Influence of some polymers on micellization behavior of sodium caprylate and cetyl pyridinium chloride

Abstract

Micellization behavior of anionic surfactant sodium caprylate (SCAP) and cationic surfactant cetyl pyridinium chloride (CPC) in presence of polymers (polyvinyl pyrrolidone, Tween-20, Tween-40, Tween-60 and Tween-80) in aqueous solutions has been investigated using conductivity and viscosity measurements at 298.15 K. The critical micellar concentration (CMC), critical aggregation concentration (CAC) and polymer saturation point (PSP) for both the surfactants have been determined in water as well as in aqueous polymer solutions having different concentrations. The CAC values for both the surfactants were found to decrease slightly with increase in polymer concentration whereas PSP values remained almost constant. The degree of ionization (α) and standard free energy of transfer (ΔGot) have been estimated. ΔGot values were found to decrease with increase in polymer concentration. The relative viscosity, ηr, for the above systems has also been determined at 298.15 K in various polymer solutions. The maximum value of ηI/ηI,max (ηI is the interaction viscosity) as a function of R (ratio of concentration of surfactant to that of polymer), shifts towards the lower values of R with the increase in polymer concentration. The results have been discussed in terms of various interactions occurring in these systems.