Thermal properties of alkyl-triethylammonium bis {(trifluoromethyl)sulfonyl}imide ionic liquids

Abstract In this work, we address the thermal properties of selected members of a homologous series of alkyltriethylammonium bis {(trifluoromethyl)sulfonyl}imide ionic liquids. Their phase and glass transition behavior, as well as their standard isobaric heat capacities at 298.15 K, were studied using differential scanning calorimetry (DSC), whereas their decomposition temperature was determined by thermal gravimetry analysis. DSC was further used to measure standard molar heat capacities of the studied ionic liquids and standard molar heat capacity as a function of temperature for hexyltriethylammonium, octyltriethylammonium, and dodecyltriethylammonium bis {(trifluoromethyl)sulfonyl}-imide ionic liquids. Based on the data obtained, we discuss the influence of the alkyl chain length of the cation on the studied ionic liquids on the measured properties. Using viscosity data obtained in a previous work, the liquid fragility of the ionic liquids is then discussed. Viscosity data were correlated by the VTF equation using a robust regression along a gnostic influence function. In this way, more reliable VTF model parameters were obtained than in our previous work and a good estimate of the liquid fragility of the ionic liquids was made. © Springer Science+Business Media New York 2015.