The effects of ionic liquids (ILs) 3-methyl-1-pentylimidazolium bromide, [C(5)mim][Br] and 1-heptyl-3-methylimidazolium bromide, [C(7)mim][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 (alpha), aggregation number (N-agg) as well as some thermodynamic parameters such as standard free energy of micellization (Delta G(m)(0)), standard enthalpy of micellization (Delta H-m(0)) and standard entropy of micellization (Delta S-m(0)) have been evaluated. Significant increase in cmc and decrease in counter ion binding along with decrease in N-agg was observed. H-1 NMR technique was applied to reveal the solubilization site of ILs in the SDS micellar solutions. (C) 2014 Elsevier B.V. All rights reserved.