MEAN FIELD-THEORY OF THE PHASE-BEHAVIOR OF TERNARY BLOCK COPOLYMER-HOMOPOLYMER BLENDS

We have extended and applied the theory of polymer blends developed by Hong and Noolandi to the calculation of phase diagrams of ternary A-b-B/A/B copolymer/homopolymer blends which can undergo microphase and macrophase separation. The approach used a perturbative solution to the modified diffusion equation to calculate the polymer distribution functions and the free energy. For simplicity, we assumed that the microphase is lamellar and calculated the free energy up to fourth order. The main results are phase diagrams for a variety of model systems containing symmetric or asymmetric copolymers mixed with homopolymers of varying molecular weights and for a PS-b-PI/PS/PI mixture. We also compared induced microphase formation in ternary and binary blends. It is particularly interesting in blends containing asymmetric copolymers and/or A and B homopolymers having differing molecular weights.