Solubilization of Perfume Compounds by Pure and Mixtures of Surfactants

Abstract

The solubilization of two perfume compounds, 2-phenylethanol (PEA) and benzyl acetate (BA), was studied by using an anionic surfactant (sodium dodecyl sulfate, SDS), a nonionic surfactant (hexadecyl polyoxyethylene ether, C 16POE 20), and mixed anionic-nonionic micelles (SDS/C 16POE 20). In order to study the distribution of perfume compounds between the micelle and bulk phases, the solubilization equilibrium constants (distribution constant) were determined as functions of the intramicellar mole fraction of perfume compounds by using the semi-equilibrium dialysis method. The results of the present study show that (1) two or three surfactant molecules may on the average provide a location for the attachment of a PEA molecule in the single surfactant system, (2) BA molecules presumably bind somewhat more weakly to water and other polar groups in the hydrophilic group region of the single surfactant micelle, and (3) the solubilization equilibrium constants for the mixed surfactant system are smaller than predicted by linear or additive mixing rules applied to the single-component surfactant equilibrium constants, indicating that the compactness of the hydrophilic region of the mixed micelle may reduce the number of solubilization sites for the solutes in the micelle as a result of the hydrophilic interaction between the oxygen atoms of anionic surfactant and the ethylene oxide chains of nonionic surfactant.