Effects of 1-alkyl-3-methylimidazolium bromide ionic liquids on the micellar properties of [butanediyl-1,4-bis(dimethyldodecylammonium bromide)] gemini surfactant in aqueous solution

Abstract

The micellar properties of the cationic gemini surfactant [butanediyl-1,4-bis (dimethyldodecylammonium bromide)] (12-4-12) were investigated at 298.15 K in the presence of 1-R-3-methylimidazolium bromide ionic liquids (ILs, R = 1-butyl, 1-(1-butyl)-3-methylimidazolium bromide (BuMeImBr); 1-hexyl, 1-(1-hexyl)-3-methylimidazolium bromide (HxMeImBr); and 1-octyl, 1-(1-octyl)-3-methylimidazolium bromide (OcMeImBr)), present as additives. The emphasis was on c(IL) (0.2 to 1 wt%) and the length of R. The following techniques were employed: conductivity, surface tension, UV-Vis, fluorescence spectroscopy of solubilized compounds, and dynamic light scattering (DLS). For the ILs, values of the critical micelle concentration, critical micellar concentration (cmc) of 12-4-12 decreased between 0.2 and 0.8 wt% and then increased at 1 wt%. The increased cmc may be due to the formation of mixed micelles. For (inorganic additive) NaBr, cmc decreased continuously as a function of c(NaBr). Other parameters calculated include those related to the adsorption of the surfactant at solution/air interface, micelle aggregation number, and hydrodynamic radius. ILs behave as electrolyte and cosurfactants based on c(IL).