Physical properties of isobutylene based block copolymers

Physical, mechanical and thermal properties of a new class of isobutylene based model block copolymers are studied and contrasted with those of traditional thermoplastic elastomers based on polydienes and saturated polydienes (polyolefins) such as Kraton (or Vector) and Kraton G block copolymers. Melt state rheological and dynamic mechanical measurements confirm that thermodynamic interactions between polystyrene (S) and polyisobutylene (iB) or poly‐p‐tert‐butylstyrene (tbS) and iB are comparable to, if not larger than, those between S and polybutadiene (B) or S and ethylene/butene‐1 copolymer (EB). Physical properties for the S‐iB‐S and tbS‐iB‐tbS block copolymers, particularly the injection‐moldability and cut‐growth characteristics, are found to be considerably different from those found for the S‐B‐S and S‐EB‐S systems. We attribute this behavior to the longer entanglement chain length of iB compared with those for B and EB.