Phase Equilibria of Quasi-Ternary Systems Consisting of Multicomponent Polymers in a Binary Solvent Mixture II. Role of Initial Concentration and Relative Amount of Polymers Partitioned in Two Phases

An attempt was made to clarify by computer experiments the role of initial “concentration” vpo and relative amounts of polymers, partitioned in two phases at the phase equilibrium of quasi-ternary polymer solutions. For this purpose, a polymer with the Schulz–Zimm type molecular weight distribution (the ratio of the weight-to number-average molar volume of the polymer relative to the molar volume of solvents, Xwo/Xno=2.0 and Xw=300) was employed under the condition of vpo=1×10−15∼0.07 and the relative amount of the polymer in the polymer-rich phase ρp=1/40∼39/40. The phase equilibrium of the quasi-ternary polymer solutions can be approximated with that of the quasi-binary system consisting of multicomponent polymers and a single solvent having the negative concentration dependence of the polymer–solvent interaction parameter χ. As ρp increases, both the phase volume ratio R and the Xw/Xn of the polymer in the polymer-rich phase decrease and then increase after passing through a minimum.