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Structure of styrene–butadiene–styrene block copolymers by diffusion analysis

1977; Wiley; Volume: 15; Issue: 11 Linguagem: Inglês

10.1002/pol.1977.180151105

1542-9385

Kwan T. Chiang, Michael V. Sefton,

Block Copolymer Self-Assembly

Abstract In this study, solvent sorption was used to investigate the morphology of a styrene–butadiene–styrene (SBS) triblock copolymer. The sorption process was found to deviate from the normal Fickian character, usually found in conventional elastomer–solvent systems, because of the presence of an interfacial region for both polybutadiene and polystyrene. This interphase absorbed solvent at a temperature below its glass transition and contributed to the resulting non‐Fickian time‐dependent diffusion process. The equilibrium diffusion coefficient was estimated to be 3.2 × 10 −7 cm 2 /sec regardless of the casting surface. Nevertheless, according to the sorption measurements, the casting surface did have an effect on the approach to equilibrium. The results indicated a denser packing of the molecules and hence a decreased diffusion coefficient for Teflon and glass cast films, because of internal stresses left within the films during casting.