Multiarm-star polyisobutylenes by living carbocationic polymerization

✍ Scribed by Judit E. Puskas; Christopher J. Wilds

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 208 KB
• Volume: 36
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19980115)36:1<85::aid-pola12>3.0.co;2-9

✦ Synopsis

This article describes the synthesis of high molecular weight multiarm-star branched polyisobutylenes by living polymerization, using multifunctional initiators, and their initial characterization. First, macrointiators carrying tert-hydroxy functionalities were synthesized by the radical copolymerization of 4-(1-hydroxy-1-methylethyl)styrene with styrene. This copolymerization system was found to be ideal with r 1 å r 2 å 1. Selected macroinitiators with average functionalities of 8-73 were then used to synthesize the star-branched polyisobutylenes. Polymers with molecular weights up to M V n Å 400,000 were obtained within 30-60-min reaction times, while under similar conditions the monofunctional 2-chloro-2,4,4-trimethylpentane initiator yielded M V n É 10,000 in 20 min. This can be viewed as an indirect proof that simultaneous multiple initiation took place with the macroinitiators. Under controlled conditions a branched polyisobutylene with M V n Å 375,000 and MWD Å 1.2, and theoretically calculated 23 arms, with no detectable side products was obtained under living conditions in 60 min; the molecular weight of this polymer increased linearly with time. The branched structure of the polymers were demonstrated by SEC-LLS analysis and core destruction of selected samples.