New telechelic polymers and sequential copolymers by polyfunctional <i>ini</i>tiator‐trans<i>fer</i> agents (inifers). III. Synthesis and characterization of poly(α‐methylstyrene‐<i>b</i>‐isobutylene‐<i>b</i>‐α‐methylstyrene)

Abstract

Abstract 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 Et 2 AlCl 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 M n calculated from M n of Cl‐PIB‐Cl and triblock overall composition is in excellent agreement with experimental M n 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.