 29.99, 30.34, 33.12, 37.34. Hydrogenation of ethyl branched polymer (4 29 b) The same procedure described above for the synthesis of saturated polymer 4 29 a was followed. After purifica tion, 0.273 g of polymer 4 29 b was collected (Yield = 96%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.90 (t, J =6.80 Hz, 3 H), 1.28 (br, 76 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 11.19, 26.44, 27.16, 29.99, 30.46, 33.76, 39.4 1.

PAGE 89

89 Hydrogenation of propyl branched polymer (4 29 c) The same procedure described above for the synthesis of saturated polymer 4 29 a was followed. After purification, 0.200 g of polymer 4 29 c was collected (Yield = 96%) The following spectral properties we re observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.95 (t, J =6.80 Hz, 3 H), 1.38 (s, 78 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 14.55, 20.20, 27.16, 29.99, 30.49, 34.25, 36.66, 37.70. Hydrogenation of iso propyl branched polymer (4 29 d) The same procedure described above for the synthesis of saturated po lymer 4 29 a was followed. After purification, 0.302 g of polymer 4 29 d was collected (Yield = 93%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.93 (d, J =6.50 Hz, 6 H), 1.38 (br, 78 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 19.37, 28.20, 29.84, 29.99, 30.48, 31.14, 44.23. Hydrogenation of butyl branched polymer ( 4 29 e) The same procedure from the synthesis of saturated polymer 4 29 a was followed. After the purification, 0.302 g of polymer 4 29 e were collected (Yield = 93%) The fo llowing spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.92 (t, J =6.80 Hz, 3 H), 1.29 (br, 80 H) ; 13 C NMR (126 MHz, C 6 D 6 ) ppm 14.28, 22.68, 26.80, 29.99 30.45, 32.75, 34.27, 37.88 Hydrogenation of iso butyl branched polymer (4 29 f) The same procedure described above for the synthesis of saturated po lymer 4 29 a was followed. After purification, 0.037 g of polymer 4 29 f was collected (Yield = 28%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 1.07 (d, J =6.59 Hz, 6 H), 1.37 1.61 (br, 80 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 23.09, 25.75, 26.95, 29.99, 30.49, 34.49, 35.56, 44.43.

PAGE 90

90 Hydrogenation of pentyl branched polymer (4 29 g) The same procedure described above for the synthesis of saturated polymer 4 29 a was followed. After purification, 0.141 g of polymer 4 29 g was collec ted (Yield = 85%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.91 (t, J =6.80 Hz, 3 H), 1.29 (s, 82 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 14.29, 22.96, 26.77, 27.12, 29.99, 30.46, 32.47, 32.71, 34.24, 37.91. Hydrogenation of hexyl branched polymer (4 29 h) The same procedure described above for the synthesis of sat urated polymer 4 29 a was followed. After purification, 0.205 g of polymer 4 29 h was collected (Yield = 85%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.91 (t, J =6.80 Hz, 3 H), 1.29 (br, 84 H) ; 13 C NMR (126 MHz, C 6 D 6 ) p pm 14.27, 22.92, 27.09, 27.12, 29.99, 30.09, 30.56, 32.24, 34.23, 37.90. Hydrogenation of heptyl branched polymer (4 29 i) The same procedure described above for the synthesis of saturated polymer 4 29 a was followed. After purification, 0.205 g of polymer 4 29 i was collected (Yield = 85%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 1.05 (t, J =6.80 Hz, 3 H), 1.49 (br. s., 86 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 14.27, 22.88, 27.12, 27.18, 29.63, 29.99, 30.04, 30.45, 30.48, 32.17, 34.28, 37.97. Hydrogenation of octyl branched polymer (4 29 j) The same procedure described above for t he synthesis of saturated polymer 4 29 a was followed. After purification, 0.186 g of polymer 4 29 i was collected (Yield = 89%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.91 (t, J =6.80 Hz, 3 H), 1.36 (br. s.,

PAGE 91

91 75 H); 13 C NMR (126 MHz, C 6 D 6 ) ppm 14.04, 22.86, 27.14, 27.17, 29.60, 29.94, 29.99, 30.04, 30.33, 30.47, 32.14, 34.18, 37.96 Hydrogenation of nonyl branched polymer (4 29 k) The same procedure described above for the synthesis of saturated polymer 4 29 a was follow ed. After purification, 0.263 g of polymer 4 29 k was collected (Yield = 88%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.90 (t, J =6.80 Hz, 3 H), 1.28 (br, 89 H) ; 13 C NMR (126 MHz, C 6 D 6 ) ppm 14.26, 22.94, 27.03, 27.07, 29.99, 30.09, 30.48, 30.51, 32.23, 34.11, 37.97 Hydrogenation of decyl branched polymer (4 29 l) The same procedure described above for the synthesis of saturated polymer 4 29 a was followed. After purification, 0.263 g of polymer 4 29 l was collected (Yiel d = 88%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.91 (t, J =6.80 Hz, 3 H), 1.28 (br, 92 H) ; 13 C NMR (126 MHz, C 6 D 6 ) ppm 14.24, 22.85, 27.08, 27.15, 29.59, 29.99, 30.07, 30.48, 30.51, 32.12, 34.31, 37.89 Hydrogenation of pentadecyl branched polymer (4 29 m) The same procedure described above for t he synthesis of saturated polymer 4 29 a was followed. After the purification, 0.215 g of polymer 4 29 k was collected (Yield = 86%) The following spectral properties were observed; 1 H NMR (500 MHz, C 6 D 6 ) ppm 0.88 (t, J =6.80 Hz, 3 H), 1.28 (s, 83 H); 13 C N MR (126 MHz, C 6 D 6 ) ppm 14.35, 22.84, 27.15, 27.21, 29.59, 29.99, 30.01, 30.42, 30.45, 32.23, 34.31, 37.93.

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92 CHAPTER 5 CH A RACTERIZATION OF PRECISION POLYETH YLENE WITH BRANCH ES ON EVERY 39 TH CARBON 3 5.1 Thermal Behavior of Precisely Branched Polymers Ther olefin copolymers is mainly influenced by short chain branching (SCB) and SCB distribution 108,152 Variou s studies have been verified the effect of SCB and SCB distributi on on the ultimate thermal properties of copolymers 98,173 177 Figure 5 1. Differential scanning calorimetry thermograms for 2nd heating cycles of (top to bottom) ADMET PE 4 29a (methyl) 4 29b (ethyl) 4 29c (p ropyl) 4 29 d (iso propyl) 4 29e (butyl) and 4 29 f (iso butyl) with groups precisely placed on every 39 th carbon. Heating rate= 10 o C/min The limited control over the primary structure of such chain growth copolymers results in heterogeneous SCB distribut ion and hampers the interpretation of the thermal data. The precision polymers described here present a quite different picture Because 3 Part of this chapter is adapted with permission from (Zuluaga, F.; Inci B.; Nozue, Y.; Hosoda, S.; Wagener, K. B. Macromolecules 2009 42, 4953). Copyright (2009) American Chemical Society.

