Kinetic Effect on Pressure-Induced Phase Transitions of Room Temperature Ionic Liquid, 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate

Room temperature ionic liquids (RTILs) have intriguing high-pressure phase behavior, and investigation of how pressure affects phase transitions of RTILs might yield interesting results. We here present kinetically driven phase transitions of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][CF3SO3]) at different rates of similar to 0.3 and similar to 1.2 GPa/h up to similar to 5 GPa. Two crystalline phases formed at similar to 1.3 and similar to 1.7 GPa with increasing pressure at lower compression rate of similar to 0.3 GPa/h; however, the amorphous phase solidified with superpressurized glass above similar to 3.3 GPa at higher compression rate of similar to 1.2 GPa/h. Notably, crystal polymorphism is discussed in view of the conformational isomerism of [Emim](+) cation and an unknown cation conformer is observed. These facts indicate that kinetic effect on pressure-induced phase transitions of [Emim][CF3SO3] might be dependent on compression rate, which needs to be considered as a non-negligible factor for phase transitions of RTILs under high pressure.