Thermodynamic and aggregation behavior of aqueous tetradecyltrimethylammonium bromide in the presence of the hydrophobic ionic liquid 3-methyl-1-pentylimidazolium hexafluorophosphate

The micellization behavior of the cationic surfactant, tetradecyltrimethylammonium bromide (TTAB) with the ionic liquid (IL) 3-methyl-1-pentylimidazolium hexafluorophosphate [C(5)mim][PF6] has been investigated using conductometric and spectroscopic techniques. Addition of different wt.% of [C(5)mim][PF6] to aqueous TTAB solution results in an increase in cmc as well as a decrease in aggregation number (N-agg). The cmc and degree of counterion dissociation (alpha) of the aqueous solution of TTAB containing different amounts of [C(5)mim][PF6] have been determined at various temperatures by means of electrical conductivity. The two popular solvatochromic fluorescence probes pyrene and pyrene-1-carboxaldehyde have been used in order to confirm cmc and to calculate N-agg. The preferential site of localization of IL molecules in TTAB micelles was assessed using H-1 NMR spectroscopy. In general, [C(5)mim][PF6] shows an inhibitory effect on the formation of micelles of TTAB and leads to an increase in cmc. The results obtained through conductance measurements are well supported by spectral studies, viz, fluorescence and NMR. (C) 2015 Elsevier B.V. All rights reserved.