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93 the distanc e between the branches is set at the monomer level, the branch identity can be systematically changed to exa mine the effect of individual branches on properties. Figures 5 1 and 5 2 present the DSC thermograms of linear ADMET PE and precise polymers having branches from methyl to pentadecyl increasing both length and bulkiness Figure 5 2 Differential scannin g calorimetry thermograms for 2 nd heating cycles of precision polymers 4 29g (pentyl) 4 29h (hexyl) 4 29i (heptyl) 4 29j (octyl) 4 29k (nonyl) and 4 29l (decyl) and 4 29m (pentadecyl) with groups precisely placed on every 39 th carbon. Heating rate=10 o C /min It is immediately obvious that m ethyl branching significantly r educes the melt ing point of ADMET polyethylene : O n the other hand, all further branches, from ethyl to pentadecyl produce polymers that have very similar (in some cases identical) m eltin g point s As discussed further below, this behavior may be attributed to a change in morphology from a situation where the methyl cell, to one where branches of greater mass are excluded from the unit cell. It is

PAGE 94

94 i mportant to note that the ethyl branch is included in the unit cell when the branch is placed on every 21 st carbon 158 Increasing the distance between two consecutive branches from 20 carbons (10.0 mole% branch ) to 38 carbons (5.26 mole% branch ) expels the ethyl branches from the crystal lattice in to the amorphous phase. Similar observations were also reported for commercial ethylene/1 butene and hydrogenated polybutadiene systems where the ethyl branch is mostl y found in the amorphous region 84,178,179 Figure 5 3. Dependence of branch identity on melting point and heat of fusion As shown in Figure 5 3, u nbranched ADMET polyethylene displays thermal behavior virtually t he same as that of high density polyethylene (T m =134 o H m =204 J /g). Incorporation of methyl branches precisely placed on every 39 th carbon, polymer 4 29 a (methyl) disrupts the crystal structure and decrease s the melting temperature to 92 o C and the entha lpy of fusion to 137 J/g. A similar trend is observed when the branch

PAGE 95

95 is an ethyl group, 4 29 b (ethyl) : T he melting point decreases below that of 4 29 a (methyl) ( T m = 76 H m = 93 J/g ). Depression of both the melting temperature and th e heat of fusion show s that the disruption of the crystal structure is even greater with the presence of the larger ethyl defects. However, e xtension of the branch size from ethyl to propyl 4 29 c (propyl) does not lead to further decreases (T m =78 H m = 71 J/g ) Similar behavior is observed f or precision polyethylene possessing longer branches. These homologous polymers with long branches also display sharp well defined endothermic transitions Overall, the thermal be havior of precision polymers is con olefin analogs in which t he methyl branch is included in the unit cell and the branches equal to and larger than an ethyl group are excluded. Figure 5 4. C omparison of the thermal behavior of the precisi on polymer 4 29e (butyl) and ethylene/1 hexene copolymer prepared via chain polymerization with a metallocene catalyst. Both profiles are the 2 nd heating c urves with a heating rate of 10 o C/min. Similar to previously reported 114,116,158 alkyl branched precision polymers, ADMET PE and polymers 4 29a m show narrow and well defined melting endotherms,

PAGE 96

96 with none of the broadening observed for analogous copolymers obtained via chain polymerization 152,180,181 Figure 5 4 compares t he thermal behavior of precision polymer 4 29e (butyl) 182 to that of a copolymer of ethylene and 1 hexene having the same net concentration of butyl branches along th e polymer backbone (although not regularly spaced) prepared via chain polymerization with a metallocene catalyst The m etallocene copolymer displa ys a higher melting point (98.9 o C) tha n the precision ADMET polymer (75.3 o C) and shows a broader melting trans ition (Figure 5 4) 5.2 Determination of Morphology and Crystal Structure o f Precision Polymers 5.2.1 IR Spectroscopy In addition to primary structure determination, IR spectroscopy can also be used to delineate the morphological picture of polyolefins 183 IR absorption band regions at 710 740 cm 1 and 1450 1480 cm 1 corresponding to the CH 2 rocking and scissor modes, respectively are known to be very sensitive to the crystal packing behavior of polyethylene 183 The presence o f the orthorhombic unit cel l structure is demonstrated by the cha racteristic Davydov splitting of these absorption bands due to strong intermolecular interactions within the individual polymer chains, whereas no splitting occurs for the metastable triclini c, monoclinic or hexagonal crystal structures 183 Figure 5 5 illustrates CH 2 rocking and scissor band regions of the precisely branched thirteen polymers 4 29 a m and ADMET PE The o rthorhombic crystal structure of ADMET PE is evidenced by two distinct signals at 1462 cm 1 and 1472 cm 1 for the CH 2 rocking band, 718 cm 1 and 730 cm 1 for CH 2 scissor band. The same splitting pattern is observed for precision polymers 4 29 a (methyl) 4 29 c (propyl) 4 29 e (butyl) and 4 29 k (nonyl) The other precisely branched polymers display single

PAGE 97

97 absorption bands for the rocking and scissor regions, indicating the absence of the orthorhombic crystal behavior as previously reported for precision polymers with shorter branch spacing 114,116,158 Figure 5 5 The CH 2 rocking and scissors band regions for the precisely branched p olymers 4 29a (methyl) 4 29b (ethyl) 4 29c (propyl) 4 29d ( iso propyl) 4 29e (butyl) 4 29f ( iso butyl) 4 29g (pentyl) 4 29h (hexyl) 4 29i (heptyl) 4 29j (octyl) 4 29k (nonyl) 4 29l (decyl) 4 29m (pentadecyl) and ADMET PE All the polymers were analyzed as prepared without any thermal treatment. Tashiro et al carried out a temperature dependent study to investigate the orthorhombic t o hexagonal pha se transition in crystals of ultradrawn high modulus polyethylene samples subjected to high ten sile stress 183 and demonstrated the change in the rocking band region as a function of the temperatu re. As the temperature reaches close to the melting point of polyethylene, the intensity of the orthorhombic absorption peaks (1471 cm 1 and 1462 cm 1 ) gradually decreases and a new peak appears at 1466

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98 cm 1 corresponding to the hexagonal crystal structure 183 The s ingle peak s at 1466 cm 1 for precision polymers 4 29 b (ethyl) 4 29 d ( iso propyl) 4 29 f ( iso butyl) 4 29 g (pentyl) 4 29h (hexyl ) 4 29 i (heptyl) 4 29 j (octyl) 4 29l (decyl) and 4 29 m (pentadecyl) suggests the formation of a metastable crystalline phase (usu ally observed at high temperature and pressure conditions for high density polyethylene) at room temperature. Room temperature stabilization of this highly disordered phase is a direct result of the branch being present. 5.2.2 Solid State 13 C NMR Solid Sta te 13 C NMR spectroscopy is a powerful techni que to demonstrate the detailed structure and molecular motions for various solid polymers 184 186 The phase structure of the amorphous, the amorphous crystalline interfac ial, and the crystalline phases for semi crystalline polymers can be verified by examining 13 C spin lattice relaxation and spin spin relaxation behavior 84,187 191 Figure 5 6 shows the 10 45 ppm region (methylene carbons) of the cross polarization (CP)/ magic angle spinning (MAS) high resolution solid state 13 C NMR spectra of precision polymers 4 29 a (methyl) 4 29 b (ethyl) 4 29 c (propyl) 4 29e (butyl) 4 29k (nonyl) and 4 29m (pentadecyl) These spectra indicate that the introduction of branches lead s to lattice distortion and local con formational disorder, where the type of crystal structure and polymer morphology is str ongly dependent on the branch identity. The first feature observed in Figure 5 6 is that the all six slowly cooled samples ha ve the isotropic chemical shift at 32.9 ppm correspond ing to crystalline methylene carbons. A s inglet at 32.9 ppm is equivalent t o the all trans crystalline methylene in ADMET PE 123 (32.8 ppm) given that the solution grown single crystal of 4 29 a (methyl)

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99 unit cell parameter (Table 5 2). Figu re 5 6 CP/MAS spectra of precision polymers 4 29a (methyl) 4 29 b (ethyl) 4 29c (propyl) 4 29e (butyl) 4 29k (nonyl) and 4 29m (pentadecyl) 13 C NMR spectra are recorded at RT Short CP contact time (1ms) was chosen to increase the intensity of the crystalline region prominently. Dashed lines represent polymer s rapidly cooled from melt at 50 o C /min while solid lines represent p olymers sl owly cooled from melt at 0.5 o C /min. In troduction of ethyl branches on every 39 th carbon disrupts the crystal structure of unbranched ADMET PE even more The small hump at 34.0 ppm in the spectrum of 4 29a (methyl) becomes a shoulder in rapidly co oled 4 29b (ethyl) For the slowly cooled 4 29b (ethyl) sample, the peak at 34.0 ppm becomes more obvious suggesting the coexi stence of two crystalline morphologies Similar peaks in the downfield region (34.1

