Viscometric Investigation of Complexes between Polyethyleneoxide and Surfactant Micelles

Abstract

Nonionic polymers in aqueous solutions may associate with surfactant micelles to form polymer-micelle complexes. In this work, the polymer-micelle association is examined by viscometrically monitoring the conformational changes induced in the polymer. Polyethylene oxide with a flexible backbone and dextran with a rigid backbone have been examined in solutions of anionic, cationic, and nonionic surfactants. It is found that no polymer-micelle association takes place in case of dextran. For polyethylene oxide, the extent of polymer-micelle association is large for anionic micelles and small for cationic micelles. It decreases with increasing bulkiness of the surfactant head group. We conclude that the physical factors governing the polyethylene oxidemicelle association are (i) the extent of augmented shielding from water provided by the polymer segments to the hydrocarbon core of the micelles and (ii) the steric and electrostatic interactions between the polymer segments and the surfactant head group at the micellar surface. For these reasons, polymer-micelle complex formation is not favored if the polymers have rigid backbones, if the surfactants have bulky head groups, or if the polarity of the surfactant head group is similar to that of the polymer.