Effect of the alkyl chain length on the electrical conductivity of six (imidazolium-based ionic liquids + γ-butyrolactone) binary mixtures

• Electrical conductivity of the binary mixtures reaches maximum at xIL ≈ 0.13−0.24.
• System with shortest alkyl chain in IL shifted maximum electrical conductivity to higher IL mole fraction.
• Molar conductivities are higher for [CnC1im][NTf2] comparing to [CnC1C1im][NTf2].
• The most efficient solvation of ionic liquids with shortest alkyl chain with GBL molecules.
• Electrical conductivity, effects of temperature and IL concentration are reflected by the quasi-Arrhenius equation.

Electrical conductivity of six binary liquid mixtures of 1,3-disubstituted and 1,2,3-trisubstituted imidazolium based ionic liquids (ILs) with bis(trifluoromethylsulfonyl)imide anion with γ-butyrolactone (GBL) was measured at temperatures from (293.15 to 323.15) K and at atmospheric pressure (p = 0.1 MPa) over the whole composition range. The effects of the temperature and IL concentration on the electrical conductivity were systematically investigated. Values of the electrical conductivity were correlated using Casteel-Amis and Arrhenius equations. Molar conductivity was calculated and temperature dependance were fitted applying the Vogel-Fulcher-Tammann equation. Several semi-empirical models (quasi-Arrhenius and Bahe-Varela model) were also tested to correlate the electrical conductivity. The effect of the alkyl chain length and the influence of C-2 methylation of the imidazolium cation on the electrical conductivity features of six different binary mixtures were evaluated.