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100 ppm) were previously reported for precision polymers having chlor ine and bromine substituents at every 19 th carbon and these were attributed to the existence of triclinic unit cell structure 123 In the case of the propyl branched polymer 4 29c (propyl) the rapidly cooled sample exhibits a broad unsymmetrical singlet at 32.9 ppm but slow cooling results in a shoulder at 34.0 pp m with much lower intensity than the 34.0 ppm r esonance for polymer 4 29b (ethyl) This suggests that 4 29c (propyl) exists in the all trans conformation A s imilar trend is observed as we incorporate the butyl branches (polymer 4 29e (butyl) ) where the peak at 34.0 ppm diminishes and the all trans co nformation of methylene units forms exclusively With this in mind it can be concluded that methyl branches are included in the crystalline lattice and that branches equal to or larger than ethyl are expelled from the lattice. However, ethyl and propyl b ranches are not large enough to be fu lly excluded from the unit cell and these branches are positioned in both the amorphous and crystalline phases. Slow cooling of polymers 4 29b (ethyl) and 4 29c (propyl) from melt provides sufficient time for the branc hes to be partially incorporated (especially for the ethyl branch) into the crystalline lattice. For the polymers possessing longer branches (nonyl and pentadecyl) the solid state 13 C NMR spectra of slowly cooled samples (the bot tom two graphs in Figure 5 6 ) show two distinct chemical shifts in the crystalline region, indicating the coexistence of two crystalline phases. Because of their branch sizes, polymers 4 29k (nonyl) and 4 29m (pentadecyl) are expected to display spectra similar to that polymer 4 29 e (butyl) with fully excluded side chains. This unexpected observation of two crystalline phases

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101 for both 4 29k (nonyl) and 4 29m (pentadecyl) is presumably due to co crystallization of the long branches with the main polymer chain. The spectra in Figure 5 6 also provide information about the amorphous phase. Amorphous carbons of polymers 4 29a (methyl) 4 29b (ethyl) 4 29c (propyl) and 4 29e (butyl) exhibit broad peaks centered at 30.8 ppm, whereas polymers 4 29k (nonyl) and 4 29m (pentadecyl) display pe aks at 30.6 and 31.0 ppm respectively. The reason for the observed differences in peak positions remains unclear but it is possible that long branches have d ifferent effect on the organization of the amorphous region. 5.2.3 Wide Angle X ray Diffraction (WAXD) W ide angle X ray diffraction (WAXD) measurements further support the observation of a change in polymer morphology as a fu nction of branch size. WAXD diffr actograms of precision polymers having branches from methyl to pentadecyl are shown in Figures 5 7 & 5 8 T hese patterns indicate that the introduction of branches lead s to lattice distortion and local con formational disorder, where the type of crystal structure and polymer morphology is strongly dependent on the branch identity. For the sake of co mparison, ADMET PE is displa yed at the bottom of Figure 5 7 It exhibits the typical orthorhombic crystal form with two characteristic crystalline peaks superimposed on the amorphous halo exactly the same as for high density polyethylene made by chain pro pagation chemistry The more intense peak at scattering angle 21.5 o and the less intense one at 24.0 o correspond to reflection planes (110) a nd (200), respectively. Introduction of precisely placed methyl branches on every 39 th carbon (polymer 4 29a (methy l) in Figure 5 7) disturbs the unit cell of ADMET PE and shifts the scattering angles to 21.1 o and 23.0 o Electron diffraction measurements

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102 for the solution grown single crystals of polymer 4 29 a (methyl) indicate the formation of the disturbed orthorhombi c unit cell with an extended a value (Table 5 2). Figure 5 7 Wide angle X ray diffraction patterns for precision polymers 4 29 a (methyl) 4 29 b (ethyl) 4 29 c (propyl) 4 29 d ( iso propyl) 4 29 e (butyl) 4 29 f ( iso butyl) and ADMET PE obtained at RT P rior to data acquisition all samples were heated to 20 o C above the melting temperature of each polymer to remove the thermal history and the n cooled to room temperature at a rate of 50 o C /min.

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103 Figure 5 8 Wide angle X ray diffraction patterns for preci sion polymers 4 29 g (pentyl ) 4 29 h (hexyl ) 4 29 i (heptyl ) 4 29 j ( octyl ) 4 29 k (nonyl ) 4 29 l ( decyl ) and 4 29m (pentadecyl) obtained at RT P rior to data acquisition, all samples were heated to 20 o C above the melting temperature of each polymer and th e n cooled to room temperature at a rate of 50 o C /min.

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104 For the polymers possessing larger branches (from ethyl to decyl), the WAXD diffractograms show nearly identical scattering patterns in which the crystalline peaks shift to 21.4 o and 23.4 o (Figures 5 7 and 5 8 ), indicating the existence of similar morphologies. Interestingly, p olymer 4 29m (pentadecyl) displays different scattering peak values (21.2 o and 23.2 o ) than polymers having branches from ethyl to decyl. Figure 5 9 Scattering angles of two s trong reflections for alkyl branched precision polymers. The blue graph is for the reflection at higher angle while the black one is for the reflection at lower angle. To better understand these observations, the scattering angles of two strong diffraction peaks are plotted as a function of branch identity in Figure 5 9 T h e decrease of scattering angles for methyl branched polymer 4 29a (methyl) indicates the larger d spacing between the diffraction planes suggesting the inclusion of the methyl branches i nto the unit cell A clear morphology change for polymers ranging from 4 29b (ethyl) to

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105 4 29l (decyl) is evidenced by th e increase of scattering angles, confirm ing the exclusion of branches from the unit cell. It is important to no te that precision polymer 4 29m (pentadecyl) exhibits a distinct morphological behavior in which the relatively lon g pentadecyl branch presumably co crystallizes with th e main polymer chain, thereby increasing the d spacing between the diffraction planes Figure 5 10 Wide angl e X ray diffraction patterns for precision polymers 4 29b ( ethyl ) 4 29c ( propyl ) 4 29e ( butyl ) and 4 29h ( hexyl ) obtained at RT P rior to data acquisition, all samples were heated to 20 o C above the melting temperature of each polymer and the n cooled to room temperature at a rate of either 1 o C /min or 50 o C /min. An interesting aspect of the WAXS profile s for most precision polymers is the appearance of the crystalline peak in the amorphous halo region (peak at 19.6) suggesting the possible co existence of metastable crystal packing. The extent of t he metastable phase formation was further investigated with temperature controlled WAXD measurements In doing so, the polymer in question was heated to 20 o C above its

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106 melting temperature and then cooled at a rat e of either 1 o C /min or 50 o C /min as shown in Figures 5 10 and 5 11 Figure 5 11 Wide angle X ray diffraction patterns for precision polymers 4 29 i ( heptyl ) 4 29 k ( nonyl ) 4 29 l (decyl) and 4 29 m (pentadecyl) obtained at RT P rior to data acquisition a ll samples were heated to 20 o C above the melting temperature of each polymer and the n cooled to room temperature at a rate of 1 o C /min or 50 o C /min. Precision polymers having branches equal to or greater in mass than butyl exhibit strong thermal history dep endence For samples cooled at 1 o C/min, these polymers show a n increase in the intensity of the peak at 19.6 o and a decrease in the intensity of the peak at 21.4 o compared to the corresponding peaks for sample cooled at 50 o C/min. T he WAXD profiles of poly mers 4 29b (ethyl) and 4 29c (propyl) display subtle thermal history dependence, but ADMET PE and 4 29a (methyl) generate virtually the same

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107 diffraction patterns for both cooling rates (not shown in Figures 5 10 & 5 11) Slow cooling extends the stabilizat ion of the metastable crystal formation especially for longer branched precision polymers. Figure 5 12. WAXD pattern of a) P recision polymer 4 29e (butyl) and b) E thylene/1 hexene copolymer prepared via chain polymerization with a metallocene catalyst. Both samples were cooled to RT from melt at 60 o C/min. In Figure 5 12, the WAXD behavior of precision polymer 4 29e (butyl) is compared to that of a copolymer of ethylene and 1 hexene having the same net concentration of butyl branches along the polymer ba ckbone but prepared via chain polymerization with a metallocene catalyst 182 Unlike the precision polymer 4 29e (butyl) metallocene ethylene/1 hexene copolymer does not exhibit a crystalline peak at

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108 the amorphous halo region. Formation of a metastable crystal phase is a direct result of the precise branch placement along the polymer backbone. Figure 5 1 3 Temperature dependent Wide angle X ray diffraction patterns for ADMET PE and methyl branched precision polyme r 4 29a ( methyl ) Both samples were heated to 20 o C above the melting temperature of each polymer and the n cooled to room temperature at a rate of 1 o C /min X ray data were collected in situ during cooling. In situ WAXD measurements for some of the precisio n polymers were employed to delineate the morphology development as the polymers were coole d from the melt (cooling rate=1 o C/min), as shown in Figures 5 1 3 and 5 1 4 ADMET PE is also displayed in Figure 5 12 exhibiting the t ypical orthorhombic crystal stru cture with two characteristic peaks at the crystallization temperature (T c =108 o C) The ADMET PE sa mple is cooled with a rate of 1 o C/min from the molten state and the amorphous halo readily transformed to a well defined orthorhombic crystalline scattering p eak pattern when the system reached the crystallization temperature. Similar to ADMET PE the precision polymer 4 29a (methyl) quickly forms the orthorhombic unit cell at its crystallization temperature (T c =85 o C).

