New polyisobutylene stars part XXI - Novel thermoplastic elastomers. III. Synthesis, characterization, and properties of star-block copolymers of poly(indene-b-isobutylene) arms emanating from cyclosiloxane cores

Novel thermoplastic elastomers (TPEs) consisting of poly(isobutylene-b-inde ne) (PIB-b-PInd) arms radiating from hexamethylcyclohexasiloxane (D-6(H)) c ores were prepared, characterized, and their properties investigated. The s yntheses of these star-blocks involved the linking by hydrosilation of PInd -b-PIB-CH2-CH=CH2 prearms to D-6(H). The prearms were obtained by initiatin g the living polymerization of Ind by the cumyl chloride (CumCl)/TiCl4 or c umyl methoxide (CumOMe)/TiCl4 systems, continuing by the sequential block c opolymerization of IB, and concluding the synthesis by end quenching with a llyltrimethylsilane (ATMS). Dedicated experiments were carried out to devel op conditions for the various synthesis steps. Select mechanical, thermal, and rheological properties of TPE star-blocks having 5-18 PInd-b-PIB arms h ave been investigated. Because of the high T-g of the glassy PInd segment ( T-g,T-PInd = 170-220 degrees C), these TPEs maintained their strength at hi gher temperatures than those of similar polystyrene-based star blocks. (C) 2000 John Wiley & Sons, Inc.