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Anionic Synthesis of In-Chain and Chain-End Functionalized ANIONIC SYNTHESIS OF IN-CHAIN AND CHAIN-END FUNCTIONALIZED POLYMERS A Dissertation Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Sumana Roy Chowdhury December, 2006 ANIONIC SYNTHESIS OF IN-CHAIN AND CHAIN-END FUNCTIONALIZED POLYMERS Sumana Roy Chowdhury Dissertation Approved: Accepted: _________________________________ _______________________________ Advisor Department Chair Dr. Roderic P. Quirk Dr. Mark D. Foster _________________________________ _______________________________ Committee Member Dean of College Dr. Judit E. Puskas Dr. Frank N. Kelley _________________________________ _______________________________ Committee Member Dean of Graduate School Dr. Frank N. Kelley Dr. George R. Newkome ________________________________ _______________________________ Committee Member Date Dr. Frank W. Harris ________________________________ Committee Member Dr. Chrys Wesdemiotis ii ABSTRACT The objective of this work was to anionically synthesize well-defined polymers having functional groups either at the chain-end or along the polymer chain. General functionalization methods (GFM) were used for synthesizing both kinds of polymers. Chain-end functionalized polymers were synthesized by terminating the anionically synthesized, living polymer chains using chlorodimethylsilane. Hydrosilation reactions were then done between the silyl-hydride groups at the chain-ends and the double bonds of commercially available substituted alkenes. This produced a range of well-defined polymers having the desired functional groups at the chain-ends. In- chain functionalized polymers were synthesized by anionically polymerizing a silyl- hydride functionalized styrene monomer: (4-vinylphenyl)dimethysilane. Polymerizations were done at room temperature in hydrocarbon solvents to produce well-defined polymers. Functional groups were then introduced into the polymer chains by use of hydrosilation reactions done post-polymerization. The functionalized polymers produced were characterized using SEC, 1H and 13C NMR, FTIR, MALDI TOF mass spectrometry and DSC. The monomer reactivity ratios in the copolymerization of styrene with (4- vinylphenyl)dimethylsilane were also measured. A series of copolymerizaions was done with different molar ratios of styrene(S) and (4-vinylphenyl)dimethylsilane(Si). iii Three different methods were used to determine the values of the monomer reactivity ratios : Fineman-Ross, Kelen-Tudos and Error-In-Variable (EVM) methods. The average values of the two monomer reactivity ratios obtained were: rSi = 0.16 and rS = 1.74. From these values it was observed that in the copolymerization of styrene with (4-vinylphenyl)dimethylsilane, the second monomer was preferentially incorporated into the copolymer chain. Also, rSirS = 0.27, which shows that the copolymer has a tendency to have an alternating structure. Amino acid-functionalized polymers (biohybrids) were synthesized by using a simple and efficient, three-step method. The first step was to make a copolymer of styrene with (4-vinylphenyl)dimethylsilane, followed by introduction of amine functional groups into the polymer chain, using a hydrosilation reaction between the silyl-hydride units in the copolymer chain and the double bond of allyl amine. The third step was a condensation reaction between these amine functional groups on the copolymer chain and the carboxyl group on N-carbobenzyloxy-phenylalanine (a protected amino acid). Although this method has been used to incorporate a particular amino acid onto the polymer chain, it maybe possible to extend this procedure to introduce virtually any amino acid or peptide group into the polymer chain. Finally a thermoplastic elastomer (TPE) was synthesized using the monomer (4- vinylphenyl)dimethylsilane. The first block of this TPE was a copolymer block of styrene with (4-vinylphenyl)dimethylsilane, followed by a polyisoprene block and finally another copolymer block of styrene and (4-vinylphenyl)dimethylsilane. This polymer was characterized using SEC, 1H and 13C NMR, FTIR, DSC, DMTA, TEM iv and tensile testing. It was seen to exhibit properties similar to those of a regular styrene-diene-styrene TPE. However, the silyl-hydride units introduced into this polymer chain can be easily converted to different functional groups using hydrosilation reactions. Introduction of such functional groups would be helpful in tailoring the properties of the TPE. v ACKNOWLEDGEMENTS I am deeply grateful to my advisor, Professor Roderic P. Quirk, for his continued support and encouragement during the past few years. I am also very grateful to all my group members (past and present) for their help and also for making my stay here more enjoyable. I also want to thank my parents and my husband, Jayanta, for their support during my stay here. Without their help and encouragement I would not have been able to reach here. vi TABLE OF CONTENTS Page LIST OF FIGURES…………………………………………………………….......xii LIST OF TABLES………………………………………………………………….xvi LIST OF SCHEMES……………………………………………………………….xvii CHAPTER I. INTRODUCTION…………………….