Hydroxyethyl Group Effect on Properties of Bis[(trifluoromethyl)sulfonyl]imide-Type Ionic Liquids

1-Propyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C 3 mim][NTf 2 ]), 1-propyl-1-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide ([C 3 C 1 pyr][NTf 2 ]), 1-hydroxyethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C 2 OHmim][NTf 2 ]), and N -hydroxyethyl- N -methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide ([C 2 OHC 1 pyr][NTf 2 ]) hydrophobic ionic liquids (ILs) were synthesized. The basic properties including density, dynamic viscosity, electrical conductivity, refractive index, decomposition temperature, and molar heat capacity of the four pure ILs were determined by traditional methods. The basic properties of the hydroxyethyl-type functional ionic liquids (FILs) were also compared with the common ILs and other type FILs. According to the linear equation, the density and refractive index were discussed. The data of electrical conductivity and dynamic viscosity were processed by the Vogel–Fulcher–Tamman and Arrhenius equations, and the activation energies of dynamic viscosity and electrical conductivity were obtained by both above-mentioned equations. The Walden rule was used for describing the relationship of density, dynamic viscosity, and electrical conductivity for ILs. The decomposition temperature and molar heat capacity were also determined and discussed in the studied temperature range.