PHASE-DIAGRAMS FOR BLOCK COPOLYMER HOMOPOLYMER BLENDS EXHIBITING LCSTBEHAVIOR/

We present phase diagrams of binary blends (or mixtures) of a homopoly mer H, with a block copolymer, A-B, in which there is an exothermic in teraction between two types of segments, H and A. In trying to constru ct phase diagrams, we extend the approach of predicting phase separati on behaviour in such binary blends where H is chemically identical wit h one of the blocks of the copolymer, e.g. A. A binary blend of a homo polymer with a block copolymer is divided into two distinct states, i. e, an ordered state and a disordered state. On the assumption that the block copolymer in the disordered state acts as a random copolymer, t he free-energy change in the disordered state can be estimated by a mo del including the localized solubilization of added homopolymers, whic h is a modification of the confined-chain model originated by Meier. T o determine coexisting phases under a given temperature, we examine th e relative stabilities (i.e. the chemical potential of each component in the blend) of the two states. As a result, the concentration-temper ature phase diagrams of blends of H and A-B can be obtained. From the predicted phase diagrams, it is found that the exothermic interaction of this system greatly increases the solubility of H into the A domain s and affects the shape of the phase diagram.