ISSN:
0887-624X
Keywords:
thermoplastic elastomers
;
poly (-methylstyrene-b-isobutylene-b--methylstyrene)
;
triblock copolymer
;
living carbocationic polymerization
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Preparatory to triblock synthesis experiments, the cationic polymerization of α-methylstyrene (αMeSt) was investigated using the 2-chloro-2,4,4-trimethylpentane (TMPCI)/TiCl4 initiating system in the presence of triethylamine (Et3N) as electron donor (ED) and CH3Cl/n-hexane mixed solvent in the -80 to -40°C range. Conversions are influenced by temperature, [TiCl4], [Et3N], and [αMeSt]. The polymerization of αMeSt is living at -80°C: Both termination and chain transfer to monomer are frozen out, however, initiation is slow relative to propagation. Highly syndiotactic (〉94%) Pα Mest was obtained. At-60deg;C initiator efficiency is ca. 100%, but termination becomes evident. Et3N may act both as Ed and as proton scavenger. Novel poly(α-methystyrene-b-isobutylene-b-α-methylstyrene) (PαMeSt-PIB-PαMeSt) triblocks have been synthesized by adding αMeSt to biliving polyisobutylene carbocations (⊕PIB⊕) in the -80 to -40°C range. The effects of temperature, solvent polarity, and [Et3N] on the block copolymerization have been investigated. At -80°C, the rate of crossover from ⊕PIB⊕ to αMeSt is lower than that of propagation of PαMeSt⊕, so that the triblock is contaminated by PIB and PIB-b-PαMeSt. At -60°C, crossover occurs preferentially. The rate of propagation relative to that of crossover is also reduced by lowering the solvent polarity and increasing the [Et3N]. High crossover efficiency and blocking efficiency can be obtained under optimum blocking conditions. The triblocks are novel thermoplastic elastomers (TPEs). © 1994 John Wiley & Sons, Inc.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1994.080320301
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