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109 In the cas e of polymers with longer branc hes ( 4 29b (ethyl) 4 29c (propyl) and 4 29e (butyl) ), in situ WAXD measurements exhibit a significantly different morphology development motif compared to ADMET PE and 4 29a (methyl) For example, X ray diffraction peak positions of the precision polymer 4 29b (ethyl) experience an unusual shif t during the cooling experiment (Figure 5 14). Figure 5 1 4 Temperature dependent Wide angle X ray diffraction patterns for precis ion polymers 4 29b ( ethyl ) 4 29c (propyl) and 4 29e (butyl) All polymer samples w ere heated to 20 o C above the melting temperature of each polymer and the n cooled to room temperature at a rate of 1 o C /min X ray data were collected in situ during cooling.

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110 The two diffraction peaks at 20.5 o and 21.8 o appear at the crys tallization tempera ture of polymer 4 29b (ethyl) (73 o C) and shift to 19.6 o and 23.4 o respectively as the system is cooled to RT. Appearance of the 21.4 o peak at 54 o C suggests the existence of the two different crystalline morphologies. It is interesting to note that the cr ystalline phase appearing at 73 o C is metastable in nature and its unit cell dimensions continue changing even well below the crystallization temperature. This is a direct result of precise branch placement As the crystallization temperature is reached, p olymer backbone crystallization starts and the system attempts to expel the ethyl branch outside to the crystalline phase. However, the precisely placed adjacent et hyl branch temporarily enters the unit cell but it subsequently expelled back to the amorph ous phase. 4 29c (propyl) and 4 29e (butyl) 5.2.4 Transmission Electron Microscopy (TEM) The CP/MAS NMR and WAXD measurements were used to investigate melt crystallized s am ples to delineate the morphology and the crystal structure of the precision polymers. Transmission Electron Microscopy (TEM) was used to analyze the lamellar nature of solution grown polyethylene single crystals 192 1 97 The TEM images of the solution grown single crystals of ADMET PE and precision polymers are illustrated in Figure 5 1 5

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111 Figure 5 1 5 TEM images of 1) ADMET PE 2) 4 29a (methyl) 3) 4 29c (propyl) 4) 4 29d ( iso propyl) 5) 4 29e (butyl) 6) 4 29g ( pentyl) 7) 4 29h (hexyl) 8) 4 29i (heptyl) 9) 4 29j (octyl) 10) 4 29k (nonyl) 11) 4 29l (decyl) and 12) 4 29m (pentadecyl) ADMET PE and 4 29a (methyl) crystals were grown from 0.03 wt% C 2 Cl 4 solution and all the o ther polymer single crystals were gr own from 0.03% o xylene solution. Lozenge shape d rhombohedral single crystals were observed for ADMET PE and precisely branched polyethylene samples consistent with the previous reports on solution grown HDPE single crystals 195,196 The l amellae thickness of each polymer single crystal was determi ned using the previously published protocol 198 As shown in Table 5 1, methyl branching reduces the lamellae thickness of ADMET PE but all further branches, from ethyl to pentadecyl produce polymers that have very similar lamellae thicknesses.

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112 Table 5 1. Lamellae thicknesses of ADMET PE and precision polymers determined by TEM. Polymer Thickness (nm) ADMET PE 9.75 4 29a (methyl) 7.09 4 29b (ethyl) 4.79 4 29e (butyl) 4.25 4 29g (pentyl) 5.03 4 29h (hexyl) 4.17 4 29i (heptyl) 4.39 4 29j (octyl) 4.06 4 29k (nonyl) 4.67 4 29l (decyl) 4.16 4 29m (pentadecyl) 5.33 These results provide additional evidence of a clear change in morphology of these polymers from a situation where the methyl unit cell, to one where branches of greater mass are excluded from the unit cell Figure 5 16 Selected area single crystal electron diffraction patterns of ADMET PE and polymer 4 29a (methyl) Selected area single crystal electron diffraction patterns of ADMET PE and polymer 4 29a (methyl) are illustrated in Figure 5 16 Unlike the WAXD diffractograms of melt crystallized polymers, single crystal e lectron diffraction patterns provide

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113 information from higher order diffractions and give a better picture of the unit cell configuration. Calculated unit cell parameters of ADMET PE and polymer 4 29a (methyl) are presented in Table 5 2 together with previously reported data for HDPE 2 Table 5 2. Unit cell dimensions of HDPE ADMET PE and 4 29a (methyl) Polymer Unit Cell a, b, c, HDPE Orthorhombic 7.42 4.95 2.55 ADMET PE Orthorho mbic 7.48 4.98 2.55 4 29a (methyl) Orthorhombic 7.75 4.93 2.55 Introduction of precisely placed methyl branches on every 39 th carbon extends the a parameter of the orthorhombic unit cell confirming the incorporation of the m ethyl branches Figu re 5 17 Structural model for precision polymer 4 29a (methyl) Methyl branches are incorporated into the unit cell and lamellae stem length is estimated to be 54 methylene units. Figure 5 17 demonstra tes the structural model for precision polymer 4 29a (m ethyl) in which the lamellae stem length is esti mated to be 54 methylene units and three methylene units are used at the folding point

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114 5.3 Instrumentation and Sample Preparation Differential scanning calorimetry (DSC) was performed using a TA Instruments DSC Q1000 equipped with a controlled cooling accessory at a heating and cooling rate of 10 C/min unless otherwise specified. Calibrations were made using indium and freshly distilled n octane as the standards for peak temperature transitions and indium fo r the enthalpy standard. IR data were obtained using a Perkin Elmer Spectrum One FTIR outfitted with a LiTaO 3 detector. P olymer sample s were prepared by solution casting thin film s from boiling toluene onto KBr salt plate s Wide angle X ray (WAXS) powder diffraction data were collected on a Mar345 Image Pl ate Detector with plate diameter of 345 mm and outside dimensions (515 mm values ranging from 10 to 40. Each diffractogram for th e in situ WAXD measurements was collected using an accumulation time of 300 seconds The temperature control unit was attached to the sample holder and all the cooling experiments were performed at either 1 o C/min or 50 o C/ min. Solid state NMR was carried out utilizing a Bruker spectrometer equipped with a Bruker Avance II+ console working at 1 H Larmor frequency of 850 MHz. Polymer samples were tightly and evenly packed in 2.5 mm rotors and CP MAS spectra were acquired usi ng 1 ms contact time and 10 kHz MAS conditions. For TEM sam ple preparation, carbon black was evaporated under 10 3 atm onto the mica slides to form uniform carbon layer s of 5 10 nm thickness. The c arbon layer

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115 was removed with DI water and regular mesh TE M copper grids were coated by dipping them in water. One drop of polymer stock solution (0.03 wt%) was deposited onto the carbon coated copper grid and solvent was evaporated at RT under the hood. TEM images obtained on a Tecnai F20 (FEI) transmission elec tron microscope operated at an acceleration voltage of 200 kV. In order to reduce beam damage to the polymer specimen a low dose exposure protocol was applied for image acquisition. T hickness images were obtained using a FEI Tecnai F20 electron microscop e equipped with a Gatan imaging filter (GIF) and a slow scan CCD (charged coupled device) camera. The GIF system allows both parallel detection EELS and energy filtered imaging/diffraction. A CCD camera can digitally collect electron images and diffraction patterns. By coupling the CCD camera to a computer, energy filtered images could be acquired and processed in a quantitative manner. An energy window was used to select an energy range of low electrons. T aking two consecutive imag es from the same sample, one with the slit positioned at the zero loss peak and one without the slit, yields two images, the elastical filtered image I_0 and the inelastic image I_t. After aligning both images for possible sample drift, the relative thicknes s at each point of the images was given by: t/lambda = ln(I_0/I_t) in which lambda is the mean free path of the respective material for the respective electron energy (200 kV). Calculation of the mean free path scale s the image to an absolute thickness mapp ing.

