Phase Equilibrium, Phase Structure, and Interdiffusion in Polystyrene–Polyphenylmethylsiloxane Polymer Mixtures

Comprehensive studies of solubility and diffusion in PS–PPMS systems are performed via optical interferometry, DSC, and SEM. The interdiffusion zones in PS–siloxane oligomer systems are studied for the first time. It is shown that the general tendency of the change in the position of the concentration profile over time is to expand without changing the nature of the dependence. A smooth change in the concentration of the siloxane oligomer in PS is observed in the limits of the solubility region. Generalized state diagrams of PS–polysiloxane systems are constructed. The effect molecular weight has on the position of the branches of the binodal curves is determined. It is shown that the upper critical solution temperature (UCST) grows along with the molecular weight of linear oligomers, while the heterogeneous region expands and the binodal dome shifts to the region of thermal destruction of the compositions. The concentration, temperature, and molecular weight dependences of the diffusion coefficients are determined for each of the studied systems. The apparent activation energies are calculated for diffusion.