Interfacial tensions of imidazolium-based ionic liquids with water and n-alkanes

The interfacial tension of the liquid-liquid phase boundary of several 1,3-dialkyl imidazolium based ionic liquids, namely, 1,3-dimethylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C₁mim][NTf₂], 1-ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C₂mim][NTf₂], 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C₄mim][NTf₂], 1-hexyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C6mim][NTf2], 1-octyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide [C8mim][NTf2], 1-butyl-3-methylimidazolium trifluoromethylsul-fonate [C₄mim][CF₃SO₃], and 1-butyl-3-methylimidazolium trifluoroacetate [C₄mim][CF₃COO] with water and with the n-alkanes, n-hexane, n-octane and n-decane, has been measured using the pendant drop method as a function of temperature from 293 to 323 K. The experimental interfacial tension data were correlated using the ionic liquid parachor estimation method and a mutual solubility model. The influence of the cation and anion of ionic liquids and also of alkyl chain length of n-alkanes on interfacial tension is discussed. It has also been demonstrated that the interfacial tension data estimated by the correlation methods are in good agreement with the experimental data.