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Chemistry of Latent Reactive Polycarbosilane/Polycarbosiloxane Elastomers via Acyclic Diene Metathesis (ADMET) Polymerization

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Chemistry of Latent Reactive Polycarbosilane/Polycarbosiloxane Elastomers via Acyclic Diene Metathesis (ADMET) Polymerization
Creator:
MATLOKA, PIOTR PAWEL ( Author, Primary )
Copyright Date:
2008

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Subjects / Keywords:
Alkenes ( jstor )
Catalysts ( jstor )
Copolymers ( jstor )
Dienes ( jstor )
Macromolecules ( jstor )
Metathesis ( jstor )
Monomers ( jstor )
Polymerization ( jstor )
Polymers ( jstor )
Silicon ( jstor )

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University of Florida
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University of Florida
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Copyright Piotr Pawel Matloka. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Embargo Date:
4/30/2005
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436097568 ( OCLC )

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CHEMISTRY OF LATENT REACTIVE POLYCARBOSILANE/POLYCARBOSILOXANE ELASTOMERS VIA ACYCLIC DIENE METATHESIS (ADMET) POLYMERIZATION By PIOTR PAWEL MATLOKA A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2004

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ii ACKNOWLEDGMENTS Many people have been instrumental in my career at the University of Florida. First, I would like to tha nk my advisor (Professor Ken Wagener) for all of his good advice and for having confidence in my abilities as a chemist. Next, I would like to thank Mr. John Sworen, for taking the time to teach me good laboratory techniques, for introducing me to my project ear ly in my graduate career, an d for being a true friend. I thank all of the members of the Wagener res earch group for their helpful discussions and friendship. I would like to thank my pa rents for all of their enduring supp ort during my many years of education. They have made many sacr ifices to get me where I am today. They taught me at a young age what was important in life, and showed me how to work hard to achieve my goals. Finally, but definitely not last , I would like to thank my l ovely wife Kornelia for all her love and patience. I apprecia te her support and belief in me.

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iii TABLE OF CONTENTS page ACKNOWLEDGMENTS..................................................................................................ii LIST OF TABLES...............................................................................................................v LIST OF FIGURES...........................................................................................................vi ABSTRACT.....................................................................................................................vi ii CHAPTER 1 INTRODUCTION........................................................................................................1 1.1 Silicon Chemistry...................................................................................................2 1.2 Olefin Metathesis....................................................................................................3 1.3 Olefin Metathesis Containing Silicon.....................................................................6 1.4 Acyclic Diene Oligomerization and Po lymerization of Dienes Containing Silicon......................................................................................................................8 2 SYNTHETIC MODIFICATION OF CROSSLINK DENSITY AND SOFT SEGMENT IN POLYCARBOSILANE/POLYCARBOSILOXANE ELASTOMERS..........................................................................................................17 2.1 Synthetically Modified Crosslink Density............................................................18 2.2 Synthetic Soft Segment Modification...................................................................23 2.3 Conclusions...........................................................................................................27 3 EXPERIMENTAL METHODS.................................................................................29 3.1 General Considerations.........................................................................................29 3.2 Materials...............................................................................................................30 3.3 Monomer Synthesis..............................................................................................30 3.3.1 Synthesis of tris(4-pen tenyl)methylsilane (62).........................................31 3.3.2. Synthesis of di(4-pentenyl)dimethoxysilane (65)....................................31 3.3.3 Synthesis of diundecenyldiethylene glycol (67)........................................32 3.3.4 Synthesis of diundecenyltriethylene glycol (68).......................................33 3.3.5 Synthesis of diundecenyltetraethylene glycol (69)....................................33 3.4 General Metathesis Conditions.............................................................................34 3.4.1 Polymerization of di(4-p entenyl)dimethoxysilane (65)............................34

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iv 3.4.2 Polymerization of diundecen yltriethylene glycol (68)..............................35 3.4.3 Tripolymerization of monomers 57, 58, and 62........................................35 3.4.4 Tripolymerization of monomers 57, 68, and 62........................................36 REFERENCES..................................................................................................................37 BIOGRAPHICAL SKETCH .............................................................................................41

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v LIST OF TABLES Table page 1 Comparison of various silicon a nd carbon bond lengths and energies......................3 2 Synthetic research objectives...................................................................................17 3 Mechanical properties of the unsatur ated ADMET copolymers and commercially available elastomers.................................................................................................26

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vi LIST OF FIGURES Figure page 1 General scheme of olefin metathesis..........................................................................4 2 Well-defined metathesis catalysts..............................................................................5 3 The metalacyclobutane mechanism...........................................................................5 4 The catalytic cycle of ADMET polymerization.........................................................6 5 Ring opening metathesis polymerizati on of 1,1-dimethyl-1-silacyclopent-3-ene.....7 6 Ring opening metathesis of silylsubstituted norbornens............................................8 7 Ring opening metathesis polymerizat ion using CaseyÂ’s carbene complex................8 8 Polymerization of diallyland allyl-butenyl derivatives of disubstituted silanes......9 9 Polymerization of diallyltetramethyldisiloxane.......................................................10 10 Metathesis of diallyltetramethyldisilane..................................................................10 11 Metathesis of dialkenylsilacyclobutane...................................................................11 12 Copolymerization of divinyldimethylsilane with 1,9-decadiene.............................11 13 Productive and non-productive metathesis. A) Metathesis, B) Co-metathesis........12 14 Polycarbosilanes via ADMET..................................................................................13 15 ADMET polymerization of s iloxane containing dienes...........................................14 16 The latent reactivity concept to pr oduce different materials behavior.....................15 18 Chain-end crosslinking molecules...........................................................................19 19 Chain-end crosslinking in th e Polycarbosilanes via ADMET.................................20 20 Synthesis of monomer 65 .........................................................................................21 21 1H NMR spectra of monomer 65 and its polymer 66 ...............................................22

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vii 22 Soft phase monomers based on polyoxyethylene....................................................24 23 1H NMR spectra of monomer 69 ..............................................................................24 24 Glass transition temperatures for various lengths of polyoxyethylene....................25 25 High elastic material cont aining increased soft phase and chain-end crosslinker...27

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viii Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science CHEMISTRY OF LATENT REACTIVE POLYCARBOSILANE/POLYCARBOSILOXANE ELASTOMERS VIA ACYCLIC DIENE METATHESIS (ADMET) POLYMERIZATION By Piotr Pawel Matloka May 2004 Chairman: Kenneth B. Wagener Major Department: Chemistry Acyclic diene metathesis (ADMET) has been used in the synthesis of carbosilane and carbosiloxane polymers bearing a latent reactive methoxy-func tional group on each repeat unit. The polymerization results in a linear thermoplastic polymer. The latent reactive methoxy groups remain inert duri ng polymerization; however, exposure to moisture triggers hydrolysis and the formati on of a chemically crosslinked thermoset. The thermosetÂ’s properties can be modified by varying the ratio of carbosilane and carbosiloxane repeat units in the final material. Synthetic modification of crosslink density and run length of the soft phase in polycarbosilane/polycarbosiloxane elastomers is also discussed. We introduced a trifunctional ADMET active chain-end crosslinke r to our previous system in order to improve mechanical behavior. The resultant film (64) exhibits an enhancement in elastic properties. Changing a soft phase from th e siloxane unit to the polyoxyethylene glycol

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ix further enhances material pr operties. Crosslinked film (67) containing chain-end, chain-internal crossli nks and the diundecenyl triethylene glycol in a soft phase exhibit good material properties (modul us 6 MPa, elongation 500%).

