Solubilization Equilibrium Constants of Synthetic Perfumes in the Micellar Solutions of Nonionic Surfactants

The solubilization of synthetic perfumecompounds {2 -phenylethyl alcohol (PEA), benzyl acetate (BA), d-limonene (LN)} by four kinds of nonionic surfactant {hexadecylpolyoxyethylene ether (C16POEn ; n=10, 20, 30, 40)} was investigated in terms of the measurements of solubilization equilibrium constants and micellar diameter. The solubilization equilibrium constants of the perfume compounds decrease with POE chain length of the surfactants and/or the HLB number of the perfume compounds. The activity coefficient of PEA in C16POEn micelles is appre ciably smaller than those of the other perfumes and is 0.1-0.2. The number of the surfactant required to solubilize one perfume molecule (parameter 2B) is ; for LN, 0. 7-1. 0, for BA, O. 4-1. 0 for PEA, 1.7-2.8. Furthermore, the diameter of C16 POEn micelles increases with increasing amount of the solubilized PEA. These results show that PEA molecule would adsorb more strongly to the POE chains in the micellar hydrophilic region than LN and BA molecules, resulting in the dehydration of the POE chains.