Association Equilibria Theory of Preferential Adsorption in Systems with Solvent-Solvent and Solvent-Polymer Interactions

The theory of association equilibria is used to derive the amount of preferential adsorption for polymer-mixed solvent systems in which one of the two liquids in the mixed solvent (B) autoassociates and interacts specifically with the polymer and with the other liquid (A). The model takes into account the constants for the association of one molecule of B to one site in A and of one molecule of B to one site in the polymer and also the corresponding constants for the multiple self-association of B for the case where the first B molecule is associated either with A or with the polymer or is free. The theoretical results are applied to the systems poly(alkyl methacrylate)s, alkyl = Me, Et, iBu, in the mixed solvent methanol (B) + 1,4-dioxane (A). The experimental results of these systems can be quantitatively well reproduced by the theory.