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1 CHAPTER 1 INTRODUCTION Organosilicon chemistry (as an inherent part of organometallic chemistry) is one of the most rapidly developing fields of sc ience. Throughout nature, there are many well-known inorganic and polymeric compounds containing silicon. However, since KippingÂ’s pioneer work at the beginning of the 20th century, researchers have oriented their focus on compounds containing siliconcarbon hybrids, rather than on purely inorganic structures. Over the decades si licon/carbon-based copolymers have garnered the interest of researchers because of their enhanced material properties, which cannot be attained by organic poly mers based on carbon alone.1 The copolymersÂ’ uniqueness has centered on their high thermal stability, good el ectrical resistance, low surface tension, release and lubrication prope rties, high hydrophobicity, low glass transition, and low toxicity for the natural environment.2 Although such hybrid copol ymers are difficult to prepare, research conducted by McGrath,3 Webber,4 and Interrante5 has been instrumental in defining viable synthetic routes toward these materials. The simplest and most widely known organosilicon polymers are based on silicones or polysiloxanes. This genera l class, well known for over 100 years, posses many valuable and unique properties. Silicones in particular, like polydimethylsiloxanes (PDMS), exhibit hydrophobicity, thermal and oxidative stability, el ectrical resistance, low glass-transition temperature, low envi ronmental toxicity, gas permeability, and antiadhesive properties. However, silicone elastomers based on polydimethylsiloxane

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2 (PDMS) alone exhibit relatively weak mechanical properties.1 To improve their mechanical performance (thereby extending their commercial use), researchers have modified these silicon-based materials. Th e most economically viable method has been the incorporation of silica-based fillers within the polymerÂ’s matrix. For example, fillers have been shown to impart elongation and ove rall mechanical properties of the material.6 Enhancements of these silic on-based materials (PDMS) can also be realized by the incorporation of carbon segments resulting in silicon/carbon copolymers, which can be achieved via block or grafted copolymers. There are numerous examples of these hybrid materials based on PDMSblock -polysulfone,7a PDMSblock -poly(methyl methacrylate),7b PDMSblock -polyamide-6,7c PDMSblock -poly( -methylstyrene),7d PDMSblock -(bisphenol A polycarbonate),7e PDMSblock -polystyrene,7f poly(vinyl alcohol)graft -PDMS,7g and segmented polyurethanegraft -PDMS.7h Silicon-based hybrids are not the only example of organosilicon copolymers. Progress in organometallic chemistry and in th e chemistry of novel materials have led to the production of new silicon-containing materials such as polycarbosilanes and polycarbosiloxanes. These saturated or uns aturated materials offer many potential industry applications, and produce new challeng es for organosilicon chemists. Recently, these materials have found utility in gas separa tion membranes or as ceramics precursors. 1.1 Silicon Chemistry Silicon being a second row element, residi ng directly under carbon in the periodic table, suggests similar chemistry and reactivit y to that of carbon. Silanes when compared to their analogous carbon compounds, particul arly in nucleophilic substitution, exhibit enhanced reactivity and relative rates. This trend can be related to siliconÂ’s larger size and lower electronegativity, and the atomÂ’s availability to impart low-energy orbital

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3 bonding. Table 1 shows the bond lengths and bond energies of various carbon and silicon bonds with other elements.8 Table 1. Comparison of various silic on and carbon bond lengths and energies. Bond Bond Length (Ã…) Bond Energy (kJ/mol) Si-C 1.90 318 C-C 1.54 334 Si-O 1.63 531 C-O 1.44 340 Si-Cl 2.11 471 C-Cl 1.81 335 Correlations to siliconÂ’s reactivity or st ability can be made and explained using Table 1. For example, silicon-halogen bonds are easily cleaved by nucleophiles while resistant to homolytic fission. Thes e observation are realized by the large electronegativity differences and high polar izability of both atoms producing highly ionic bond in character.9 Also, silicon-oxygen bonds (siloxane s and silanols) are not analogous to carbon-oxygen sigma bonds (ethers and al cohols). The lone pairs on oxygen can overlap with an empty d-orbital on silic on, resulting in a highly polarized bond. Recently, it was shown that * orbitals can participate in back-bonding because of their lower energy versus empty d-orbitals.10 This interaction justifies the fact that silanols are stronger proton donors than aliphatic alcohols a nd that the decrease in the basicity of oxygen is observed in the following orde r: C-O-C > Si-O-C > Si-O-Si. 1.2 Olefin Metathesis Olefin metathesis is described as an in tramolecular and intermolecular exchange of substituents on 1, 2 di-, tri-, or tetraf unctional double bonds. Its name (proposed by

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4 Calderon, Chen, and Scott in 1967) originates from the Greek word metathesis (meaning changing or exchanging positions). However, Banks and Bailey from Philips Petroleum conducted the first research on olefin metath esis and its industria l application in 1964. They observed what they called olefin dispr oportionation in the presence of a heterogenic catalyst.11 A general scheme for olefin metathesis is shown in Figure 1. R1R2R3R4R2R4R1R3+ + Figure 1. General scheme of olefin metathesis Olefin metathesis is a catalytically initiated reaction in which numerous catalyst systems tend to be active. These catalyst sy stems, either homogeneous or heterogeneous, contain transition metals such as molybdenum , tungsten, rhenium, tantalum, ruthenium, rhodium, or titanium.12 Common to industrial applica tions, the catalyst systems are typically heterogeneous versi ons of either Mo, W, or Rh oxides or carbonyls supported on highly developed Al2O3 or SiO2. Very often in these systems, the presence of a cocatalyst is required, usually a Le wis acid based on a main group tr ior tetravalent metal. On the other hand, coordination complexes, or homogeneous systems, can be active with or without the presence of this co-catalyst. These catalyst systems can be split into three categories based on the commonly used carbene complexes and their formation – systems containing long-lived (well-defined) meta l carbenes; metal complexes requiring a carbene generating co-catalyst; or heterogeneous systems. A special class of long-lived (well-defined) carbene complexes devel oped during the 1990s is shown in Figure 2.