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116 CHAPTER 6 SYNTH ESIS AND CH A RACTERIZATION OF PRECISION POLYETHYLE NE WITH BRANCH ES ON EVERY 75 TH CARBON 4 6 .1 Monomer Sy nt hesis As illustrated in Tab le 2 1 c ommercial LLDPEs predominantly have olefin incorporation ratios of 2 5 mole % with melting points in the range from 100 to 125 o C While the p recision po lymers described in Chapters 4 and 5 provide model systems for fundamental research, they still suffer from their relatively low melting po ints. This c h apter describes efforts to prepare precision polyethylene w ith longer ethylene run length and increased melting point. Figure 6 1. Synthetic strategy to generate alkylating agent with 36 methylene run length Increasing the run length at the monomer level requires reproducible synthesis of alkylating agent, requiring several tedious column chromatography passes for purification of long alkenyl bromides. Figure 6 1 outlines the first try synthetic strategy whi ch targeted octatriacont 37 en 1 yl 4 methylbenzenesulfonate (compound 6 9 ) to generate monomers with 36 methylene run length. 4 Part of this chapter is adapted with permission from (Inci, B.; Wagener, K. B. Journal of the American Chemical Society 20 11 133, 1 1872). Copyright (2011) American Chemical Society.

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117 In this synthetic scheme, the t osylated alcohol is preferred over the bromide as a leaving group to increase the polarity difference between compounds 6 5 and 6 6 and facilitate the column chromatographic separation. C ommercially available undec 10 en 1 ol ( 6 1 ) was tosylated with p toluenesulfonyl chloride in the presence of pyridine to yield compound 6 2 Self metathesis an d hydroge nation of alkenyl tosylate gave icosane 1,20 diyl bis(4 methylbenzenesulfonate) 6 4 in high yield. H owever, the elimination step with t BuOK to give compounds 6 5 and 6 6 was not successful While the conversion of a tosylate to the corresponding alkene is a common strategy, the elimination is usually done in two steps 199 201 Thus, the tosylates are generally converted first to the iodide and then subjected to elimination 202 From the purification viewpoint, formation of alkenyl iodide will not enhanc e the polarity difference between the mono and di elimination products. Another synthetic strategy (Figure 6 2) was followed to increase the ethylen e run length utilizing compound 6 4 In this synthetic scheme, 1.5 equivalents of a lkenyl bromide 6 10 is coupled with icosane 1,20 diyl bis(4 methylbenzenesulfonate) 6 4 to generate hentriacont 30 en 1 yl 4 methylbenzenesulfonate ( 6 11 ) Figure 6 2. Synthetic strategy to g enerate alkylating agent with 29 methylene run length. Typical Grignard conditi ons were employed with Mg at 20 o C but the desired tosylate substitution was not observed. Copper based complexes 203 206 and salts 207 are widely used in carbon carbon bond forming reactions and exhibit highly selective

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118 substitutions with alkyl and alkenyl groups with aryl halides or tosylates. The effect s of the copper species on the Grignard coupling reaction were examined and the results are presented in Table 6 1. Catalyst loadings of 10 mole% were employed, but in addition to desired alkenyl tosylate 6 11 double substitution product 6 12 was also observed. After purification, compound 6 11 was recovered in very low yields. Table 6 1. Effect of coppe r species on Grignard coupling. Type of Cu species Mole% Solvent Yield(%) no ad dition -THF no substitution CuI 10.0 THF 0.5 CuI 10.0 THF/toluene (2:1) 1.6 Li 2 CuCl 4 10.0 THF/toluene (2:1) 5.2 Bu 2 CuLi 10.0 THF/toluene (2:1) 1.8 Increasing the yield of the Grignard reaction shown in Figure 6 2 requires the use of a more efficie nt catalyst system Burns et.al. reported a highly effective copper catalyst for the coupling of Grignard reagents with tosylates and mesylates 208 Synthesis includes the preparation of CuBr SMe 2 LiBr and LiSPh in THF solution to form thiophenol and a LiBr ligated copper species to increase the nucleophilicity of the Grignard reagent. The procedure was previously utilized 118 for the preparation of the hexyl branched symmetrical diene monomer s with shorter ethylene run lengths and moderate yields (55 60%) were obtained for the coupling reaction. This synthetic methodology was e mployed for the preparation of monomer 6 1 7 as shown in Figure 6 3. The symmetrical diene 6 13 starting material with a 9 methylene run length was generated according to a previously published two step alkylation/decyanation procedure 156,157 Hydroboration/oxidation and subsequent mesylation ga ve compound 6 15 in a moderate overall yield (41%). Me sylated di functional alcohol was intended to couple with the Grignard reagent 6 16 in the

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119 presence of an equimolar mixture of copper bromide dimethyl sulfate, lithium bromide and lithium thiophenolate in THF. It is important to note that u nlike the alkenyl tosylate route (Figure 6 2), Grignard coupling is performed aft er the branch incorporation to ensure double substitution wit h 2 equivalents of alkenyl magnesium bromide 6 16 Figure 6 3. Synthetic strategy to generate monomer 6 1 7 with 29 methylene run length. Purifica tion of the crude product yielded a mixture of monomer 6 17 and undesired compound 6 18 During the work up step, unreacted Grignard reagent abstracts a proton from water and forms icos 1 ene ( 6 18 ). Monomer 6 17 could not be isolated because of the insufficient polarity difference between compound 6 17 and 6 18 The successful synthesi s of alkenyl bromide with a 36 methylene run lengt h is shown in Figure 6 4 The scheme includes self metathesis of 20 b romo eicos 1 ene 6 19 ( preparation of compound 6 19 is described in Chapter 4 ) in the prese nce of first generation Grubbs` metathesis catalyst and hydrogenation of unsaturated dibromide 6 20 with Wilki nson`s catalyst to give 1,38 dibromooctatriacontane ( 6 21 ) Because of the

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120 low solubility of compound 6 21 in THF, the reaction temperature was set to 40 o C and 1.5 equivalents of t BuOK was used for dehydrohalogenation of alkyl dibromide 6 21 to suppress (but not eliminate entirely) the formation of the di elimination product 6 23 Figure 6 4. Synthesis of alkenyl bromide 6 22 with 36 methylene run length. T he crude mixture contained the desired alkenyl bromide 6 22 the di elimination product 6 23 and unreacted starting mate rial, all with close retardation factors by thin layer chromatography. Due to the similar polarities of these three species and the relatively low room temperature solubility of the crude mixture in hexane, the special purification procedure was followed. The crude mixture was first dissolved in toluene and mixed with a small amount of silica gel to form a slurry. Toluene was slowly evaporated and the crude mixture adsorbed on silica particles were ad ded on freshly packed ( technical grade hexane is used for column packing) column to form a uniform layer. Then, another uniform layer of pristine silica gel was added on t op of the crude layer. Hexane was slowly added to the column without disturbing both layers. Flow rate of the column was also adjusted to obtain the most efficient separation. U ltrapure silica

