Probing the self-aggregation of ionic liquids in aqueous solutions using density and speed of sound data

The aggregation behavior of three 1-alkyl-3-methylimidazolium chloride ionic liquids, [CnC1im]Cl (with n = 8, 10, 12), was probed at atmospheric pressure using density and speed of sound measurements in the 283.15 > T/K > 313.15 temperature range in aqueous solutions with mole fraction ranges of 0 > x([C8C1im]Cl) > 58 · 10−4, 0 > x([C10C1im]Cl) > 20 · 10−4, and 0 > x([C12C1im]Cl) > 4.8 · 10−4. The results were used to calculate partial molar volumetric data and the isentropic compressibility of the solutions, both of which can be used as relevant properties to probe aggregate formation. In this context, micelle formation, solvation phenomena and water structural changes within the solutions are discussed in terms of the temperature and concentration dependence of the calculated properties.

► Three diluted ionic liquid aqueous solutions were analyzed. ► Density and speed-of-sound data were obtained in the 283.15 > T/K > 313.15 range. ► The partial molar volumes and isentropic compressibility were calculated. ► The formation of micelles was probed and discussed considering those properties.