ADSORPTION OF SDS AND PVP AT THE AIR-WATER-INTERFACE

The technique of specular reflection of neutrons has been used to inve stigate the adsorption from polyvinylpyrrolidone/sodium dodecyl sulpha te (PVP/SDSI) solutions at the air/water interface. Isotopic substitut ion was used to highlight features of the adsorbed layer and to distin guish between solvent and solute in this layer. At low SDS concentrati ons the presence of the polymer causes an increase in the adsorption o f surfactant (at 1 x 10(-4) M SDS, the area per molecule of SDS is 227 Angstrom(2) in the absence of polymer, 100 Angstrom(2) in 0.5% PVP an d 85 Angstrom(2) in 2.0% PVP). On increasing the surfactant concentrat ion this difference is reduced until, at high SDS concentrations, the surface concentration of surfactant is higher in the absence of PVP (a t 0.01 M SDS, the area per SDS molecule is 42 Angstrom(2), 44 Angstrom (2) and 46 Angstrom(2) at 0%, 0.5% and 2.0% PVP respectively).