Interactions of cationic surfactants with polyvinylpyrrolidone (PVP): Effects of counter ions and temperature

The interactions between the polymer polyvinylpyrrolidone (PVP) and conventional surfactants such as cetyltrimethylammonium chloride (CTACl) and cetyltrimethylammonium bromide (CTABr) were investigated using a conductometric method. The critical micelle concentrations (CMCs), the critical aggregation concentrations (CACs) and degrees of ionization (α) of aqueous solutions of the surfactants and PVP were determined via electrical conductivity measurements at various temperatures. The thermodynamic parameters (Gibbs free energy, enthalpy and entropy) of the surfactants were calculated in the absence and presence of the polymer, and the results were compared to determine the effects of counter ion on the micellization of the surfactants and the energetics of the process. The main goal of this work is to elucidate the various driving forces that lead to complexation between the surfactants and polymer. Electrostatic interactions play a major role in the binding of surfactants to polymers or surfaces in aqueous systems. The strength of the interaction is found to depend on the nature of the surfactant counter ion type. [Display omitted] •CMC values were determined for two surfactants with same length chain but different counter ions.•After polymer(PVP) was added to aqueous solution of surfactant, CAC and C2 values were determined.•Interactions between surfactant-polymer have been investigated using thermodynamic parameters of aggregation.•Properties of counter-ion play an important role in the thermodynamic of aggregation.