Phase equilibrium and mixing thermodynamics of polystyrene with copolymers of styrene and methyl methacrylate

Abstract Data on the solubility of oligomer polystyrene and random copolymers of styrene and methyl methacrylate with different styrene contents have been obtained. Phase diagrams were constructed and the values of critical points were determined. The upper critical solution temperature is localized in the temperature range above 420 K and grows with increasing molecular weight of PS and decreasing styrene content in the copolymer. Based on the compositions of the coexisting phases, paired interaction parameters were calculated and their temperature dependences were plotted. The dependence of the interaction parameter on the copolymer composition and the correlation dependence between its enthalpy and entropy components were constructed. A method for simulation phase equilibrium for copolymers of arbitrary composition and molecular weight is proposed.