Dynamic light scattering and small-angle neutron scattering studies on the poly(ethylene oxide)/sodium dodecyl sulfate/polystyrene latex system

Dynamic light scattering and small-angle neutron scattering measurements have been performed on aqueous polystyrene latex dispersions with physisorbed polymer, poly(ethylene oxide), in the presence of the surfactant sodium dodecyl sulfate (SDS). Dynamic Light scattering measurements suggested that the polymer layer is partially desorbed at surfactant concentrations close to the critical micelle concentration. At surfactant concentrations above the normal critical micelle concentration, the hydrodynamic thickness increased close to the value in the absence of surfactant. Small-angle neutron scattering measurements suggested that as the normal critical micelle concentration of the surfactant was approached, very thin layers were formed. It was possible to obtain the volume fraction profiles of the adsorbed polymer layer, along with information on the structure of the surfactant micelles. Two types of SDS structures were observed, one corresponding to SDS existing bound to bulk polymer and the other to SDS bound to adsorbed polymer.