Densities and apparent molar volumes of diluent solutions of [EmimNTf2], [BmimNTf2], and [BmmimNTf2] in DEGDME and TEGDME

Abstract

The densities of six diluents with molality of 0.0199to 0.5070 mol·kg−1 were measured at atmospheric pressure from 293.15 to 328.15 K. The studied ionic liquids (ILs) include 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([Emim][NTf2]), 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([Bmim][NTf2]), and 1-butyl-2,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([Bmmim][NTf2]). The solvents include diethylene glycol dimethyl ether (DEGDME) and tetraethylene glycol dimethyl ether (TEGDME). The measured densities were applied for calculation of VÐΦ/m3·mol-1 (apparent molar volume) from 293.15 K to 328.15 K. The influence of the introduction of methylene (–CH2-), methyl (–CH3) groups, and the structure of solvents on the density, apparent molar volume were discussed in depth. Redlich-Rosenfeld-Meyer (RRM) equation was used to fit VÐΦ/m3·mol-1 dependence on the molality of the six studied diluent solutions. Two parameter of VÐΦo/m3·mol-1 (infinite dilution apparent molar volume) and EÐΦ0/m3·mol-1·K-1 (limiting apparent molar expansibility) were also been fitted and discussed based on the RRM equation and polynomial equation, respectively. Besides, the interactions of ion-ion and ion–solvent were discussed according to the fitted parameters. The structure making or breaking were also discussed for IL in solvent.