Phase Equilibria of Quasi-Ternary Systems Consisting of Multicomponent Polymers in a Binary Solvent Mixture IV. Spinodal Curve and Critical Solution Point

Abstract

An attempt was made to construct a quasi-ternary system consisting of multicomponent polymers dissolved in binary solvent mixture (solvents 1 and 2) to derive the equations of spinodal and neutral equilibrium conditions and to clarify the effects of three thermodynamic interaction χ-parameters between solvent 1 and solvent 2, solvent 1 and polymer, and solvent 2 and polymer(χ12, χ13, and χ23) and the weight-average degree of polymerization Xw0 and the ratio of Xw0 to the number-average degree of polymerization Xn0 of the original polymer on the spinodal curve and the critical points (the critical concentration vpc) calculated from the above mentioned equations. The cloud point curve was also calculated indirectly from coexisting curve evaluated according to a method in our previous papers and constant vps (starting polymer volume fraction) line. The cross point of a constant vps line and a coexisting curve is a cloud point. The cloud point curve thus calculated was confirmed to coincide, as theory predicted with the spinodal curve, at the critical point. vpc decreases with an increase in χ12, χ23 and Xw0, and increases with an increase in χ13 and Xw0/Xn0.