Effect of Homopolymer Molecular Weight on Order-Order Transition in Block Copolymer and Homopolymer Blends

Abstract

The order-order transition temperature (T-OOT) in blends of poly(styrene-b-isoprene-b-styrene) (S-I-S) triblock copolymer and polyisoprene (PI) homopolymer was investigated by using synchrotron small-angle X-ray scattering (SAXS). Pure triblock copolymer undergoes an order-order transition (OOT) from hexagonally ordered cylinder (HEX) to body centered cubic (BCC) phases. In order to investigate the effect of the molecular weight of the added homopolymer on T-OOT of the triblock copolymer, various low-molecular-weight PI homopolymers were studied. The results revealed that T-OOT was affected by the PI molecular weight. T-OOT was reduced for blends having low-molecular-weight PI.