Influence of polar solvent on the thermal conductivity of ionic liquid based on the developed two-wire 3ω method

Thermal conductivity plays a critical role in the screening and designing of ionic liquids (ILs) with good thermoelectric performance. With the newly developed two-wire 3ω method proven to eliminate the end effect by introducing a reference wire to the traditional 3ω method, the influence of additional polar solvents (water, ethylene glycol and ethanol) and temperature on the thermal conductivity of three ILs (1-ethyl-3-methylimidazolium dicyanoamide, 1-butyl-3-methylimidazolium dicyanamide and 1-butyl-3-methylimidazolium trifluoromethansulfonate) are investigated. It shows that the thermal conductivity of the three ILs can be reduced by the polar solvents with lower thermal conductivity. The negative temperature dependence of the thermal conductivity of three ILs is changed to be positive by water and weakened by ethylene glycol, but hardly affected by ethanol which also exhibits the negative trend. Experimental thermal conductivities are correlated by the second-order Scheffé polynomial with the average absolute relative deviations lower than 1.9%.