Phase behavior of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide with chloroform and/or chloroform/carbon tetrachloride mixed solvent

Abstract

The phase behavior of liquid mixtures of the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C2MIM][NTf2]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C4MIM][NTf2]), 1-pentyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C5MIM][NTf2]) with chloroform and chloroform/carbon tetrachloride mixed solvent including the effect of deuterium substitution in chloroform has been studied. Using the cloud point method the phase diagrams were obtained showing very complicated miscibility behavior. Thus phase diagrams with the upper critical solution temperature (UCST) were obtained in most cases however under some conditions the phase diagrams with the lower critical solution temperature (LCST) or even with the both (UCST and LCST) were also observed. The “hourglass” type of the phase diagrams constitutes another type of the phase behavior observed in this study. Deuterium substitution affects the miscibility very seriously, in particular in the systems with the mixed solvent (CHCl3/CCl4). In general the worse miscibility is observed, and deuteration induces large isotope shifts of the UCST and LCST, provoking in some cases the transfer from the UCST/LCST behavior to the “hourglass” phase diagram.