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-indene) (PIB-b-PInd) arms radiating from hexamethylcyclohexasiloxane (D) cores were prepared, characterized, and their properties investigated. The syntheses of these star-blocks involved the linking by hydrosilation of PInd-b-PIBCH2CHCH2 prearms to D. The prearms were obtained by initiating the living polymerization of Ind by the cumyl chloride (CumCl)/TiCl4 or cumyl methoxide (CumOMe)/TiCl4 systems, continuing by the sequential block copolymerization of IB, and concluding the synthesis by end quenching with allyltrimethylsilane (ATMS). Dedicated experiments were carried out to develop conditions for the various synthesis steps. Select mechanical, thermal, and rheological properties of TPE star-blocks having 5–18 PInd-b-PIB arms have been investigated. Because of the high Tg of the glassy PInd segment (Tg,PInd = 170–220°C), these TPEs maintained their strength at higher temperatures than those of similar polystyrene-based star blocks.