• Rohlíček, Jan
• Červinka, Ctirad
• Štejfa, Vojtěch

Abstract

Ionic liquids are widely studied compounds with various potential applications, which are restricted by limited availability and understanding of their properties. Despite being commercially produced in a relatively high purity nowadays, the data on thermodynamic properties of ILs published in the most recent papers still keep large discrepancies. Phase behaviour, heat capacities, and crystal structures are studied in this work for additional eight common ionic liquids based on the 1-ethyl-3-methylimidazolium cation, [C1C2Im], coupled with simple organic or inorganic anions. Special attention is paid for drying of the samples, evaluation of the water content and its impact on the studied properties. All the samples were found to exhibit glass transitions, temperatures of which are determined with respect to the heating rate to simplify comparison with future works. The resulting melting temperatures, fusion enthalpies, and heat capacities are critically compared with the available data from the literature. Yet undescribed complex polymorphic behaviour is detected and resolved for methanesulfonate and dicyanamide salts, [C1C2Im][MeSO3] and [C1C2Im][DCA], respectively. The X-ray powder diffraction analysis for samples melting above the room temperature was performed to support our results. A crystal structure for one of the polymorphs of [C1C2Im][MeSO3] is reported for the first time.

Topics

• impedance spectroscopy
• compound
• phase
• glass
• glass
• drying
• melting temperature