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5 N WO O CHR' CF3CF3F3C F3C CH3H3C R'= t -Bu; N MoO O CHR'' CF3CF3F3C F3C CH3H3C Ru PCy3Ph PCy3Cl Cl Ru Ph PCy3Cl Cl N N R''= -C(Me)2Ph (1) (2) (3) (4) Figure 2. Well-defined metathesis catalysts Several mechanisms were initially proposed to account for all observed exchange products. The process most consistent involves subsequential bond breaking and reformation following a transition metal 2+2 cycloaddition/retroaddition mechanism. The Chauvin mechanism13 (Figure 3), is still the most wide ly accepted with both metalaand carbene intermediates.14 [M]C R H [M]C R' H [M]C R' H [M]C R H R'HCCHR RHCCHR R'HCCHR R'HCCHR' + + [M] C C C HR H R R'H [M] C C C HR' R' H HR + + Figure 3. The metalacyclobutane mechanism An extension of metathesis used to pr oduce well-defined unsaturated polymers was first investigated by Wagener.15 Acyclic diene metathesis requires a , diene in conjunction with constructive cleavage to produce high molecular polymer. The

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6 mechanism of the ADMET polymerizati on cycle (Figure 4) has been well documented,15,16 where coordination of the olef in, followed by formation of a metalacyclobutane intermediate, and productive cleavage leads to the formation of the metathesis active alkylidene complex (7) . These subsequent reactions produce the methylidene complex (9) , and the continuation of the cycle proceeds by the coordination of another monomer, productive cleava ge, and the releas e of ethylene. R LnM R' LnM R LnMR R LnMCH2LnM R R H2CCH2+ R R R LnM R R' LnM R' R R' 5 6 7 8 9 10 Figure 4. The catalytic cy cle of ADMET polymerization These discoveries and developments in the field of olefin metathesis and organometallic chemistry led researches to pur sue the usage of metathesis as a convenient tool in the synthesis of functionalized olef ins. The interest in silicon-carbon based hybrids has observed attempts to use olefin me tathesis in the synthesis of such hybrids. 1.3 Olefin Metathesis Containing Silicon In the early seventies, research on meta thesis was focused on producing materials from simple silicon functionalized olefins. Friedman in 1971 produced the first example of these materials by the me tathesis of monoalkenylsila nes in the presence of

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7 alumina-molybdenum.17 Beyond these simple material s, a variety of organosilicon compounds can be produced using metathesis exhibiting good optoele tronic, electronic, and thermal properties. Extensions beyond th is earlier organosilicon chemistry can be divided into three categories: Ring opening metathesis polymerizati on of unsaturated silacycloalkenes Ring opening metathesis polymerization of silylsubstituted cycloalkenes Acyclic diene metathesis polymerization containing silicon First, the ring opening metathesis polymerization of the unsaturated silacycloalkenes leads to polymers containing silicon atoms incorporated in the carbon backbone, as the one shown in the Figure 5. The metathesis of 1,1-dimethyl-1silacyclopent-3-ene (11) can proceed in the presence of tungsten18 or alumina-rhenium19 and offers a broad scope for all silacycl oalkenes, except for the thermally stable silacyclohexene derivatives. Si CH3H3C Si cat.n n (11) (12)CH3CH3 Figure 5. Ring opening metathesis polymeriza tion of 1,1-dimethyl-1 -silacyclopent-3-ene Second, ring opening metathesis polymerizati on of silylsubstituted olefins leads to unsaturated polymers (Figure 6) containing pendant silyl gr oups used to modify the polymerÂ’s properties. One such example is the ring opening metathesis polymerization of silylsubstituted norbornens (13) in the presence of eith er the homogeneous tungsten catalyst or the heterogeneous alumina-rhenium catalyst.20

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8 R Rn ncat.R = SiMe3, SiMe2CH2SiMe3, SiCl3, Si(OEt)3(13) (14) Figure 6. Ring opening metathesis of silylsubstituted norbornens Another interesting exampl e of ring opening metathesis polymerization is the reaction of 1-(trimet hylsilyl)cyclobut-1-ene (15) in the presence of CaseyÂ’s carbene complex (Figure 7).21 The resultant polymer (16) showed a repeating head-to-tail structure containing only the cis double bond configuration. SiMe3cat.n ncat. = (CO)5W=CPh2(15) (16)SiMe3 Figure 7. Ring opening metathesis polyme rization using CaseyÂ’s carbene complex 1.4 Acyclic Diene Oligomerization and Polym erization of Dienes Containing Silicon Acyclic diene metathesis of silicon containing compounds is the most universal method used for the synthesis of organosilic on oligomers or polymers. Metathesis of dialkylsiloxane, dialkenylsiloxa ne and disilane derivatives can be achieved either by an intramolecular or an intermol ecular approach. In all case s, the intermolecular reaction, ADMET, produces linear, unsaturated polycarbo silane or polycarbosiloxane oligomers or polymers. Unsaturated heterocyclic or ganosilicons can also be produced by the intramolecular reaction if pref erred. The mechanism undertaken is strictly dependent on the structure of the initial , -diene, and the respective substituents on silicon.

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9 Additionally, the stability and possible formation of hetero cyclic rings influence the reaction. Of course, six membered ring fo rmation being the most thermodynamically stable. Since all possible pathways are in equilibrium both the seven and five membered rings are rarely observed. In some cases, product formation can be influenced, to some extent, by the presence or absence of solvent in the reaction environment. The first information regarding metathesis and co-metathesis reactions were published in early eighties. The reactions reported by Vdovin et al . utilized the heterogeneous Re2O7/Al2O3 catalyst along with a tetraalky ltin or tetraa lkyllead cocatalysts. VdovinÂ’s and FinkelshteinÂ’s resear ch interest was focused on polymerization of diallyl and the allyl-butenyl derivatives of methyl, ethyl, and phenyl substituted silanes,2225 as presented in Figure 8. Si R1R2Si Si R1R2R1R2n n n x Si Si R1R2R1R2n n x Si R1R2n [Re] -C2H4, 35o C + +[Re] = Re2O7/Al2O3 + Sn(or Pb)R4R1 = R2 = Me, Et or R1 = Me, R2 = Ph where: n = 1; R1 = R2 = Me where n = 2; x = 1-4(17) (18) (19) (20) Figure 8. Polymerization of diallyland allyl-butenyl derivatives of disubstituted silanes The polymerization of dial lyltetramethyldisiloxane (21) , Figure 9, and diallyltetramethyldisilane (25) (Figure 10), were performed in the presence of Re2O7/Al2O3+Sn(Pb)R4.26,27 In the case of dial lyltetramethyldisiloxane (21) , the process

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10 was accompanied by partial cleavage of the Si-Callyl and Si-O bonds resulting in dissproportionation of the Si-O bonds and formation of polysiloxane chains. Si O Si Si O Si Me Me Me Me Me Me Me Me Si O Si Me Me Me Me m n Si O Si Me Me Me Me cat. + + 40 % 25 % 1214 % C2H4(21) (22) (23) (24) Figure 9. Polymerization of diallyltetramethyldisiloxane In the case of diallyltetramethyldisilane (25) , the polymerization leads to formation of both linear and cyclic produc ts, where the former predominates (Figure 10). The favor of the cyclized product (27) can be attributed to the highe r stability of the six membered disilane product. Si Me Me Si Me Me cat. C2H4Si Si Me Me Me Me n Si Si Me Me Me Me + 15 % 80 % (25) (26) (27) Figure 10. Metathesis of di allyltetramethyldisilane Many attempts have focused on the additi on of secondary reac tivity to siliconbased polymers. An interesting example uses ADMET polymerization of dialkenysilanes containing the highly reactive silacyclobutane (Figure 11). Finkelshtein observed that