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121 gel with small particle size (5 20 m, 60 pore size ) is used for column packing. After four column chromatography passes, the desired alkenyl brom ide 6 22 was recovered in moderate yield (31 %). As described in Chapter 4, alkylation of various primary nitriles with 20 bromoicos 1 ene 6 19 works efficiently and gives the corresponding monomers with different branches in moderate to high overall yields The efficiency of alkylation with a longer alkenyl bromide (in this case 38 bromooctatriacont 1 ene 6 22 ) was reacted with hexanenitrile 6 24 (Figure 6 5) in the presence of lithium diisopropyl amide (LDA) Figure 6 5 Synthesis of symmetrical diene monomer with a butyl branch on every 39 th carbon. Because of the low solubility of 6 22 in THF at low temperatures, toluene was used as a co solvent. However, the low solubility of LDA i n toluene dramatically decreased the efficiency of the alky lation. Thus, the traditional procedu re (ie, addition of base at 78 o C and alkylation at 0 o C) for nitrile alkylation was not followed, and 50 o C was selected as the reaction temperature in THF The elevated temperature increased the likelihood of undesired side reactions, s uch as alkenyl bromide elimination. After purification 2 butyl 2 (octatriacont 37 en 1 yl)tetracont 39 enenitrile ( 6 2 5 ) was recovered in moderate yield (24%). T he decyanation step was also perfor med at

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122 elevated temperature (40 o C) and 39 b utylheptaheptaconta 1,76 diene ( 6 2 6 ) was recovered in a reasonably high yield (88%) 6.2 Polymer Synthesis and Characterization Because of the relatively high melting point of monomer 6 22 (T m =77 o C), the polymerization temperature was set to 100 o C where Ru based catalysts are prone to have low turnover numbers and to generate Ru H species 159 161 which would cause isomerization problems and disrupt the symmetrical nature of the monomer 162,163 Therefore, monomer 6 26 was condensed to form the unsaturated ADMET polymer using Schrocks` [Mo] catalyst for clean metathesis chemistry as shown in Figure 6 6 Figure 6 6 Synthesis of precision polym ers possessing a branch on every 39th carbon. Due to the oxophilic n ature of [Mo] catalysts, all manipulations prior to polymerization and catalyst addition (catalyst to monomer ratio 1:500) were performed in a glove box. Polymerization was initia ted by me lting the monomer at 77 o C and t he temperature was set to 100 o C to be able to stir the viscous polymer melt. After 24 hours of reaction the polymer was cooled to RT another portion of [Mo] catalyst ( catalyst to monomer ratio 1:500 ) was added in a glove b ox and the temperatu re was returned to 100 o C ADMET polymerization proceeded smoothly to give the desired unsaturated linear polymer 6 2 7 with no detectable side reactions. Disappearance of terminal olefin

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123 signals in the 1 H NMR spectrum (Figure 6 7 ) prove d the complete conversion, which is n ecessary for any step growth polymerization. Unsaturated polymer 6 2 7 was hydrogenated utilizing Wilkinson`s catalyst (catalyst to monomer ratio 1:250) to y ield the precision polyethylene (polymer 6 2 8 ) having a butyl b ranch on every 75 th carbon. Figure 6 7. 1 H NMR spectra of monomer ( 6 2 6 ), unsaturated ( 6 2 7 ) and saturated ( 6 2 8 ) polymers. The p olymeriza tion and hydrogenation steps were followed by 1 H NMR spectroscopy. Figure 6 7 shows the 1 H N MR spectra of butyl bra nched polymer, 6 2 8 and its precursors. ADMET p olymerization of monomer 6 2 6 yielded the unsaturated polymer 6 2 7 Formation of the ADMET polymer was evidenced by loss of the terminal olefin signals (5.0 and 5.8 ppm) and the appearance of the internal ol efin resonance at 5.4 ppm ( Figure 6 7 ). Exhaustive hydrogenation of the internal olefins with Wilkinson`s catalyst generated 6 2 8 corresponding to polyethylene with butyl branches on every 75 th carbon with complet e loss of the olefinic signals i n the 1 H NMR spectrum

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124 After the hydrogenation, the solution of saturated polymer was concentrated and precipitated over methanol. It is important to note that the solubility characteristics of polymer 6 2 8 (soluble in toluene, dichlorobenzene, trichlorobenzene, et c. at high temperatures ) are similar to those of polyethylenes prepared by chain polymerization. Table 6 2. Molecular weight data for polymers 6 23 and 6 24 Polymer ( k g/mol) a ( k g/mol) a PDI 6 27 16.3 46.7 2.86 6 28 17.7 50.2 2.83 a Molecular weight data were collected by GPC in 1,2,4 trichlorobenzene at 135 o C relative to polystyrene standards. b PDI, polydispersity index / Molecular weight data w ere obtained using high temperature gel permeation chromatography (GPC) i n 1,2,4 trichlorobenzene at 135 o C relative to polystyrene standards. Table 6 2 presents the molecular weight data for precisely butyl branched unsaturated 6 27 and saturated 6 2 8 poly mer s. Figure 6 8. DSC exotherms (down) and endotherms (up) for unsaturated ( 6 27 ) and saturated ( 6 28 ) polymers. Figure 6 8 shows the DSC thermograms of the unsaturated 6 2 7 and saturated 6 2 8 polymers in both the heating and cooling cycles. The polyme rs are semicrystalline,

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125 having the melting tra nsitions at 95.5 and 104 o C, and as expected, saturation increases both the melting points and the heat of fusion values. The melting transitions of both polymers are sharper than those for chain polymerized pol y(ethylene co hexene) and olefin copolymers, illustrating the importance of precision placement of the branches 209,210 Thermal data for polymer 6 28 and other previously reported precision polyethyl enes with more frequent butyl branches 6 (Table 6 3 ) clearly demonstrate the effect of precision run length in these materials As the run length increases between two consecutive branch points, the melting point g radually increases, approaching that of ADM ET PE (linear PE without branches, T m =134 o C). Table 6 3. DSC data for precision polyethylenes possessing butyl branch. Butyl branch on every n th carbon, n Butyl branches per 1000 carbon atoms T m ( o C) m (J /g) ADMET PE 0 134 204 75 13 104 152 39 26 75 .0 66 .0 21 48 14 .0 47 .0 15 67 33 .0 13 .0 5 200 amorphous --To compare the experimental data for butyl branched precision polymers with theoretical predictions for infinitely long polyethylene int erpreted by Flory 211 a plot of melting point vs number of butyl branches per 1000 carbon s as shown in Figure 6 9. The plot shows good linearity, an indication of the similarity in thermal behavior between ADMET PE and infinitely long PE. Morphological examination by WAXD is illustrated in Figure 6 10 for polymer 6 28 ADMET PE and commercial HDPE made with Mulheim catalyst. The similarity of polymer 6 28 to ADM ET PE and HDPE is obvious: All three polymers exhibit the typical orthorhombic unit cell structure with two characteristic crystalline peaks observed at

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126 21. 5 and 24.0 corresponding to reflection planes (110) and (200), respectively. Unlike the precision polymer 4 29e (butyl) (Figure 5 9 in Chapter 5) the X ray diffractogram of polymer 6 2 8 does not display the crystalline peak at the amorphous halo region, confirming the absence of the metastable phase formation. Figure 6 9. Plot of melting temperatur e vs butyl branch frequency in precision polyethylenes. Increasing the distance between the two consecutive branches from 38 carbons (5.26 mole% branch concentration) to 74 carbons (2.70 mole% branch concentration) fully expels the butyl branches from the crystal lattice to the amorphous phase. Precision polymer 6 2 8 represents the first realistic model of commercial LLDPE reported so far in precision polyolefin research.

