Calculation of phase diagram of polymer solution over supercritical fluid region based on the Patterson-Delmas theory of corresponding state

Based on the Patterson-Delmas theory of corresponding state and the equation of state by Flory, the polymer–solvent interaction parameter χ1 in the Flory–Huggins theory has been calculated over a temperature range including the supercritical fluid region of solvent and a wide range of pressure up to 1.0×104 bar. The temperature dependence of χ1 parameter at constant pressure over the supercritical fluid region is expressed by a parabolic-like with a maximum, and a closed-loop phase diagram is calculated in nonpolar polymer solution by the Flory–Huggins theory and the temperature dependence of χ1 parameter in this work.