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11 metathesis occurs in the same manner as fo r any other dialkenylsilanes while maintaining the highly reactiv e silacyclobutane.26,28 SiSi n m Si n + cat. C2H4n = 1, 2 n (28) (29) (30) m =1-3 Figure 11. Metathesis of dialkenylsilacyclobutane High conversions and high pr oducts yields have been observed in all the above mentioned cases. In all reactions, the formati on of either linear or cyclic products proves that metathesis, using the alumina-rhenium catalyst system, is a convenient method for the synthesis of silicon containing oligomers. In the early 90Â’s Wagener and co-workers29-32 opened a new chapter in the synthesis of unsaturated polycarbosilanes and polycarbosiloxanes with acyclic diene metathesis polymerization using well-defined ADMET catalysts (Figure 2). The first silane diene, dimethyldivinylsilane (31) ,29 subjected to ADMET polymerization turned out not to polymerize in the presence of the tungsten based SchrockÂ’s catalyst (1) . Si CH3CH3[W] -C2H4n 6 + 6 (31) (32) (33) Si CH3CH3m Figure 12. Copolymerization of divinyl dimethylsilane with 1,9-decadiene The lack of productive metathesis was a ttributed to steric influences of the trisubstituted silicon atom adjacent to th e double bond. Similar results were obtained by

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12 Schrock and coworkers with the attempte d metathesis of vinyltrimethylsilane.33 However, divinyldimethylsilane (31) does copolymerize with 1,9-decadiene (32) , Figure 12. Finkelshtein provides a differe nt explanation of divinyldi methylsubstituted silanes unreactivity in acyclic diene metathesis pol ymerization, based on the formation of the highly stable silylated carbene complex (37) , Figure 13.25 LnWSi CH3CH3Si H3C H3C LnW=HCSi CH3CH3Si CH3CH3Si Si CH3CH3CH3CH3LnW=CH2+ + (34) (35) (36) (37) (38) LnWSi CH3CH3R LnW Si CH3CH3Si R CH3CH3LnW=CH2+ + R (39) (40) (41) (35) (38) Figure 13. Productive and non-productive metath esis. A) Metathesis, B) Co-metathesis During the homopolymerization of divinyl silanes formation of the metathesis active methylidene complex (35) competes with the inactive silylated carbene (37) . The reaction goes through the thermodynamically more favorable process with the formation A B

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13 of the stablized silylated carbene (37) and thus the metathesis pr oduct is not observed. In the case of copolymerization, the stability of either carbene complex does not differ significantly and two pathways are possible. The productive copolymer formation is realized along with the unproductive form ation of the starting divinylsilanes. Further investigations have shown th at monomers with methylene spacers incorporated between the silicon atom and the olefin can undergo productive metathesis polymerization (Figure 14).29 Successful ADMET polymerization produces unsaturated polymers containing predominately trans double bonds. Exceptions are observed when polymerizing stiffer carbon segments; for example, the polymerization of 1,4-bis(dimethylallylsilyl)benzene (46) results in a 47% cis configuration along the unsaturated backbone. Si CH3CH3Si CH3CH3Si Si CH3CH3CH3CH3Si Si CH3CH3CH3CH3[W] n [W] -C2H4-C2H4Si Si CH3CH3CH3CH3Si Si CH3CH3CH3CH3n n [W] -C2H4(42) (43) (44)(45) (46) (47) Figure 14. Polycarbosilanes via ADMET.

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14 A similar investigation of ADMET has shown that siloxa nes are also polymerizable with SchrockÂ’s molybdenum catalyst (Figure 15 ). Polymerization leads to formation of unsaturated polycarbosiloxanes.30,31 Si O Si CH3CH3CH3CH3Si O Si CH3CH3CH3CH3Si O Si CH3CH3H3C H3C Si O Si O Si CH3CH3CH3CH3CH3CH3[Mo] no metathesis [Mo] -C2H4[Mo] -C2H4Si O Si O Si CH3CH3CH3CH3CH3CH3n Si O Si O Si CH3CH3CH3CH3CH3CH3Si O Si O Si CH3CH3CH3CH3CH3CH3n [Mo] -C2H4(48) (49) (50) (51) (52) (53) (54) Si CH3CH3O Si CH3CH3Si CH3CH3O Si CH3CH3Si CH3CH3O Si CH3CH3Si CH3CH3O Si CH3CH3n [Mo] -C2H4(55) (56) Figure 15. ADMET polymerization of siloxane containing dienes

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15 Similar to divinyldimethylsilane, sterics ha s a predominant effect on both the productive and non-productive metathesis rates of vinylcarbosiloxane (48) . Whereas, the polymerization of 1,3-diallyl1,1,3,3-tetramethyldisiloxane (49) leads to ring formation.34 Siloxanes increased flexibility requires longer distances between the olefin and silicon to produce ADMET linear polymers as shown in the Figure 15. The clean and efficient chemistry afforded by ADMET allows for the combination of the best material properties of both carbon and silicon into a precise random linear copolymer. Moreover, the high se lectivity of olefin metathesis allows for a wider range of possible functional handles to manipulat e the overall material properties. The behavior of ADMET polycarbosil ane/polycarbosiloxane copolymers can be achieved by selecting the appropriate molar concentrati ons of each monomer. Figure 16 illustrates this modular approach and shows that it can be used to generate a large number of materials. Hard Soft Hard Soft Hard SoftOCH3OCH3Latent Reactive Carbosilane Hard Soft + ElastomerIntermediate Properties Plastic Low (10%) Hard Segment Content High (> 90%) Hard Segment Content Equal Ratios (50/50) Figure 16. The latent reactiv ity concept to produce diffe rent materials behavior Expanding beyond this concept to include in ternal crosslink s ites has produced highly solvent resistant and t unable carbosilane/carbosiloxane thermoplastic elastomers.

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16 This research will focus on the recent synthetic advancements of more flexible soft segments, soft phase extensions, and crossli nking modifications in attempt to produce solvent resistant, durable thermosets.

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17 CHAPTER 2 SYNTHETIC MODIFICATION OF CROSSL INK DENSITY AND SOFT SEGMENT IN POLYCARBOSILANE/POLY CARBOSILOXANE ELASTOMERS Since the goal of the research is to produ ce solvent resistant and durable thermosets based on polycarbosilanes, we focused on the factors influencing tensile strength and other mechanical properties in order to impr ove our initial material (Figure 17). Our initial silicon thermoset copolymers produced freestanding films exhibiting low tensile strength and poor material properties. Of course, the latent reactive methoxy bonds are not metathesis labile and do not interfere with the polym erization mechanism. Our understanding has led us to synthesize a nd modify our carbosilane/carbosiloxane monomers to produce better materials. For in stance, we looked into the two controlling factors in an attempt to enhance our mech anical properties, monomer identity and crosslinking density (Table 2). Table 2. Synthetic research objectives Research Objectives Schematic Representation Benefit Synthetically modified crosslink density H3COSi H3CO H3COxChain-end latent crosslinking Will enhance tensile strength and mechanical durability. Synthetic soft segment modification SiOSi CH3CH3CH3CH3x yIncreased run length in soft segment (y>1) Will significantly improve degree of elasticity, degree of elastic recovery, and the propensity for phase separation. Moreover, the run length of soft phase se gments between cross link sites must be controlled and may be a more predominant factor when trying to enable elastic behavior.

