Conductometric and spectroscopic study of interaction of cationic surfactants with 3-methyl-1-pentylimidazolium hexafluorophosphate

This paper outlines the effect on micellar behavior of aqueous solutions of cationic surfactants viz. cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) upon addition of ionic liquid 3-methyl-1-pentylimidazolium hexafluorophosphate [C5mim][PF6]. Important physicochemical properties such as conductance, critical micelle concentration (cmc) and aggregation number (Nagg) are observed to change as [C5mim][PF6] is added to aqueous CTAB/CTAC. The conductivity/concentration data of aqueous solutions of CTAB/CTAC with [C5mim][PF6] were determined in the temperature range 298.15, 308.15, 318.15 K. These data were used to determine cmc as a function of temperature and concentration and to evaluate degree of ionization. Using temperature dependence of cmc, various thermodynamic parameters have been evaluated. Behavior of fluorescence probe, pyrene, confirms the interaction between [C5mim][PF6] and cationic micellar surface. Further, 1H NMR studies in micelle solutions containing [C5mim][PF6] have also been carried out in order to interpret the preferential solubilization site of [C5mim][PF6] on the studied micellar systems.