Transport properties of binary solutions containing the ionic liquid BMI.BF4 and ethylene glycol

Abstract

The ionic conductivity values of the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) and ethylene glycol (EG) electrolytes in different concentrations and over a wide temperature range were determined. The results are discussed in terms of the interactions between the cations and anions of the ionic liquid and the organic solvent. The temperaturedependence of the ionic conductivity for BMI.BF4, as well as solutions containing BMI.BF4 and EG as electrolytes, in the temperature range of 248-358 K, obeys the Vogel-Tammann-Fulcher equation. The highest ionic conductivity was 42 mS cm-1 obtained with a solution of BMI.BF4 in EG at a molar fraction of 0.50 (358 K) due to the high ionic mobility. The critical micellar concentration (cmc) of 0.1 mol L-1 determined through the ionic conductivity indicates that BMI.BF4 behaves as a weak electrolyte above this value. The results obtained indicate that binary solutions based on BMI.BF4 and EG are appropriate for use in technological applications, such as capacitors.