New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). III. Synthesis and characterization of poly(α‐methylstyrene‐b‐isobutylene‐b‐α‐methylstyrene)

The synthesis of a new glassy‐rubbery‐glassy triblock copolymer poly(α‐methylstyrene‐b‐isobutylene‐b‐α‐methylstyrene) has been demonstrated. The key to the synthesis was the preparation by inifer method of a perfectly bifunctional polyisobutylene which carries tert‐chlorine end groups Cl‐PIB‐Cl. In conjunction with Et2AlCl coinitiator, the telechelic Cl‐PIB‐Cl molecule initiates the polymerization of α‐methylstyrene at both ends of the prepolymer. Triblock composition can be controlled by the judicious selection of synthesis conditions; that is, Cl‐PIB‐Cl molecular weight, α‐methylstyrene concentration, and solvent polarity. Theoretical triblock Mn calculated from Mn of Cl‐PIB‐Cl and triblock overall composition is in excellent agreement with experimental Mn which indicates negligible homopolymer contamination. Extraction with a series of hydrocarbon solvents reveals broad composition distribution. The stress‐strain profile of a triblock is similar to that of a poly(styrene‐b‐butadiene‐b‐styrene) thermoplastic elastomer of similar composition.