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

The complexation of sodium dodecyl sulfate with statistical copolymers of t he cationically charged (3-(methacryloylamino)propyl)trimethylammonium chlo ride with acrylamide and N-isopropylacrylamide has been studied. Conformati onal changes of the macromolecular coil in the aqueous surfactant solutions were monitored through the measurement of the reduced viscosity of the pol ymer in these solutions. The formation of polymer-surfactant hydrophobic ag gregates was detected by steady-state fluorescence measurements while their concentration was determined by time-resolved fluorescence quenching measu rements. The amount of the surfactant adsorbed onto the copolymer was obtai ned 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 obtain ed was estimated. Finally, interesting conclusions on the role of the polym er hydrophobicity and of its charge density on the formation of these polym er-surfactant complexes were extracted.