Competitive Adsorption of Sodium Dodecyl Sulfate on Two Polymer Surfaces within Latex Blends

Experiments were performed to determine how the partitioning of surfactant between two different polymer surfaces in a latex is dependent on the nature of the polymers and their relative surface areas. Titrations of individual latices and latex blends with sodium dodecyl sulfate (SDS) were carried out while continuously measuring the conductivity of the latex. Polymers studied were polystyrene, poly(n-butyl methacrylate), poly(methyl methacrylate), and poly(methyl acrylate) and the individual adsorption areas for SDS on these surfaces at saturation, A s, were found to be 44.0, 58.6, 96.0, and 163.3 Å2/molecule, respectively. For blends of these latices, the average adsorption area at saturation was found to be a linear function of the individual polymer surface area fractions in the blend. It was also possible to predict the behavior of a titration of a latex blend based on the individual titrations for the pure latex. These results confirm the hypothesis that SDS adsorption on multiple polymer surfaces at a fixed temperature is determined by the activity of the surfactant in the water phase.