Thermophysical properties of 1-ethyl-3-methylimidazolium ethylsulfate and 1-butyl-3-methylimidazolium methylsulfate ionic liquids

Heat capacity, glass-transition, crystallization, and melting temperatures of 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO4]) and 1-butyl-3-methylimidazolium methylsulfate ([Bmim][MeSO4]) ionic liquids (ILs) have been determined by differential scanning calorimetry (DSC). Their thermal stabilities have been analyzed by thermogravimetric analysis (TGA). Given the effect of the heating rate over the decomposition temperatures, isothermal TGA experiments are proposed as a more appropriate method to evaluate the thermal stability of the ILs. Inside the working range (-150 degrees C to 30 degrees C), [Emim][EtSO4] and [Bmim][MeSO4] present a glass-transition temperature of -78.4 degrees C and -91.9 degrees C, respectively. [Bmim][MeSO4] has a melting temperature of -4.1 degrees C. The C, was determined in a working range (10 degrees C to 100 degrees C) where its value increases lineally with temperature.