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18 The copolymers produced using our ADM ET methodology follow the same trends and criteria as previously discussed silic ones. In our case, th e carbosiloxane monomer contains a single siloxane bond (Si-O-Si) gi ving flexibility and mobility, while the carbosilane monomer lacks any flexibility and mobility once crosslinked. As mentioned, we can produce a wide range of copolymers e xhibiting high elasticity (high percentage of siloxane) or rigid plastics (l ow percentage of siloxane) depending on the ratio of monomers polymerized. Synthetic modificat ions of these initial materials will be discussed as outlined in Table 2. Si SiSi O Si OCH3OCH3OCH3OCH3CH3CH3CH3CH3y x x = 10.1%H2O Si SiSi O Si CH3CH3CH3CH3y xSi SiSi O Si CH3CH3CH3CH3y xO O O OChain-In t e r nal C r osslin k s Chain-Internal Crosslinks Single Elastic Link in Backbone Single Elastic Link in BackboneO O Si Si Si O Si OCH3OCH3OCH3OCH3CH3CH3CH3CH3+[Ru]or[Mo]+Carbosiloxane SOFT Latent Reactive Carbosilane HARD+CH3OH(57) (58) (59) (60) Figure 17. Atmospherically cr osslinked ADMET copolymers 2.1 Synthetically Modified Crosslink Density In an effort to enhance the material prope rties, we initially decided to increase crosslink density by introducing chain-end cross linking. As seen in Figure 17, our initial material crosslinking sites are placed on the hard segment exclusively. Their placement is critical since placing them in the soft se gment would result in the formation of a brittle

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19 material. The chain-end crosslinks woul d produce a higher density while preventing chain end slipping. Figure 18 shows two diffe rent compounds that can be used as chainend crosslinkers, both encompassing di fferent synthetic methodologies. SiOCH3OCH3OCH3x Si x x x CH3(62) (61) Figure 18. Chain-end crosslinking molecules This approach to increase the crosslink density governs two di stinct concepts. First, note that a polymer synthesized using compound 61 (Figure 18) would produce a latent reactive, end-capped linear polymer. On the other hand, compound 62 contains three ADMET active terminal olefins (ƒ = 3) , therefore, using ch ain-end crosslinker 62 will result in a crosslinked network via the ADMET polymerization mechanism. Initially, we focused on proving the chainend crosslinking con cept using monomer 62 , which is an investigation into the effect of crosslinked density on the performance of the polymers. Due to our understand ing of step metathesis, monomer 62 was combined with our previously used monomers (Figure 17). Tripentenylmethylsilane (62) was synthesized by simple Grignard re action of 5-bromo-1-pentene with trichloromethylsilane, which after workup pr oduced an analytically pure trifunctional monomer. ADMET polymerization is a step-growth type of polycondensation, where the initial monomer molar ratios are directly tran sferred to the polymer produced. Also, due to the nature of the substrates polymerize d, all monomers are incorporated randomly in the polymer.

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20 SiOSi CH3CH3CH3CH3y y Si Si OCH3OCH3OCH3OCH3z z+Si x x x CH3+Si Si Si O Si OCH3OCH3OCH3CH3CH3CH3CH3Si CH3m nxy y zOCH3zcat.Si CH3Si CH3z zChain-End Crosslinks Chain-End CrosslinksSi SiSi O Si CH3CH3CH3CH3y xSi SiSi O Si CH3CH3CH3CH3y xO O O OChain-In t e r nal C r osslin k s Chain-Internal Crosslinks Single Elastic Link in Backbone Single Elastic Link in BackboneO O H2O(57) (58) (62) (63) (64) Figure 19. Chain-end cr osslinking in the Polycarbosilanes via ADMET In all cases, the initial rati o of the monomers governs the final polymer produced. As shown in Figure 19, the tripolymer was produced using our initial hard and soft system in combination with crosslinker 62 in a 1:20:1 ratio, respectively. As mentioned earlier, two well-defined ADMET catalyst systems were used; Schrock’s molybdenum catalyst (2) at room temperature or 2nd generation Grubbs’ catalyst (4) at a temperature of 67-70ºC under vacuum. After all the components were thoroughly mixed, the polymerizations were initiated using a 250:1 monomer: catalyst ratio rega rdless of catalyst. Upon initiation, the reaction mixtur e was poured out on a Teflon® plate and placed either in a vacuum desiccator for Schrock’s catalyst (2) , or in a vacuum oven for the secondgeneration Grubbs’ catalyst (4) . In both cases it produces solvent resistant elastic

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21 thermosets before exposure to moisture. This solvent resistance is a direct result of the slight crosslinking produced, us ing the trifunctional monomer 62 . The free-standing film was then exposed to atmospheric moisture to activate our latent crosslinks. The crosslink density of our materials wa s synthetically modified using monomer 65 bearing only two methoxy groups on the si licon atom. The Grignard coupling of 5bromo-1-pentene with tetramethylorthosilicat e after workup and distillation synthesized analytically pure monomer (Figure 20). Si OCH3OCH3MgBr H3COSi OCH3OCH3OCH3+Et2O(65) Figure 20. Synthesis of monomer 65 . Monomer 65 was characterized by both 1H NMR and 13C NMR prior to polymerization. To unsure metathesis compatibility the monomer was homopolymerizaed in the presence of 2nd Generation GrubbsÂ’ catalyst (4) . The spectra for the monomer and resulting ADMET polymer 66 are shown in Figure 21. Indeed, metathesis does occur and can be easily observed by the disappearance of both the internal and external olefins at 5.8 and 5.0 ppm, respectiv ely. Further studies into the copolymerization to produce thermoplas tic elastomer and thermoset are under investigation.

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22 Figure 21. 1H NMR spectra of monomer 65 and its polymer 66 .

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23 2.2 Synthetic Soft Segment Modification Other than crosslink density, the struct ure of the hard and soft components influences the overall mechanical properties of an elastomer. Typically, elastomers are low Tg , essentially amorphous, high molecular we ight polymers. Until now we were using a carbosiloxane-based monomer as the so ft phase of choice due to the inherently low Tg of the Si-O-Si base unit. However, we believe that the single siloxane bond present in the polymer’s repeat unit may not be flexible enough to overcome the large carbon backbone. Synthetically, the most effici ent way to add elastic behavior would be to increase the length of the selected phase and in effect increase both run length and flexibility. As previously reported,32 the homopolymer of monomer 58 has an observed glass transition onset of –91ºC making it a perfect so ft phase. However, the homopolymer and copolymer produced with monomer 58 exhibits only one flexible siloxane bond in the polymer repeat unit. In order to ascertain if this methodology would affect and ultimately improve the mechanical behavior, we initially focused on easily synthesizable soft phase monomers. As a model study, we used the diene vers ion of polyoxyethylene, which has found wide application as soft phase segments.35 The synthesis involv es the reaction of the respective glycol with sodium hydride, fo llowed by the addition of an appropriate bromoalkene.36 The synthesis workup and purification using column chromatography allowed for analytically pure monomers, Figure 22, based on the varying length of polyoxyethylene. These monomers were ch aracterized using nor mal spectroscopic methods.

