142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

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42 B. Charleux, R. Faust Scheme 7 ylstyrene (CMS). An alternate method to obtain initiating sites along a PIB backbone involves the copolymerization with p-MeS followed by selective bromination [59]. The first method has been used by Nuyken and coworkers [60] to synthesize poly[IB-co-CMS-g-2-methyl-2-oxazoline]. The poly(IB-co-CMS) copolymers were synthesized by cationic copolymerization of IB with CMS in CH 2Cl 2 at –80 °C. The preferred coinitiator was BCl 3 since ionization of the chloromethyl group, which could also act as an initiating site, is negligible in conjunction with BCl 3. The polymerization of 2-methyl-2-oxazoline using poly(IB-co-CMS) was considered to proceed according to Scheme 7. All products were soluble in water, indicating the formation of the graft copolymer and the absence of ungrafted macroinitiator. Dialysis of the product also revealed the absence of low MW (
Synthesis of Branched Polymers by Cationic Polymerization 43 promoter (in order to accelerate the initiation step) in the presence of tetrahydrothiophene as a nucleophile. The graft copolymer obtained therefrom had M n =105,000 g mol –1 with broad MWD (M w /M n =2.5) and the authors stated that better defined polymers could be prepared by improving the initiating system. 3.1.2.2 Poly(silyl vinyl ether) Branches Triflated poly(methyl phenyl silylene) Aldol group transfer polymerization of tert-butyldimethylsilyl vinyl ether [62] was initiated by pendant aldehyde functions incorporated along a poly(methyl methacrylate) (PMMA) backbone [63]. This backbone was a random copolymer prepared by group transfer polymerization of methyl methacrylate (MMA) and acetal protected 5-methacryloxy valeraldehyde. After deprotection of the aldehyde initiating group, polymerization proceeded by activation with zinc halide in THF at room temperature. The reaction led to a graft copolymer with PMMA backbone and poly(silyl vinyl ether) or, upon hydrolysis of the tert-butyldimethylsilyl groups, poly(vinyl alcohol) branches. 3.1.2.3 Poly(isobutylene) Branches Grafting IB from PS backbone containing tert-benzylic acetate initiating sites was described by Jiang and Fréchet [64]. The backbone was obtained by chemical modification of PS shown in Scheme 8. Polymerization of IB from the PS macroinitiator was accomplished with BCl 3 as coinitiator in CH 2Cl 2 at –78 °C. Due to the living nature of the polymerization of IB, high grafting efficiencies (~85%) were reported. The resulting ~15% homoPIB was most probably due to initiation from adventitious moisture or direct initiation (haloboration). A similar multifunctional macroinitiator was obtained by Puskas [65] in a radical copolymerization of S and 4-(1-hydroxy-1-methylethyl)styrene. The macroinitiator was then used to initiate the living cationic polymerization of IB. With relatively short backbone and 8–23 branches with M n =10,000– 20,000 g mol –1 , starlike structures, spherical in shape were obtained. The structure was verified by core destruction followed by SEC analysis of the surviving arms.
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Page 3 and 4: Branched Polymers I Volume Editor:
Page 5 and 6: Volume Editor Dr. Jacques Roovers I
Page 7 and 8: Preface While books have been writt
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Poly(macromonomers): Homo- and Copo
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Author Index Volumes 101-142 Author
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Author IndexVolumes 101-142 231 Dun
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Author Index Volumes 101-142 233 Ka
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Author Index Volumes 101-142 235 Og
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Author Index Volumes 101-142 237 Su
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Subject Index Addition-fragmentatio
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Subject Index 241 Microphases 11z,
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