Relationship between Phase Behavior and Conductivity of Imidazolium-Based Ionic Liquids with Dicyanamide Anion

The phase behavior and electrical conductivity of two ionic liquids (ILs) with the same anion (dicyanamide) and different cations (1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium) at different temperatures (including subzero ones) are studied in detail, and the relationship between the phase state and electrical conductivity is shown. It is found that the formation of several crystalline mesophases at temperatures below -10 °C and their successive melting in the range between -10 and 10 °C leads to a curvature of the Arrhenius plot. In this case, two linear sections and an inflection in the temperature dependence of electrical conductivity are interpreted in terms of the phase states of the IL: homogeneous (solid and liquid) and a heterogeneous (mixed) phases, and the activating energy of conductivity E_a(κ) of the solid IL is significantly higher than that of the molten one. The obtained results may be useful in the designing of new electrolytes based on IL used in a wide range of temperatures.