An Alpha-Methylstyrene Isoprene Block Copolymer

Abstract

Considerable interest has been generated during the last few years by the development of styrene-butadiene-styrene (SBS) block copolymers. These polymers were found to be two phase systems, with two glass transition temperatures and with properties closely resembling those of crosslinked filled elastomers. The two glass transition temperatures are almost identical with those of the individual blocks, i.e., −80 and +90°C. Above the glass transition temperature of the hard segments, block polymers lose their mechanical properties.,This work discusses an attempt to replace the polystyrene with poly-α-methylstyrene in these block copolymers. The literature reports different glass transition temperatures for poly-α-methylstyrene. Values as high as 184°C were measured in our laboratories. The purpose of this work is to utilize this high glass transition temperature to obtain a thermoplastic elastomer with a high use temperature. According to Holdenl,2 SBS block copolymers can be prepared by living anionic polymerization.