Physicochemical and Thermal Properties for a Series of 1-Alkyl-4-methyl-1,2,4-triazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids

Physicochemical properties and long-term thermal stabilities are reported for a series of 1-alkyl-4-methyl-1,2,4-triazolium [NTf2] ionic liquids, and a Walden plot analysis was conducted in order to determine the ionicity of these materials. In general, viscosities were found to increase with increasing alkyl chain length while densities and molar conductivities were found to decrease. The 1,2,4-triazolium ionic liquids were classified as good ionic liquids after analysis of the Walden plot; however, they did not perform as well as the standard imidazolium ionic liquid [bmim][NTf2]. Thermal properties from DSC and TGA experiments were also completed. 1,2,4-Triazolium ionic liquids with an alkyl chain length of octyl (C8) or less exhibited a single T-8 transition below -70 degrees C; however, the decyl (C10) and dodecyl (C12) systems exhibited a T-m value. No correlation between T-onset or T-d5% and alkyl chain length was observed during short-term, temperature-ramped TGA experiments. However, long-term, isothermal TGA studies indicated a general increase in T-0.01/10 value as the alkyl chain length increased. Both short-and long-term TGA studies indicated that the 1,2,4-triazolium ionic liquids were not as thermally stable as the model imidazolium ionic liquid [bmim][NTf2].