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24 O O 3 9 9 O O 2 9 9 O O 4 9 9 (67) (69) (68) Figure 22. Soft phase monome rs based on polyoxyethylene. For example, the NMR spectrum for monomer 69 is shown in Figure 23. The characteristic integration of the polyoxyet hylene segment at 3.6 ppm, as well as, the observed resonances for the diene can be seen at 5.8 and 5.0 ppm. Figure 23. 1H NMR spectra of monomer 69

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25 While polyoxyethylene are excellent soft segments; their glass transition is dependent on the number of repeating et hylene oxide units. An increase in Tg is observed with larger numbers of ethylene oxide, Figure 24.37 For example, the small molecule ethylene glycol (n=1) exhibits a Tg = 93ºC while an increase to -50ºC is observed when n=9. Initially, monomer 68 was chosen as the model soft phase due to its low glass transition (-75ºC) relative to monomer 58 (-91ºC). Hopefully, the close proximity of the two Tg s would reduce the effects cause d by the monomers’ molecular differences. The goal in the future is to pr oduce soft phases based solely on siloxane, in effect utilizing the purely amorphous nature of silicon; in fact, the best-known elastomers, polydimethylsiloxane (PDMS), exhibit Tg s as low as -123ºC. H O OHn n Tg (ºC) 1 -93 2 -83 3 -75 4 -70 9 -50 Figure 24. Glass transition temperatures for various lengths of polyoxyethylene Monomer 68 was first homopolymerized with standard bulk polycondensation ADMET conditions in order to check its compatib ility with the catalyst systems. Only a second-generation Grubbs’ catalyst (4) was able to produce a linear polymer having an Mn = 27 770 and PDI = 1.55 after workup. In th e case of Schrock’s molybdenum catalyst (2) , decomposition most likely occurred due to the catalyst’s inability to tolerate oxyphilic or Lewis basic substrates. Ther mal analysis performed on a homopolymer resulted in melting temperatur e at 35.7ºC and a recrystalli zation temperature at 16.6ºC

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26 revealing its semi-crystalline properties. After repeated scanning, both the enthalpy of melting and the enthalpy of recrystall ization exhibit the same energy. Table 3. Mechanical properties of the unsaturated ADMET copolymers and commercially available elastomers. After checking its compatibility with the ADMET polymerization catalyst, we substituted the carbosilo xane soft monomer 58 with monomer 68 (Figure 25). The same 1:20:1 monomer ratio along with the same catalyst loading (250:1) was employed. The resulting polymer exhibited enhanced elastic pr operties relative to the chemistry depicted in Figure 19, even before latent crosslinking in the hard segment was induced. Its tensile strength is included in Table 3 for comparis on to previously made ADMET materials, as well as some commercially available silicon elastomers. A review of Table 3 shows that the mechan ical properties have been characterized for our unsaturated ADMET copolymers as well as for commercially available elastomers. Our previously made thin film 60 , composed only from monomer 58 and 57 exhibits a modulus of 0.16 MPa and 20% el ongation. However, increasing crosslink density by using a chain-end crosslinker 62 , enhances the mechanical properties of this new material (64) . Significant change in the modul us (6 MPa) and elongation (500%) was observed for film 70 , the tripolymer composed fr om the soft phase containing polyoxyethylene (monomer 68 ), and monomer 57 (hard), and a chain-end crosslinker 62 . Collected data in Table 3 supports our inves tigation and predictions for improvement in our previously synthesized material s. Mechanical results for film 70 versus Materials Modulus (MPa) Tensile Strength (MPa) Elongation (%) Material 60 0.16 0.2 20 Material 70 6 0.6 500 “Gelest Zipcone f Series” filler-free fast-cure pure silicone elastomers 2 0.7 150

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27 commercially available elastomers show the advantage of ADMET to synthesize new and better materials while still allowing for polym er modification via or ganic synthesis. Si Si O O OCH3OCH3OCH3OCH3Si9CH33Si Si O O O O Si9CH33Si Si O O O O Si9CH33 H2O xy z x x z z y y AtmosphericO OLonger Length Soft Phase Chain-End Crosslinks Chain-End CrosslinksSi Si O O OCH3OCH3OCH3OCH39 3 9+ + + +CH3OH [Ru](68) (57) (69) (70) Chain-Internal Crosslinks Chain-Internal C r osslin k sSix x xCH3(62) Apply Tension Release Tension Figure 25. High elastic mate rial containing increased soft phase and chain-end crosslinker 2.3 Conclusions ADMET polymerization of carbosilane c ontaining polymers bearing “latent reactive sites", offers a new approach to th e synthesis of materials exhibiting variable physical properties. Increasing crosslink dens ity by using crosslinka ble chain-end groups and increasing the run length of the soft phase, maximizing phase separation and

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28 elasticity. We have demons trated that the crosslink density can be increased by introducing crosslinkable, chain-end groups enhanced our material properties. The resultant film 64 containing a trifunctional ADMET activ e chain-end cro sslinker showed an enhancement in elastic properties. Further, elastic properties of these materials can be modified upon changing run length in the soft phase. Changing a soft phase from the siloxane unit to the polyoxyethylene glycol lead to formation of crosslinked film 70 exhibit good material properties (modulus 6 MPa, elongation 500%).

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29 CHAPTER 3 EXPERIMENTAL METHODS 3.1 General Considerations 1H NMR (300 MHz) and 13C NMR (75 Hz) spectra of the ADMET polymers and monomers were recorded in CDCl3 or C6D6 on either a Mercury series or Varian VXR300 NMR super-conducting spectrometer. Chemical shifts were referenced to residual CHCl3 (7.25 for 1H and 77.23 for 13C). High-resolution mass spectroscopy was performed at the University of Florida facili ty. Elemental analysis was carried out by Atlantic Microlab Inc. (Norcross, GA). Gel permeation chromatography (GPC) of the unsaturated ADMET polymer was performed using two 300 mm Polymer Labor atories gel 5µm mixed-C columns. The instrument consisted of a Rainin SD-300 pump, Hewlett-Packar d 1047-A RI detector (254 nm), TC-45 Eppendorf column heater set to 35 oC, and Waters U6K injector. The solvent used was THF, at a fl ow rate of 1.0 mL/min. Polyme r samples were dissolved in HPLC grade THF (approximately 0.1% w/v) and filtered before injection. Retention times were calibrated to polystyrene sta ndards from Polymer Laboratories (Amherst, MA). Differential scanning calorimetry (DSC) wa s performed using a Perkin-Elmer DSC 7 at a heating rate of 10 C/min. Thermal calibrations were made using indium and freshly distilled n-octane as references for thermal transi tions. Heats of fusion were referenced against indium. The samples we re scanned for multiple cycles to remove

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30 recrystallization differe nces between samples and the resu lts reported are the second scan cycle. Reported values are given as Tm (melting peak). Mechanical tests were performed at the Univ ersity of Florida facility by courtesy of Dr. Brenan’s research group using an Instron model 1122 load frame upgraded with an MTS ReNew system running MTS TestWorks 4 software and a 500 g load cell for the experiments. 3.2 Materials 5-bromo-1-pentene was purchased from Al drich and stored over activated 4Å molecular sieves. 11-bromo-undec-1-ene was purchased from Aldric h and distilled over CaH2. High Purity tetramethylorthosilicate (Ald rich) was used as received. Magnesium turnings (Aldrich) were activat ed by vacuum drying at 100º C. All reagent grade solvents were freshly distilled over a Na/K all oy, except for THF which was dried using Kbenzophenone ketyl. Diethylen e, triethylene, and tetraethy lene glycols (Aldrich) were dried by azeotropic distillation using toluene. Bis(trimethoxysilyl)ethane (Gelest) was dried over CaH2 for 12h under Ar, and distilled before use. All other compounds were used as received. Any necessary chlorosilane s were purchased from Gelest and used as received. Deuterated solvents (Cambridge Isotope Laboratories) were stored over activated 4Å sieves. The metathesis catalysts Cl2Ru(IMes)(PCy3)[=CHPh]38 (4) and [Mo=CHCMe2Ph(=N-C6H3i -Pr2-2,6)(OCMe(CF3)2)2]39 (2) were synthesized according to literature procedures. 3.3 Monomer Synthesis Monomer (57) and (58) were synthesized acco rding to literature.3

