Complex Formation and Ionic Association in Methanol Solutions of Poly(Ethylene Oxide) and Alkaline Earth Salts

Abstract

Abstract Complex formation of poly(ethylene oxide) (PEO) with divalent barium and strontium salts was investigated in methanol. In these systems the complexation was accompanied by a considerable degree of ionic association. An analytical model for the polymer-ion complexation based on a one-dimensional lattice model was proposed. According to this model, the electrostatic effects between the bound ions were separated from the total free energy change of the binding. Three binding constants, i.e., the ionic association constant K A, the cation binding constant, K c, and the anion binding constant, K a, could be estimated. K A for barium and strontium salts was comparable, and the effect of counteranions on K A was not large. K c for barium salts was almost independent of the kind of counteranion and larger than that for corresponding strontium salts, indicating stronger polymer-ion interaction for barium salts. The anion binding constant, K a, was strongly dependent upon the kind of anion, and the order w...