Viscoelastic Properties of Homogeneous Triblock Copolymers of Styrene/alpha-Methyl Styrene and Their Polyblends with Homopolymers.

摘要

Seven triblock copolymers of styrene/alpha-methyl styrene were prepared via anionic polymerization. Two types of block structures, ASA and SAS, were made. By the use of Time Temperature Superposition Principle, stress relaxation isotherms of these block copolymers were readily shifted into smooth viscoelastic master curves. The shift factor data of all the block copolymers follow the classical WLF equation. Loss tangent data obtained by dynamic mechanical measurements show only one glass transition in each of these block copolymers, thus indicating the homogeneous nature of these materials. From the master curves, maximum relaxation times were determined by Procedure X method of Tobolsky and Murakami. These maximum relaxation times were found to vary as a function of copolymer composition and block structure.