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31 3.3.1 Synthesis of tris(4-pen tenyl)methylsilane (62) A 250 mL three-necked round bottom flask equipped with an additional funnel, condenser, and stir bar was flame-dried unde r vacuum, and then flushed with argon. Magnesium turnings (2.1 g, 0.087 mol) and dr y diethyl ether (50 mL) were added. A solution of 5-bromo-1-pentene (11.8 g, 0.08 mol) and 50 mL of diethyl ether was added drop wise to maintain consta nt reflux. After addition, th e mixture was refluxed for an additional hour, followed by cooling to room temperature. Upon cooling, a mixture of trichloromethylsilane (3.32 g, 0.022 mol) in Et2O (10 mL) was added slowly followed by refluxing for 2 hours. The solution was cool ed and the product was diluted with 50 mL of dry pentane and filtered via filter cannulation. The combined organics were evaporated under reduced pressure yieldi ng 6.5 g of a clear, colorless liquid. The crude product was purified by column chromatography us ing straight hexanes. Monomer 62 was collected in 80% and the following spectra l properties were observed: 1H NMR (CDCl3): (ppm) – 0.05 (s, 3H), 0.5 (m, br, 6H), 1.4 (m, br, 6H), 2.05 (m, br, 6H), 5.0 (m, br, 6H), 5.8 (m, br, 3H), 13C NMR (CDCl3): (ppm) –5.25, 13.36, 23.40, 37.79, 114.43, 138.99. EI/HRMS: [M-C5H9]+ calcd. for C11H21Si: 181.1412, found: 181.1412; Elemental analysis Calcd. for C16H30Si: 76.72 C, 12.07 H; found: 76.69 C, 12.18 H. 3.3.2. Synthesis of di(4-pen tenyl)dimethoxysilane (65) A 250 mL three-necked round bottom flask equipped with an additional funnel, condenser, and stir bar was flame-dried under vacuum, and then flushed with argon. Magnesium turnings (2.1 g, 0.087 mol) and dr y diethyl ether (50 mL) were added. A solution of 5-bromo-1-pentene (11.8 g, 0.080 mol) in 50 mL of diethyl ether was added drop wise to maintain consta nt reflux. After addition, th e mixture was refluxed for an additional hour, followed by cooling to room temperature. Upon cooling, the mixture

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32 was filtered via canula into the addition funne l attached to another 250 mL three-necked round bottom flask equipped with condens er, and stir bar. A solution of tetramethylorthosilicate ( 5.44 g, 0.040 mol) in dried Et2O was added followed by dropwise addition of the Grignard reagent. The solution was refluxed for 2 hours, cooled, and the product was diluted with 50 mL of dry pentane and filtered via cannula. The combined organics were evaporated under reduced pressure yielding 5.5 g of a clear, colorless liquid. The crude product was purified by column chromatography using straight hexanes. Monomer 65 was collected in 80% and the following spectral properties were observed: 1H NMR (CDCl3): (ppm) 0.6 (s, 4H), 1.45 (m, br, 4H), 2.05 (m, br, 4H), 3.55 (s, 6H), 5.0 (m , br, 4H), 5.8 (m, br, 2H), 13C NMR (CDCl3): (ppm) 11.61, 22.36, 37.51, 50.55, 115.01, 138.81. EI/HRMS: [M-C5H9]+ calcd. for C12H24SiO2: 181.1412, found: 181.1412; Elemental analysis Calcd. for C16H30Si: 63.14 C, 10.59 H; found: 63.10 C, 10.69 H. 3.3.3 Synthesis of diundecenyl diethylene glycol (67) The synthetic procedure was modi fied from published procedures.40 Sodium hydride (6.5 g, 0.27 mol, 60% dispertion) was placed in a flame-dried, Ar-purged, threenecked 1000 mL round-bottom flask equipped with a stir bar, condenser, and an additional funnel. Dried di ethylene glycol (5.7 g, 0.054 mol) and 260 mL of dry THF were combined in a flame-dried 500 mL Schl enk flask. The solution was transferred to the additional funnel and the mixture was adde d drop wise under cons tant stirring. After 24 h, 11-bromoundecyl-1-ene (30 g, 0.13 mol) in 240 mL of THF was added and stirred for an additional 72 h at reflux. Upon cooling 50 mL of water was added, stirred for 15 minutes, and extracted using ether. The combin ed organic extracts were washed with a saturated NaCl solution, dried over MgSO4, filtered, and evaporated under reduced

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33 pressure. The crude product was then purified by column chromatography using hexanes/diethyl ether (80%:20%) as an eluent . The fractions were concentrated yielding 17 g of monomer 67 . The following spectral pr operties were observed: 1H NMR (CDCl3): (ppm) 1.25 (m, br, 24H), 1.60 (m, br, 4H), 2.10 (m, br, 4H), 3.53 (m, br, 4H), 3.60 (m, br, 8H), 4.95 (m, br, 4H), 5.85 (m, br, 2H); 13C NMR (CDCl3): (ppm) 26.32, 29.15, 29.36, 29.70, 29.77, 29.87, 29.95, 30.10, 30.16, 34.04, 70.31, 70.89, 71.77, 114.32, 139.28. EI/HRMS: [M]+ calcd. for C26H51O3: 411.3838, found: 411.3818; Elemental analysis Calcd. for C26H50O3: 76.04 C, 12.27 H; found: 76.02 C, 12.36 H. 3.3.4 Synthesis of diundecenyltriethylene glycol (68) Monomer 68 was synthesized according to the above procedure for monomer 67 . However, sodium hydride (6.5 g, 0.27 mol, 60% dispertion), triethylene glycol (10 g, 0.068 mol) in 260 mL of dry THF, 11-bromound ecyl-1-ene (40 g, 0.17 mol) in 240 mL of THF were used. Monomer 68 was collected in 80% (24 g). The following spectral properties were observed: 1H NMR (CDCl3): (ppm) 1.25 (m, br, 24H), 1.60 (m, br, 4H), 2.10 (m, br, 4H), 3.53 (m, br, 4H), 3.60 (m, br , 12H), 4.95 (m, br, 4H), 5.85 (m, br, 2H); 13C NMR (CDCl3): (ppm) 26.10, 28.94, 29.14, 29.45, 29.49, 29.51, 29.55, 29.62, 29.66, 33.81, 70.04, 70.64, 71.53, 114.06, 139.18. EI/HRMS: [M]+ calcd. for C28H55O4: 454.4022, found: 455.4121; Elemental analysis Calcd. for C28H55O4: 73.96 C, 11.97 H; found: 73.91 C, 12.18 H. 3.3.5 Synthesis of diundecenyltetraethylene glycol (69) Monomer 69 was synthesized according to the above procedure for monomer 67 . However, sodium hydride (6.5 g, 0.27 mol, 60% dispertion), tetraethyl ene glycol (10.5 g, 0.0543 mol) in 260 mL of dry THF, 11-brom oundecyl-1-ene (30 g, 0.13 mol) in 240 mL of THF were used. Monomer 69 was collected in 82% (22 g). The following spectral

