Living carbocationic polymerization

Though living anionic polymerization is the most widely used technique for synthesizing many commercially available TPEs based on styrenic block copolymers, living carbocationic polymerization has also been developed in recent years for such purposes [10,11], Polyisobutylene (PlB)-based TPEs, one of the most recently developed classes, are synthesized by living carbocationic polymerization with sequential monomer addition and consists of two basic steps [10] as follows ... 

Section 7.3 will describe tools we developed to synthesize and characterize soft dendritic nanostructured TPE biomaterials via living carbocationic polymerization, and decorate their surfaces with tissue-friendly groups. 

Synthesis of PIB prepolymers. fm-Chlorine-telechelic PIB (Mn=4,000 MVf/Mn 1.09) (7), and an allyl-telechelic PIB (Mn=9,500 Mw/Mn 1.14) (7,8) were prepared by living carbocationic polymerizations. The tert-chlorine ended PIB was quantitatively dehydrochlorinated (9) to -C(CH3)=CH2 terminated polymer. Both olefin-telechelic PIBs were then hydroborated and oxidized (10) to prepare the primary hydroxyl termini. The hydroxyl-telechelic polymers were esterified with methacryloyl chloride to methacrylate-telechelic PIBs, MA-PIB-MA (11). 

Quasi-living Carbocationic Polymerization of Alkyl Vinyl Ethers and Block Copolymer Synthesis... 

Living" carbocationic polymerizations are most difficult to achieve mainly because of chain transfer to monomer and termination processes both of which frequently occur in carbocationic polymerizations. It has recently been demonstrated (JL) that "quasiliving" polymerization of a-methylstyrene (aMeSt) can be achieved by slow and continuous monomer addition and that the number-average molecular weight (Mn) of PaMeSt increases linearly with the weight of added monomer. A theory for quasiliving polymerizations has been developed (2). 

Majoros, I., Nagy, A. and Kennedy,. P. Conventional and Living Carbocationic Polymerizations United. I. A Comprehensive Model and New Diagnostic Method to Probe the Mechanism of Homopolymerizations. Vol. 112, pp. 1-113. 

Surface-initiated Polymerization Using Living Carbocationic Polymerization (LCSIP)... 

Matyjaszewski, K. and M. Sawamoto, Controlled/Living Carbocationic Polymerization, Chap. 4 in Cationic Polymerizations Mechanisms, Synthesis, and Applications, K. Matyjaszerski, ed., Marcel Dekker, New York, 1996. 

This review concerns the synthesis and characterization of octa-arm polyisobutylene (PIB) stars, allyl-terminated octa-arm PIB stars, and octa-arm star blocks by using a novel octafunctional caHx[8]arene-based initiator 1. Scheme 1 shows the structure of 1 and the target architectures. The syntheses were carried out under living carbocationic polymerization conditions. 

R. Faust and J.P. Kennedy, Living carbocationic polymerization. XXI, Kinetic and mechanistic studies of isobutylene polymerization initiated by trimethylpentyl esters of different acids, J. Macromol. Sci.-Chem., 27(6) 649-667,1990. 

As these considerations also apply to initiations of carbocationic polymerizations and to initiations and propagations in living carbocationic polymerizations, the choice of Lewis acids for these purposes can now be designed systematically. 

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