Miscibility in Random Copolymer Blends

Compatibility in homopolymer-copolymer and copolymer-copolymer mixtures may be enhanced by the repulsion of dissimilar segments in the random copolymer chain. A mean field approach for this phenomenon is presented that gives a quantitative description of this phenomenon and that accounts for many of the phenomena observed. It can also be used to derive segmental interaction parameters from miscibility measurements. The treatment is generalized to cover other situations: (a) homopolymers with copolymers containing a common segment, (b) copolymer-copolymer blends in which the blend constituents contain the same two segments but in differing ratios, and (c) copolymer-copolymer blends containing one common segment. Graphical representatives of model calculations for several of these systems are shown.