Thermodynamic properties and interfacial behaviour of uncharged polymers and binary polymer mixtures

Abstract

The thermodynamic properties of uncharged polymers in aqueous solution and the interfacial behaviour of single polymer and binary polymer mixtures, respectively, on colloidal dispersions of negatively charged polystyrene latex were studied. The water activities in binary and ternary solutions of chemically different polymers were determined by a gel-deswelling method and the relevant solvent–segment and segment–segment pair interaction parameters were calculated. In aqueous dispersions of polystyrene latex, with and without adsorbed polymer, respectively, the osmotic pressures were directly measured by a block osmometer and the corresponding solvent activities were estimated. Independent adsorption isotherms were determined for each polymer, both individually and under simultaneous, competitive adsorption conditions. As a measure of the preferential affinity for particle surfaces of chemically different macromolecules in simultaneous competitive adsorption, preferential adsorption parameters for the polymers in pairs were used. The thermodynamic characteristics proved to be relevant indicators for the interfacial behaviour of the polymers. Correlation was found between the thermodynamic activity and the affinity for polystyrene surfaces of the polymeric adsorbates.

Acknowledgement: The Hungarian Science Foundation under grant OTKA T 034929 supported this work.