Electrochemical control of solubilization using a ferrocene-modified nonionic surfactant

An investigation was conducted on the control of solubilization making use of changes in the surface properties caused by the electrochemical redox reaction of 11-ferrocenylundecyl polyoxyethylene ether (FPEG), a ferrocene-modified nonionic surfactant, in aqueous solutions. Examinations through surface tension measurement of the effect of the redox reaction of the ferrocenyl group on the critical micelle concentration (cmc) of FPEG showed that the oxidation produces an increase in the cmc from 6×10−6 to 5×10−5 mol l−1 and the re-reduction causes the cmc to decrease from 5×10−5 to 9×10−6 mol l−1. The effect of the redox reaction of the ferrocenyl group was then examined on the solubilization equilibrium constant, K, for solubilization of benzene, ethylbenzene and 2-phenylethylalcohol in FPEG micelles. The equilibrium constant was found for all solubilizates to decrease when the ferrocenyl group is oxidized and increase again if the group is re-reduced, indicating that oxidation of the ferrocenyl group releases portions of the solubilizate from the micelles into the bulk and the re-reduction gives rise to re-solubilization of the released solubilizate.