The efficiency of solubilization in mixed micelles of nonionic and anionic surfactants

Abstract

The dependency of water-isoluble and slightly soluble dyes on the composition of nonionic hydrocarbon-anionic hydrocarbon and of nonionic hydrocarbon-amionic fluorocarbon surfactants in micelles has been studied through the solubilization characteristics of these dyes. Yellow OB as a water-insoluble dye and azobenzene as a slightly water-soluble dye were used. According to the regular solution theory, the composition of surfactants in mixed micelles and their concentrations were calculated from the critical micelle concentration of the mixed surfactant systems. The ideal solubilized amounts for mixed micelles were also calculated from solubilizing power, and compositions of mixed micelles with different concentrations. From the comparisons of ideal and observed solubilized amounts, the following results were obtained. (1) The efficiency of solubilization decreased when two surfactants were mixed. The extent of the efficiency depends on the kinds of mixed surfactant systems and dyes, and the efficiency of solubilization has a minimum at 0.2–0.4 molar fraction of nonionic surfactant in the mixed micelles. (2) The efficiency of solubilization decreased with an increase in the difference of the solubilizing power between two surfactants in the mixed systems.