New combinational models were proposed to predict the phase behavior of vapor–liquid equilibrium of some semidiluted binary polymer solutions at different temperatures. On the basis of these models in a polymer solution a chemical reaction, solvation, was considered producing a complex composition. In addition, the Flory–Huggins theory was applied to account for the difference of molecular volumes, and two segment-based local composition models, NRTL (nonrandom two-liquid) and Wilson, were considered for description of physical interactions between species in solutions. To evaluate the accuracy of these suggested models, a number of experimental data were correlated. It was shown that the results of the proposed models are comparable with experimental data and can predict solvent activity more accurately than the available models.
