Study of the Complexation of Sodium Dodecyl Sulfate with Cationically Charged Acrylamide and N-Isopropylacrylamide Based Copolymers: the Role of the Polymer Chain Hydrophobicity and of Its Charge Density

Abstract

The complexation of sodium dodecyl sulfate with statistical copolymers of the cationically charged (3-(methacryloylamino)propyl)trimethylammonium chloride with acrylamide and N-isopropylacrylamide has been studied. Conformational changes of the macromolecular coil in the aqueous surfactant solutions were monitored through the measurement of the reduced viscosity of the polymer in these solutions. The formation of polymer−surfactant hydrophobic aggregates was detected by steady-state fluorescence measurements, while their concentration was determined by time-resolved fluorescence quenching measurements. The amount of the surfactant adsorbed onto the copolymer was obtained by equilibrium dialysis experiments. Moreover, combining the results of the two last techniques, we have estimated the aggregation number and the microviscosity of the polymer−surfactant aggregates. The degree of binding was calculated and the influence of the Donnan effect on the results obtained was estimated. Finally, interesting conclusions on the role of the polymer hydrophobicity and of its charge density on the formation of these polymer−surfactant complexes were extracted.