A conductometric investigation of hydroxypropylmethyl cellulose/sodium dodecyl sulfate/nonionic surfactant systems

Abstract

Surfactant mixtures are very often used in various cosmetic and pharmaceutical products because they commonly act in synergism and provide more favorable properties than a single surfactant. Simultaneously, the presence of polymers in mixtures of surfactants may lead to molecular interactions and thereby affecting product stability and activity. For these reasons, it is very important to determine the influence of surfactant interactions on micellization and mixed micellization, as well as polymer-surfactant mixed micelles interactions. In this study, the self-aggregation of nonionic surfactants, polysorbate 20 (Tween 20), polyoxyethylene octylphenyl ether (Triton X100) and polyoxyethylene-polyoxypropylene block copolymer (Pluronic F68), with an ionic surfactant, sodium dodecyl sulfate, was examined in aqueous solution at 40 °C using a conductometric titration method. It was found that the concentration region for mixed micelle formation depends on the characteristics of the nonionic surfactant and its concentration. The formation of mixed micelles of surfactants in the presence of a nonionic polymer, hydroxypropylmethyl cellulose, and their binding to the hydrophobic sites of the polymer were also investigated. An analysis of obtained results indicated to different kinds of interactions in the investigated systems, which are crucial for their application.