Structural Investigation on the Poly(vinylpyrrolidone)-Water System in the Presence of Sodium Decyl Sulfate and Sodium Decanesulfonate: A Small Angle Neutron Scattering Study

mall angle neutron scattering (SANS) has been used to study the interaction of sodium decyl sulfate (C100S) and sodium decanesulfonate (C10S) with poly(vinylpyrrolidone) (PVP). The measurements were performed on aqueous solutions of C100S and C10S in the presence and absence of PVP. In all ternary systems the polymer concentration was kept constant at I wt%, and the surfactant molal concentration ranged from 0.002 to 0.150 mol kg(-1). The analysis of the collected SANS profiles confirms the absence of any appreciable interaction between PVP and C10S in contrast with what observed for the PVP-C100S-D2O system. In this latter system, in fact, a clear interaction peak in the scattering pattern appears well below the cmc of the surfactant, which suggests a complex formation between PVP and C100S. The preferential interaction of poly(vinylpyrrolidone) toward sodium decyl sulfate with respect to sodium decanesulfonate reflects the difference in the chemical structure of the two surfactants that produces meaningful differences in the values of their cmc and aggregation number, as shown by the results here presented.