Polyisobutylene based thermoplastic elastomers: VI. Poly(#alpha#-methylstyrene-b-isobutylene-b-#alpha#-methylstyrene) triblock copolymers by coupling ofliving poly(#alpha#-methylstyrene-b-isobutylene) diblock copolymers

摘要

Poly(#alpha#-methylstyrene-b-isobutylene-b-#alpha#methylstyrene) (P#alpha#MeSt-PIB-P#alpha#MePSt) triblock copolymers have been prepared via coupling of living diblock copolymers in a one pot procedure. The P#alpha#MeSt-PIB diblock copolymers were synthesized by living sequential cationic polymerization in methylcyclohexane (MeChx)/methylchloride (MeCl) solvent mixtures at -80 deg C using BCl_3 for #alpha#MeSt polymerization and TiCl_4 for IB polymerization as coinitiators. The crossover efficiency, however, was only approx57 %, due to intermolecular alkylation (indanyl ring formation) after the additio of TiCl_4. By modifying the P#alpha#MeSt end with a short segment of p-chloro-#alpha#-methylstyrene before IB addition the crossover efficiency was increased to 90 %. Coupling of the living block copolymers with 2,2-bis[4-(1-phenylethenyl)phenyl]propane (BDPEP) was rapid and gave approx90 % efficiency.