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127 Figure 6 10. WAXD diffractograms of precision polymer 6 2 8 ADMET PE, and commercial ly available High Density Polyethylene (HDPE) prep ared with Mulheim catalyst. Data were collected at RT for all polymer samples. 6 .3 Experimental Section 6 .3.1 I nstrumentation All 1 H NMR ( 3 00 MHz) and 13 C NMR ( 75 MHz) spectra were recorded in CDCl 3 unless otherwise stated. Chemical sh ifts were referenced to signals from CDCl 3 (7.24 ppm for 1 H, 77.23 ppm for 13 C) with 0.03% v/v TMS and from C 6 D 6 (7.16 ppm for 1 H, 128.62 ppm for 13 C) as an internal reference. For all the NMR work the solvents were chloroform d or benzene d and the temperature was 25 or 7 5 o C. High resolution mass spectrometry (HRMS) was carried out using a Agilent 6210 TOF MS mass spectrometer in the direct analysis i n real time (DART) mode with an IonSense DART Source. Thin layer chromatograp hy (TLC) was used to monitor all reactions and was performed on glass plates coated with silica gel (250 m thickness). C olumn chromatography was

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128 performed using ultrapure silica gel (40 63 m, 60 pore size). For the purification of 38 bromooctatriacont 1 ene (8), ultrapure silica gel (5 20 m, 60 pore size) was purchased from SiliCycle. Gel permeation chromatography (GPC) was performed using an Alliance GPC 2000 with an internal differential refractive index detector ( DRI), internal differential visco sity detector (DP), and a p recision angle light scattering detector (LS). The light scattering signal was collected at a 15 angle, and the three in line detectors were operated in series in the order LS DRI DP. The chromatography was performed at 135 C us ing a PLgel MIXED B column (10 m PD, 8.0 mm ID, 300 mm total length) with HPLC grade 1,2,4 trichlorobenzene as the mobile phase at a flow rate of 1.0 mL/min. Injections were made at 0.05 0.07% w/v sample concentration using a 322.5 L injection volume. In the case of universal calibration, retention times were calibrated versus narrow range molecular weight polystyrene standards (purchased from Polymer Standard Service PSS in Mainz, Germany). Differential scanning calorimetry (DSC) was performed using a T A Instruments DSC Q1000 equipped with a controlled cooling accessory at a heating rate of 10 C/min unless otherwise specified. Calibrations were made using indium and freshly distilled n octane as the standards for peak temperature transitions and indium for the enthalpy standard. Wide angle X ray (WAXS) powder diffraction data were collected on a Mar345 Image Plate Detector with plate diameter of 345 mm and outside dimens ions (515 mm 398 mm 350 mm). T produced by a g values ranging 1 0 to 40.

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129 6 .3.2 Materials Chemicals were purchased from the Aldrich Chemical Co. and used as received unless otherwise noted. Grubbs ` first generation cataly st, bis(tricyclohexylphosphine)benzylidineruthenium( IV) dichloride, was kindly provided by Materia, Inc. Schrock`s molybdenum metathesis catalyst, [(CF 3 ) 2 CH 3 CO] 2 (N 2,6 C 6 H 3 i Pr 2 )Mo=CHC(CH 3 ) 2 Ph, and W rhodium hydrogenation catalyst RhCl(PPh 3 ) 3 were purchased from Strem Chemical Ruthenium and m olybdenum catalysts were stored in an argon filled glovebox prior to use. Tetrahydrofuran (THF) and toluene were freshly used from Butler Polymer Research Laboratories anhydrous solvent preparation unit. H PLC grade 1,2,4 trichlorobenzene was pur chased from the Applichem GmbH. HDPE is kindly provided by BASF (M n =34000 g/mol and PDI=7.43). All the nitrile s and alkenyl bromide starting materials, as well as hexamethylphosphoramide and diisopropyl amine were di stilled over CaH 2 All reactions were carried out in flame dried glassware under argon unless otherwise stated. 6 .3.3 Proc edures Synthesis of 1,38 dibromooctatriacont 18 ene (6 20 ) Compound 6 19 20 b romo eicos 1 ene ( 4.252 g, 1.18 m mol) was placed in a f lame dried reaction tube under vacuum (10 3 atm) for 2 hours at 75 o C. Grubbs 1 st generation catalyst (0.004 g 4.85 10 3 ) was added, and the mixture was left at 75 o C under vacuum (10 3 atm) for 24 hours. The reaction was quench ed with 5 mL ethyl vinyl ether and dissolved in 15 mL t o luene. The toluene solution was concentrated and the product was precipitated by pouring into 1.0 L of methanol. Crystals were filtered and dried under vacuum overnight. 3.818 g of compound 6 20 was reco vered as white crystals. (Yi eld =94 %) 1 H NMR (CDCl 3 (ppm), 1.20 1.38 (br, 64H, CH 2 ), 2.01 2.08 (q, 4H, allyl CH 2 ), 3.42 (t, 4H, CH 2 Br), 5.39

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130 (m, 2H, vinyl CH) ; 13 C NMR (CDCl 3 130.125 (vinyl CH, cis ), 130.58 (vinyl CH trans ).; DART/HRMS: [M] + calculated for C 38 H 74 79 Br 2 : 688.8422, found: 688.4157. Calculated for C 38 H 74 81 Br 2 : 6692.9042, found: 6692.4304. Elemental analysis calculated for C 38 H 74 Br 2 : 66.07 C, 10.80 H; found: 65.35 C, 10.75 H. Synthesis o f 1,38 dibromooctatriacontan e (6 21 ) Compound 6 20 1,38 dibromooctatriacont 18 ene ( 3.818 g, 0.553 mmol) was dissolved in 50 mL degassed toluene, placed in a Parr bomb with 0.55 mg, 0.85 10 3 mmol Wilkinson `s catalyst and left to react at 90 o C under 900 psi of hydrogen for 36 hours The toluene solution was concentrated and the product was precipitated by pouring into 0.5 L of methanol. Crystals were filtered and dried under vacuum overnight. 3.605 g of compound 6 21 was recovered as white crystals. (Yield = 94 %) 1 H NMR (CDCl 3 ppm), 1.30 1.45 (br, 72H, CH 2 ), 3.42 (t, 4H, CH 2 Br); 13 C NMR (CDCl 3 34.0 DART/HRMS: [M] + calculated for C 38 H 76 Br 2 : 690.4314, found: 690.4261. Elemental analysis calculated for C 38 H 76 Br 2 : 66.07 C, 10.79 H; found: 64. 84 C, 10.75 H. Synthesis of 38 bromooctatriacont 1 ene (6 22 ) In a 250 mL round bottomed flask compound 6 21 ( 3.324 g, 0.481 mmol) was dissolved in a 2:1 toluene /THF (150 mL/75 mL) mixture. The mixture was warmed to 40 o C and potassium tert butoxide ( 0.086 g, 0.771 mmol) was added under a rgon flow The rea ction mixture was stirred at 40 o C for 24 hours. Solvents were evaporated and the crude product was purified by column chromatography using hexane as the eluent and SiliCycle silica gel with 5 20 m particl e size. 0.923 g of compound 6 22 was recovered after purification. (Yield= 31 %) 1 H NMR (CDCl 3 1.45 (br, 68H, CH 2 ), 2.01 2.08 (q, 4H, allyl CH 2 ),

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131 3.42 (t, 4H, CH 2 Br), 4.91 5.04 (m, 4H, vinyl CH 2 ), 5.78 5.87 (m, 2H, vinyl CH); 13 C NMR (CDCl 3 [M] + calculated for C 38 H 75 Br: 609.4974, found: 609.4981. Elemental analysis calculated for C 38 H 75 Br: 74.59 C, 12.35 H; found: 74.22 C, 11.94 H. Synthesis of 2 butyl 2 (octatriac ont 37 en 1 yl)tetraco nt 39 enenitrile (6 25 ) Compound 6 22 (1.290g, 0. 210 mmol) was placed in a flame dried 25 mL reaction tube and stirred under vacuum for 2 hour at 85 o C In a separate flame dried 50 mL 2 neck round bottomed flask, diisopropyl amine ( 0.22g, 2.10 mmol) was dissolved in 5 mL of anhydrous THF. A 1.4 mL sample of 1.5 M (freshly distilled) n BuLi (2.1 0 mmol) was added slowly at 78 o C for 5 minutes under a rgon flow. T he LDA solution was warmed to 0 o C and stirred for 30 minutes, then cooled t o 78 o C prior to adding 0.11g hexanenitrile 6 24 (1.13 mmol) over 5 minutes. The reaction mixture was warmed to 0 o C and stirred for 30 minutes. This solution was slowly transferred via cannula to the reaction flask for the alkylation reaction in one portio n at RT (alkylating agent 6 22 was not soluble at RT in THF). The reaction temperature was increased to 50 o C to dissolve compound 6 2 2 and stirred for 12 hours under a rgon flow. The s olvents were evaporated and the crude product was purified by column chro matography using (hexane/toluene 9:1) as eluent. 0.292g, 0.025 mmol, of compound 6 25 was recovered as a white solid. (Yield= 24 %) 1 H NMR (CDCl 3 3 ), 1.22 1.34 (br, 146H, CH 2 ), 2.01 2.08 (q, 4H, allyl CH 2 ), 4.90 5.03 (m, 4H, viny l CH 2 ), 5.76 5.88 (m, 2H, vinyl CH); 13 C NMR (CDCl 3 114.3, 124.8, 139.5; DART/HRMS: [M] + calculated for C 82 H 159 N: 1159.2545, found:

