Solubilization of oil—soluble azo dye by anionic—nonionic mixed surfactants in aqueous solutions, II

Abstract

The solubilization of oil-soluble azo dyes by anionic—ninionic mixed surfactants was studied by spectrophotometric methods: these systems are sodium dodecyl sulfate (SDS)—alkyl polyoxyethylene ethers (C m POE n ; m = 10 and 18 at n = 10 and 40 m = 16). This maximum additive concentration and solubilizing capacity of pure C m POE n solutions exceeded those of pure SDS solutions. The influence on the maximum additive concentration and solubilizing capacity was due to a greater difference in hydrophobic groups in nonionic surfactants than in hydrophilic groups. In the mixed surfactant systems, the maximum additive concentrations are made larger by nonionic surfactants including longer alkyl chains and/or longer polyoxyethylene chains. The amount of increase was larger in the system in which two kinds of micelles, one rich in anionic surfactant and the other rich in nonionic surfactant, exist than in system of mixed micelles. The presence of the oil-soluble azo dye asissts the mixed micelle formation.