Solubilization of Some Synthetic Perfumes by Anionic-Nonionic Mixed Surfactant Systems. 1

Abstract

The solubilization of synthetic perfumes (eugenol, linalool, benzyl acetate, α-ionone, α-hexylcinnamaldehyde, and d-limonene) by sodium dodecyl sulfate (SDS)/hexadecyl poly(oxyethylene) ethers (C 16 POE 20 ) mixed surfactants has been studied by measurement of the maximum additive concentration (MAC) and the distribution coefficient between the micellar and bulk phase (K). The MAC of the perfume at any mole fraction of C 16 POE 20 increases with the hydrophilicity of the perfume. The MAC of the more hydrophilic perfume in the mixed systems is smaller than the calculated MAC (assuming additivity) because of hydrophilic-hydrophilic interactions between the head groups of anionic and nonionic surfactants in the mixed micelle. On the other hand, the radius of the mixed micelle in these systems is large compared to the radii of pure component micelles, causing the MAC values of the less hydrophilic perfumes in the mixed systems to be larger than the calculated MAC. Moreover, the values ofKfor each perfume in the mixture ofthe surfactants are smaller than the ideal K values ; this effect increases with a decrease in the hydrophilicity of the perfume, except in the case of d-limonene. The magnitude of these changes in K values in the surfactant mixtures depends on the relative importance of surfactant-surfactant and surfactant-perfume interactions.