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 degrees C using BCl3 for alpha MeSt polymerization and TiCl4 for IB polymerization as coinitiators. The crossover efficiency, however, was only similar to 57 %, due to intermolecular alkylation (indanyl ring formation) after the addition of TiCl4. 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 similar to 90 % efficiency.