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

Abstract

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.

Phase Equilibrium and Interdiffusion in Blends of Polystyrene with Polyacrylates

“…In order to construct the dome of binodal curves, we carried out a thermodynamic analysis of experimental data in accordance with the previously developed and tested method for interpreting the phase state diagrams of amorphous separation [ 18 , 29 ]. At the first stage of the analysis of the diagrams by Equation (1) and the coexisting phase compositions, the values of the Flory–Huggins parameter χ were estimated under the assumption of the absence of its concentration dependence.…”

“…= 632.8 nm) was used as a light source. Methods of processing of the interferograms, interdiffusion zones, and phase diagrams construction did not differ from those described earlier [27][28][29].…”

“…All measurements were carried out on an ODA-2 IPCE diffusiometer (IPCE RAS, Moscow, Russia) [ 27 ] in the temperature range from 300 to 440 K. A helium-neon laser (λ = 632.8 nm) was used as a light source. Methods of processing of the interferograms, interdiffusion zones, and phase diagrams construction did not differ from those described earlier [ 27 , 28 , 29 ].…”

“…However, it was not possible to experimentally determine the position of the critical temperature for most systems, since for them the UCST is higher than the temperature of thermal destruction (T d ). In order to construct the dome of binodal curves, we carried out a thermodynamic analysis of experimental data in accordance with the previously developed and tested method for interpreting the phase state diagrams of amorphous separation [18,29].…”

“…• At the first stage of the analysis of the diagrams by Equation ( 1) and the coexisting phase compositions, the values of the Flory-Huggins parameter χ were estimated under the assumption of the absence of its concentration dependence. In order to construct the dome of binodal curves, we carried out a thermodynamic analysis of experimental data in accordance with the previously developed and tested method for interpreting the phase state diagrams of amorphous separation [18,29].…”