…………………………………….…....1 II. HISTORICAL BACKGROUND………………………………………….….....4 2.1 Living Anionic Polymerization…………………………….……………......4 2.1.1 General Aspects………………………………………………….……4 2.1.2 Monomers……………………………………………………….…….7 2.1.3 Solvents…………………………………………………………….....8 2.1.4 Initiators………………………………………………………….……9 2.1.5 Lewis Base Effects……………………………………………….......12 2.1.6 Initiation Reactions………………………………………………......13 2.1.7 Propagation Reactions…………………………………………….....15 2.1.8 Stereochemistry of diene polymerization……….…………………...16 2.2 Copolymerization…………………………………………………………..18 2.2.1 Block Copolymers…………………………………………………...20 2.2.1.1 Three-step sequential monomer addition……………….…..20 vii 2.2.1.2 Two-step monomer sequential addition and coupling………..21 2.2.1.3 Difunctional initiation and two-step monomer addition……...21 2.2.2 Determination of monomer reactivity ratios………………………….22 2.2.2.1 Fineman-Ross Method……………………………………….22 2.2.2.2 Kelen-Tudos Method………………………………………....23 2.2.2.3 Error-In-Variable (EVM) Method……………………………24 2.3 Functionalized Polymers…………………………………………………….24 2.3.1 Chain-end functionalized polymers…………….…………………….25 2.3.1.1 Hydrosilation Reactions…………….………………………..27 2.3.1.2 A General Functionalization Method by combination of anionic polymerization and hydrosilation reaction………….29 2.3.2 In-chain functionalized polymers………………………….…………30 III. EXPERIMENTAL…..…………………………………………………………34 3.1 Purification of Solvents, Monomers and Reagents…………………….…...36 3.1.1 General……………………………..…………………………………36 3.1.2 Hydrocarbon Solvents……………………………..………………….36 3.1.3 Ethers…………………………………………..……………………..37 3.1.4 Alcohols………………………………………………..……………..38 3.1.5 Styrene…………………………………………………..……………38 3.1.6 Isoprene…………………………………………………..…………...39 3.1.7 Chlorodimethylsilane……………………………………...………….39 3.1.8 Allyl functional compounds…………………………………………..39 3.2 Synthesis of (4-vinylphenyl)dimethylsilane……………………………...…39 viii 3.3 Introduction and modification of functional groups post- polymerization………………………………………………………………40 3.3.1 Hydrosilation Reactions………………………………………………40 3.4 Polymerization Techniques………………………………………………….42 3.5 Polymerization Studies……………………………………...………………44 3.5.1 Polystyrene and Poly(4-vinylphenyl)dimethylsilane…….…………..44 3.5.2 Poly(styrene-co-4-(vinylphenyl)dimethylsilane)…………….………46 3.5.3 Polyisoprene………………………………………………….………48 3.6 Synthesis of functional polymers………………………….………….…….48 3.6.1 Silyl-hydride chain-end functional polystyrene………………….…..48 3.6.2 Synthesis of cyanide-end functionalized polystyrene………………..49 3.6.3 Synthesis of ethyl ether, chain-end functionalized polymer……….…49 3.6.4 Synthesis of acetate, chain-end functionalized polymer……………...50 3.6.5 Synthesis of epoxide, in-chain functionalized polymer………………50 3.6.6 Synthesis of diol in-chain functionalized polymer…………………...51 3.6.7 Synthesis of perfluoroalkyl in-chain functionalized polymer………..51 3.6.8 Synthesis of polymer-peptide biohybrid……………………………..52 3.6.8.1 Synthesis of in-chain amine functionalized copolymer……..52 3.6.8.2 Synthesis of the biohybrid…………………………….……..52 3.6.9 Synthesis of the thermoplastic elastomer (TPE) using (4-vinylphenyl)dimethylsilane……………………………….............53 3.7 Polymer Characterization………………..………………………………….54 3.7.1 Molecular Weight and Molecular Weight Distribution……..……….54 ix 3.7.1.1 Size Exclusion Chromatography (SEC)…..…………………54 3.7.1.2 Matrix Assisted Laser Desorption-Ionization Time of Flight (MALDI TOF) Mass Spectroscopy………….…….55 3.7.2 Nuclear Magnetic Resonance (NMR) Spectroscopy………….….…..55 3.7.3 Fourier Transform Infrared Spectroscopy (FT-IR)…………………...56 3.7.4 Thermal Properties of Copolymers…………………………………...56 3.7.4.1 Differential Scanning Calorimetry (DSC)…………………...56 3.7.4.2 Dynamic Mechanical Thermal Analysis (DMTA)……….….56 3.7.4.3 Thermogravimetric Analysis (TGA)………………………...57 3.7.5 Thin Layer Chromatography (TLC)………………………..………...57 3.7.6 Column Chromatography……………………………………………..57 . 3.7.7 Tensile Testing…………………………………………………….….57 3.7.8 Transmission Electron Microscopy (TEM)……………………….….58 3.7.9 Contact Angle Measurements………………………………………...58 3.7.10 Ellipsometry Measurements………………………………………....58 3.7.11 Compression Molding……………………………………………….59 IV. RESULTS AND DISCUSSION………………………………………….……60 4.1 Synthesis of chain-end functionalized polystyrene……………………….…60 4.1.1 Synthesis of cyanide-functionalized polystyrene…………………......60 4.1.2 Synthesis of ethyl-ether terminated polystyrene………………….…..74
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