Thermodynamic analysis of the phase equilibrium of the polystyrene-poly(vinyl methyl ether) system

The phase diagrams of polystyrene (PS)-poly(vinyl methyl ether) (PVME) system obtained via optical interferometry in the study of polymer interdiffusion are presented. The influence of molecular weight of the PS on the position of the binodal curve dome and the critical point is shown. Paired interaction parameters and their temperature dependences are calculated in the framework of Flory-Huggins theory both for the present experimental diagrams and for the ones, previously obtained by different authors. It is shown that the generalized temperature dependence of the Flory-Huggins parameter can be used to model phase equilibrium in a wide range of temperatures and compositions. For the first time for PS-PVME system, the generalized phase state diagram characterized by both lower and upper critical solution temperatures is calculated and constructed.

Automated summary

The phase diagrams of PS-PVME system obtained through optical interferometry were presented, showing the influence of PS molecular weight on the position of the binodal curve dome and the critical point. Interaction parameters and their temperature dependences were calculated within the framework of Flory-Huggins theory, demonstrating the utility of the generalized temperature dependence of the parameter for modeling phase equilibrium. The generalized phase state diagram for the PS-PVME system, including both lower and upper critical solution temperatures, was calculated and constructed for the first time.