A series of 1-alkyl-4-methyl-1,2,4-triazolium ionic liquids have been synthesized and their physicochemical and thermal properties are reported. Two structural variables were considered as part of this study: alkyl chain length and counteranion. For each series, temperature-dependent properties such as viscosity, conductivity and density were determined and a Walden plot analysis was completed in order to determine their ‘ionicity’. In general, viscosity was found to increase with increasing alkyl chain length while density and molar conductivity were found to decrease. Larger, non-coordinating organic anions [OTf] and [NTf2] exhibited the lowest viscosities while [NTf2] and [BF4] displayed the best conductivities (given the same alkyl chain length). All of the ionic liquids exhibited ‘good’ behavior according to the Walden plot although poorer performance was observed for ionic liquids utilizing the iodide [I] or tosylate [OTs] anion. Short-term, temperature-ramped TGA experiments indicated no correlation between Tonset or Td5% and alkyl chain length, however long-term, isothermal TGA studies indicated a general increase in T0.01/10 (temperature at which 1 % of the IL decomposes in 10 hours) and activation energy of decomposition as the alkyl chain length increased. Weakly coordinating counteranions such as [NTf2] and [OTf] exhibited the most promising thermal stability (short- and long-term). Overall, the TGA studies indicated that the 1,2,4-triazolium ionic liquids were not as thermally stable as the model imidazolium ionic liquid [bmim][NTf2].

Physicochemical and thermal properties of 1,2,4-triazolium ionic liquids

249th National Meeting (2015)

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