Solubilization of Oil Soluble Azo Dye by Anionic-Nonionic Mixed Surfactants in Aqueous Solution

Abstract

The solubilization of oil soluble azo dyes by anionic-nonionic mixed surfactants was studied by spectrophotometric methods : these systems are sodium dodecyl sulfate (SDS) -alkyl polyoxyethylene ethers (C_mPOE_n; m=12, 14, 16, and 18, n=10, 20, 30, and 40). The limit of solubilization and solubilizing power by pure C_mPOE_n solutions were exceeded those by pure SDS solution. The influence on the limit of solubilization and solubilizing power was due to greater difference in hydrophobic groups in nonionic surfactants than in hydrophilic groups. When the two surfactants were mixed, the limit of solubilization increased with alkyl chain length in the nonionic surfactant. With increasing oxyethylene groups in the chain, however, the solubilization remained essentially constant. The amount of increase was larger in the system in which two kinds of rich-micelles exist than in a system of mixed micelles. The presence of the oil soluble azo dye resulted in the formation of a mixed micelle.