Influence of aquo-organic solvent media on the self-aggregation of sodium dodecyl sulfate (SDS) and its interaction with polyvinylpyrrolidone (PVP)

Abstract

Influence of mixed aquo-organic solvents viz. water-dimethyl sulfoxide (DMSO), water-formamide (FA), water-dioxane (DX), and water-ethylene glycol (EG) on the micellization of sodium dodecylsulfate (SDS) alone and in presence of neutral polymer polyvinyl pyrrolidone (PVP) was studied. Interaction with PVP initially witnessed formation of critical aggregation concentration (CAC) in the favor of formation of induced small micelles of SDS at a concentration lower than the normal critical micelle concentration (CMC), and later found the formation of normal micelles with extended critical micelle concentrations (CMCe) in solution. The SDS-PVP interaction depended on the nature and composition of the mixed solvents. Besides CAC and CMCe, the maximum Gibbs surface excess at the interface (Γ max), the minimum area (A min) of the dissociated amphiphile anion, and enthalpy of micellization (ΔH m 0 ) were also determined. Configurational state of PVP in aquo-organic media was investigated by the methods of viscometry, dynamic light scattering (DLS), and scanning electron microscope (SEM) methods. The [η] and Huggins constant (k H) were considered to ascertain the overall configuration of PVP in solution. The complexes were formed and aggregated at different stages of their molecular composition. The aggregate sizes were determined by DLS, and the surface morphologies in the solvent removed states were examined by SEM. With reference to bulk and interfacial phenomena, polymer-surfactant interaction is thus considered to be important, and the detailed study herein under taken for SDS-PVP combination and PVP alone in mixed aquo-organic solvent media is a new sort of attempt.