Solubilization of n-alkylbenzenes into octaethylene glycol mono-n-tetradecyl ether (C14E8) micelles

Solubilization of benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-pentylbenzene into the micelles of octaethylene glycol monotetradecyl ether (C(14)E(8)) was studied, where equilibrium concentrations of all the solubilizates were determined spectrophotometrically at 298.2, 303.2, and 308.2 K. The concentration of the above solubilizates except benzene remained constant below the critical micelle concentration (cmc) and increased linearly with an increase in C(14)E(8) concentration above the cmc, whereas benzene concentration was found to remain constant over the whole concentration range of C(14)E(8). The Gibbs energy change (DeltaG(0)) for their solubilization was evaluated by the partitioning of the solubilizates between the aqueous phase and the micellar phase because of the large aggregation number of the C(14)E(8) micelle. Furthermore, enthalpy and entropy changes for their solubilization were evaluated from the temperature dependence of the DeltaG(0) values. From these thermodynamical parameters and the change in absorption spectra of the solubilizates due to their incorporation into the micelles, the solubilization site was found to move into the inner core of the micelle with increasing alkyl chain length of the solubilizates.