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132 1159.2538. Elemental analysis calculated for C 82 H 159 N: 84.97 C, 13.83 H, 1.21 N; found: 85.06 C, 13.66 H, 1.23 N. Synthesis of 39 but ylheptaheptaconta 1,76 diene (6 26 ) Potassium metal (0.340g 8.69 mmol), HMPA ( 0.9mL 4.87 mmol), and anhydrous THF (45 mL) were transferred to a 100 mL flame drie d 3 necked round bottomed flask equipped with a stir barr. Compound 6 25 (0.292g, 0.025 mmol) was added to the slurry in one portion at RT under a rgon flow. T he temperature was raised to 40 o C to dissolve compound 6 25 and 0.45 mL of t BuOH (7.78 mmol) was added. The reaction mixture was stirred for 24 hours and then quenched with isopropan ol (10 mL) The s olvents were evaporated and the crude product was purified by column chromatography using hexane as the eluent. 0.253g, 0.022 mmol, of compound 6 26 was r e covered as a white solid. (Yield= 88 %) 1 H NMR (CDCl 3 3 ), 1.24 1.32 (br, 146H, CH 2 ), 1.35 1.41 (m, 1H, CH), 2.01 2.08 (q, 4H, allyl CH 2 ), 4.90 5.03 (m, 4H, vinyl CH 2 ), 5.76 5.88 (m, 2H, vinyl CH); 13 C NMR (CDCl 3 32.1, 33.9, 34.0, 34.2, 37.8, 114.3, 139.5; Elemental analysis calculated for C 81 H 160 : 85.78 C, 14.22 H; found: 85.52 C, 14.36 H. Polymerization of 39 but ylheptaheptaconta 1,76 diene (6 27 ) Compound 6 26 ( 0.155 g, 0. 137 mmol) was placed in a 25 mL reaction tube and le ft under vacuum for 2 hours at 90 o C The reaction tube was cooled to RT and placed into the glove box. Schrock `s c atalyst (0.09g) was added, and the reaction tube was placed under vacuum again. Polymerization was started by raising the temperature to 100 o C and the mixture was left under vacuum for 24 hours. Polymerization was quenched by opening t he tube to the air and dissolving the contents in 10 mL of toluene. After precipitation over 0.5 L

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133 of methanol and filtration, 0.130 g of polymer 6 27 was recover ed as a white solid. (Yield=84%) 1 H NMR (CDCl 3 3 ), 1.21 1.36 (m, CH 2 ), 1.98 (q, allyl CH 2 ), 5.40 (m, vinyl CH); 13 C NMR (CDCl 3 4.26, 23.36, 27.05, 29.46, 29.99 30.43, 32.77, 33.81, 34.22, 37.83, 130.53 Synthesis of polymer (6 28 ) In a 125 mL Parr bomb glass sleeve, unsaturated polymer 6 27 (0. 110 g) was dissolved in 5 0 mL of degassed toluene. Wilkinson`s hydrogenation catalyst (0.7 mg 7.6 10 4 mmol) was added, and the bomb was charged with 900 psi of hydrogen. The reaction was allowed to proceed for three days at 9 0 o C. The polymer solution was concentrated and precipitated in 0.5 L of methanol The precipitate was filtered and dried under vacuum overnight. 0.95 g of polymer 6 28 was recovered as a white solid. (Yield=86%). 1 H NMR (C 6 D 6 3 ), 1.21 1.47 (m, CH 2 ), 1.56 (m, CH); 13 C NMR (C 6 D 6

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134 CHAPTER 7 SUMMARY AND OUTLOOK Metathesis polycondensation chemistry has been employed to control the crystalline morphology of Linear Low Density Polyethyl ene (LLDPE) by precisely introducing alkyl branches along the polymer backbone. These polymers, while structurally akin to copolymers made via chain copolymerization of ethylene and vinyl com onomers, have unique properties because use of symmetrical diene monomers ensures precise spacing of the chain branches An important limitation in this work was synthesis of the symmetrical diene monomers required in this chemistry. Spacing in the symmetrical monomer directly determines the precision run le ngths in the polymer: P rior monomer synthetic schemes have limited the maximum run lengths between branch points along the polymer to 20 methylene carbons (ie, a branch placed on each and every 21 st carbon ). The p resent work desc ribed the systematic increase of precision run lengths to 38 and 74 methylene carbons. Successful preparation of symmetrical dienes for both run lengths was presented. For the case of 38 run lengths, the synthesis and characterization of precisely sequenced polyethylenes containing th irteen different branches allowed systematic examination of the effect of branching on polyethylene properties. A clear change in morphology was observed for these polymers from a situation where the methyl one where branc hes of greater mass are partially expelled from the unit cell to form m etastable crystalline morphologies T he precision LLDPE model polymers were characterized with Differential Scanning Calorimetry (DSC), Infrared Spectroscopy, Sol id Stat e Nuclear

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135 Magnetic Resonan ce Spectroscopy, Wide Angle X ray Scattering (WAXS) and Transmission Electron Microscopy (TEM). Precision polymer with butyl branches on every 75 th carbon was successfully prepared and X ray investigation of this polymer displayed an orthorhombic unit cell structure with the absence of metastable phase formation. Increasing the distance between the two consecutive branches from 38 carbons (5.26 mole% branch concentration) to 74 carbons (2.70 mole% branch concentration) fully expels the butyl branches from the crystal lattice to the amorphous phase. This precision polymer with butyl branches on every 75 th carbon represents the first realistic model of commercial LLDPE reported so far in precision polyolefin research. Characterization of these precisely branched polymers should be continue d to in clude temperature dependent WAXD, SS NMR and TEM analysis of all the precision polymers described in this document. With the present level of advancement in precision polyolefin research, study of the effect of long chain branching in polyethylene is now possible In the future, the m odel polymers should be prepared to mirror the commercial metall ocene systems.

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136 APPENDIX DSC PROFILES OF PREC ISION POLYMERS DSC profiles of precision polymers with a branch on every 39 th carbon. 2 nd heating and 2 nd cooling curves are show n (heating and cooling rate= 10 o C/min).

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155 BIOGRAPHICAL SKETCH Bora Inci was born in Aydin, Turkey in 1982. He is a son of Fikriye Inci and Sezgin Inci. After finishing Bursa Ali Osman Sonmez Science High School, he enrolled in Bilkent University chemistry department. During his last two years of undergraduate studies he worked with Professor Sefik Suzer on X ray photoelectron spectroscopy analysis of rough surfaces. He received his B.S. in 2005 and joined to Koc University, Istanbu l, Turkey for his M.S. degree in the m aterial science and engineering program. He worked under the guidance of Prof essor characterization of segmented polyurethanes. Bora moved to the University of Florida and joine d the Wagener group in the fall of 2007. While at Florida, he was able to expand and develop the ongoing modeling polyethylene project. Part of his graduate studies, he joined the Prof. Katharina Landfester `s Research G roup at Max Planck Institute for Poly mer Research at Mainz, Germany as a visiting scientist for the period of three months. He is recipient of 2009 Proctor & Gamble Research Excellence and 2010 Butler Polymer Research Awards. He likes playing soccer and is the captain of the chemistry soccer at University of Florida