Complexes of Cationic Polymers and Anionic Surfactants

Abstract

Measurements of relative viscosity (Saybolt) and shear dependent viscosity (Haake) were made on solutions containing 1% of a cationic cellulose ether polymer with various ratios of added sodium dodecyl-sulfate (SDS). By contrast with results previously obtained with 0.1% polymer solutions, evidence is found for inter- rather than intramolecular interaction which is brought about by polymer bound surfactant ions. The intermolecular interaction manifests itself as high solution viscosity at low SDS to polymer ratios. At high concentrations of SDS, viz., beyond the region where precipitates of polymer and surfactant form, the results are consistent with a polymer chain associated with many surfactant micelles in a globular structure. The viscosity, in this range, is much lower. Shear dependent rheology was found useful in distinguishing between chain extension and the formation of intermolecular polymer/micelle structures. The latter are favored at low shear. However, the rheology observed shows that chain extension in fact is favored under certain conditions. Small angle neutron scattering results provided information which is consistent with these rheology interpretations.