Ionic liquids effect on critical micelle concentration of SDS: Conductivity, fluorescence and NMR studies

The effects of ionic liquids (ILs) 3-methyl-1-pentylimidazolium bromide, [C5mim][Br] and 1-heptyl-3-methylimidazolium bromide, [C7mim][Br] on the physicochemical properties of aqueous sodium dodecylsulfate (SDS) solutions were studied. Various micellar parameters such as critical micelle concentration (cmc), degree of counter ion dissociation (α), aggregation number (Nagg) as well as some thermodynamic parameters such as standard free energy of micellization ( Δ G m 0 ), standard enthalpy of micellization ( Δ H m 0 ) and standard entropy of micellization ( Δ S m 0 ) have been evaluated. Significant increase in cmc and decrease in counter ion binding along with decrease in Nagg was observed. 1H NMR technique was applied to reveal the solubilization site of ILs in the SDS micellar solutions.