Diffusion and Thermodynamics of Mixing of Polystyrene with Statistical Copolymers of Butyl Acrylate and Styrene

Interdiffusion and phase equilibrium in the system composed of polystyrene and statistical copolymers of butyl acrylate and styrene were studied by optical interferometry. The diagrams of the phase state were for the first time plotted and analyzed; pair interaction parameters were determined. The obtained diagrams are characterized by an upper critical solution temperature (UCST). The dependence of the interaction parameter on copolymer composition, polystyrene molecular weight, and temperature was shown. The data of interdiffusion of polystyrene into copolymers (and vice versa) are presented; they vary within 10–7–10–11 cm2/s. The activation energy of diffusion was calculated. No influence of structural heterogeneity of macromolecules of statistical copolymers on phase characteristics, translational diffusion coefficients, and coordinate of the diffusion front was registered.