Micellization Thermodynamics of Some Imidazolium Ionic Liquids in Aqueous Solutions—Conductometric Study

Conductances of the aqueous solutions of the ionic liquids, ILs, [1-alkyl-3-methylimidazolium chloride [CnMim]Cl and [1-alkyl-3-methylimidazolium bromide [CnMim]Br (n = 9 and 10) have been measured at 288.15, 293.15, 298.15, 303.15, 308.15 and 313.15 K. Critical micelle concentrations (CMCs) were determined from the conductance data. Concentration dependence of the specific conductance is discussed and the limiting equivalent conductance of the ionic liquids was determined and discussed. To define which temperature range should be investigated for the thermodynamic parameters, the Krafft temperature of each IL was investigated. The ionization degree and the thermodynamic parameters (∆Gm0, ∆Hm0, ∆Sm0) of the micelle formation were also estimated and discussed. The dependency of the CMC on the length of the alkyl chain of the investigated 1-alkyl-3-methylimidazolium ILs was also studied. It is shown that the CMC is directly related to the lipophilicity of the cation.