THERMOPHYSICAL CHARACTERIZATION OF TWO DIETHYLMETHYLAMMONIUM IONIC LIQUIDS

Density, speed of sound, and derived magnitudes of two diethylmethylammonium ILs against temperature have been studied in this work. The chosen ILs were diethylmethylammonium trifluoromethanesulfonate, [C₂C₂C₁N][OTf], and diethylmethylammonium methanesulfonate [C₂C₂C₁N][MeSO₃]. In order to analyse the influence of water content, saturated and dried samples of these ILs were studied. ILs were dried using a vacuum pump, and the saturation level (28% and 6% in weight for [C₂C₂C₁N][MeSO₃] and [C₂C₂C₁N][OTf], respectively) was achieved by keeping the ILs in an open bottle at ambient temperature. Direct measurements of density and speed of sound were taken with an Anton Paar DSA 5000. Linear equations were used to express the correlation with temperature of both properties and the thermal expansion coefficient, and the adiabatic bulk modulus constant have been obtained using expressions proposed in the bibliography [1-3].

The effect of water content is different on both properties. Thus, the density of the samples slightly increases when water is removed whereas opposite behaviour was found with regard to the speed of sound, which decreases when the water content was completely removed.