PREDICTION AND MANIPULATION OF THE PHASE MORPHOLOGIES OF MULTIPHASE POLYMER BLENDS .1. TERNARY-SYSTEMS

The dispersed phases of a multiphase polymer blend will either form an encapsulation-type phase morphology or the phases will remain separat ely dispersed, depending on which morphology has the lower free energy . We have developed a model to predict phase morphologies of multiphas e polymer blends. Calculations based on the model suggest that interfa cial tensions play the major role in establishing the phase structure of a multiphase system, with a less significant role played by the sur face areas of the dispersed phases. The model further shows that the p hase structure of a multiphase polymer blend can be converted from one type to another by changing the interfacial tensions between one or m ore pairs of the components using interfacially-active agents such as block or graft copolymers. We have applied the model to different tern ary blends of polystyrene, polyethylene, polypropylene and poly(methyl methacrylate), and have compared the predicted morphologies of these blends with experimental results. In each case, the predicted morpholo gies agree with those found experimentally. In addition, we have succe ssfully converted the phase structures of these blends from one type t o another by using interfacially-active block copolymers. (C) 1997 Els evier Science Ltd.