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34 properties were observed: 1H NMR (CDCl3): (ppm) 1.25 (m, br, 24H), 1.60 (m, br, 4H), 2.10 (m, br, 4H), 3.53 (m, br, 4H), 3.60 (m, br , 16H), 4.95 (m, br, 4H), 5.85 (m, br, 2H); 13C NMR (CDCl3): (ppm) 26.31, 29.04, 29.15, 29.35, 29.59, 29.71, 29.75, 29.82, 29.86, 34.01, 70.29, 70.84, 71.77, 114.16, 139.28. EI/HRMS: [M]+ calcd. for C30H59O5: 499.4362, found: 499.4373; Elemental analysis Calcd. for C28H55O4: 72.24 C, 11.72 H; found: 72.45 C, 11.81 H. 3.4 General Metathesis Conditions All monomers used in polymerization were purified and degassed prior to polymerization. All glassware was thoroughl y cleaned and dried under vacuum before use. The polymerizations were initiated in an argon-filled glove box by placing the appropriate amount of monomer followed by either metathesis catalyst. In all cases the monomer: catalyst ratios were 250: 1. The pol ymerizations were carried out in a schlenk reaction tube equipped with a Teflon stir bar. The flask was charged with the monomer, catalyst and slowly stirred for 2 minutes. Th e reaction tube was sealed using a Kontes Teflon valve and placed on a high vacuum line (<0.01 mm Hg). Initially, an intermediate vacuum was applied until the mixture became viscous. The reaction flask was then placed in a 40º C oil bath and high vacuum. The temperature was gradually raised to 70º C and the reaction was left for 72 h. After th at time the reaction was stopped and the polymer was dissolved in toluen e and precipitated in acetone. 3.4.1 Polymerization of di(4-pentenyl)dimethoxysilane (65) The monomer was polymerized using the above procedure. Monomer 65 (1 g, 0.004 mol) was added to Grubbs’ 2nd generation catalyst (4) (15 mg, 1.7x10-5 mol). The following properties were observed: 1H NMR (CDCl3): (ppm) 0.6 (m, br, 4H), 1.4 (m,

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35 br, 4H), 2.10 (m, br, 4H), 3.53 (m, br, 6H), 5.4 (br, 2H); 13C NMR (CDCl3): (ppm) 11.69, 23.00, 36.41, 50.49, 130.05. 3.4.2 Polymerization of diundece nyltriethylene glycol (68) The monomer was polymerized using the above procedure. Monomer 68 (0.5 g, 0.002 mol) was added to Grubbs’ 2nd generation catalyst (4) (7.3 mg, 8.6x10-6 mol). The following properties were observed: 1H NMR (CDCl3): (ppm) 1.25 (m, br, 24H), 1.60 (m, br, 4H), 2.10 (m, br, 4H), 3.53 (m, br , 4H), 3.60 (m, br, 12H), 5.56 (br, 2H); 13C NMR (CDCl3): (ppm) 25.91, 26.06, 27.17, 28.96, 29.10, 29.16, 29.31, 29.43, 29.46, 29.60, 29.73, 32.49, 32.57, 70.01, 70.57, 70.58, 71.50, 130.30. GPC data (THF vs. polystyrene standards): Mn = 27 770 g/mol; P.D.I. (Mw/Mn) = 1.55. DSC Results: Tm (peak) = 35.7ºC, h = 86.8 J/g; Recrystallization Trecl. = 20.1ºC, h = -88.8 J/g 3.4.3 Tripolymerization of monomers 57, 58, and 62 To produce copolymer 63 , a mixture of monomers 57, 58, and 62 were prepared in a dry-box under an Ar atmosphere. Copolymer 63 was prepared using 1: 20: 1 monomer ratios. Monomer 57 (0.17 g, 5.0 x 10-4 mol), monomer 58 (3 g, 0.01 mol) and monomer 62 (0.13 g, 5.2 x 10-4 mol). The monomers were stirred for 5 minutes to ensure a homogenous mixture before the addition of either 2nd generation Grubbs’ catalyst (4) (0.037 g, 4.41 x 10-5 mol), or Schrock’s catalyst (2) (0.034 g, 4.41 x 10-4 mol). The reaction mixture was stirred under vacuum fo r 10 minutes. However, instead of long reaction times, the polymerization mixture was poured out on a Teflon® plate and placed in a vacuum oven at 70ºC for 72 h. Rigorous bubbling of the ethylene gas was observed, followed by formation of a thin film. After 72 h the Teflon® plate was removed from a vacuum oven and exposed to the atmosphe ric moisture. If Schrock’s catalyst (2) is preferred, the reaction mixture can be poured out onto the Teflon® plate in a glove box.

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36 The Teflon® plate should be placed in a vacuum de ssicator, then removed from the glove box, and placed on a high vacuum line at room temperature for 72 h. After that time the thin film was exposed to the atmospheric moisture. 3.4.4 Tripolymerization of monomers 57, 68, and 62 The monomers mixture was prepared as mentioned above. Copolymer 69 was prepared by mixing monomer 57 (0.11 g, 3.3 x 10-4 mol), monomer 68 (3 g, 6.6 x 10-3 mol), and monomer 62 (0.086 g, 3.46 x 10-4 mol) resulting in 1: 20: 1 monomer ratios. Following the procedure as for copolymer 63 , all monomers were mixed and stirred prior to the addition of the catalyst. In this case 2nd generation Grubbs’ catalyst (4) (0.035 g, 4.1 x 10-5 mol) was used. The r eaction mixture was stirred, sealed, removed from the glove box, and placed for 5-10 minutes on a high vacuum line. After that the reaction mixture was transferred to the Teflon® plate and placed in a vacuum oven at 70ºC. After 72 h, the Teflon® plate was removed and the thin f ilm was exposed to the atmospheric moisture.

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41 BIOGRAPHICAL SKETCH Piotr Pawe Mat oka was born on May 14, 1976, to Maria and Stanis aw Mat oka, in Gniezno, Poland, where he spent 19 years. After graduation from high school in 1995, he successfully passed his chemistry qualifie r, and was accepted to the Department of Chemistry at the University of Adam Mickiewicz, Poznan. In the fall of 1997, he joined Professor Marciniec’s research group. Under his supervision, Piotr conducted research in the field of organosilicon synthesis via metath esis and silylative couplings. In June 2000, he defended his thesis “Chemistry investigation of vinyl-, allyltris ubstitutedsilanes with ally-, vinyl-alkyl ethers catalyzed by ruthenium comp lexes” and graduated with Departmental Honors with a Mast er of Science. That summ er he got married, and that same year he left Poland and attended gradua te school at the Univer sity of Florida under the direction of Professor Kenneth Wagener. Piotr’s work there involved the synthesis of latent reactive carbosilane/carbosiloxane elastomers via acyclic diene metathesis (ADMET).