On intermolecular interactions in solutions of polymer blends

Phase diagrams for solutions of blends of a series of homopolymers and random copolymers were obtained and compared with the dependences of the second virial coefficient A2 and intensity of excess light scattering R''90 on the ratio of the polymer concentrations in solution. Mutual solubility of polymers correlates with the values of R''90 and A2: the larger the deviations of these parameters from the corresponding additive values, the lower the thermodynamic compatibility of the polymers. Introduction of a third polymer into a binary blend enhanced interaction between unlike molecules, as manifested by a decrease in deviation of A2 and R''90 from their values predicted with the additivity rule, thus indicating an increased mutual solubility of polymers in the ternary system.