Polyisobutylene-Based Thermoplastic Elastomers. II. Synthesis and Characterization of Poly(p-Methylstyrene-block-isobutylene-block-p-Methylstyrene) Triblock Copolymers

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Abstract
The synthesis of poly(p-methylstyrene)–polyisobutylene–poly(p-methylstyrene) triblock copolymer was accomplished by sequential monomer addition. The synthesis involves the living polymerization of isobutylene by the TiCl4/methylchloride:hexanes, 40:60 v:v/ −80°C system in the presence of di-tert-butylpyridine using di- or trifunctional initiator. When the polymerization of isobutylene is complete, the living polyisobutylene chain end is converted to the corresponding diphenyl alkyl end by capping with 1,1-diphenyl ethylene. Subsequently, titanium(IV)-isopropoxide is added to decrease the Lewis acidity and p-methylstyrene is introduced. The best triblocks exhibited ∼22 MPa tensile strength.