Liquid phase behavior of hexafluorophosphate ionic liquids with polyhydric alcohols

Liquid–liquid equilibria for hexafluorophosphate ionic liquids with 1-alkyl-3-methylimidazolium family of cations: 1-butyl-3-methylimidazolium, [bmim]+, 1-hexyl-3-methylimidazolium, [hmim]+, 1-octyl-3-methylimidazolium, [omim]+ with polyhydric alcohols: 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol have been measured using the cloud point method. The influence of different characteristics of alcohols and ILs, including cation alkyl chain length, alcohol chain length, and relative position of the both OH groups in alcohol were studied. In general, the same type of the phase behavior is observed in all cases showing upper critical solution temperature but the impact of the above-mentioned factors is highly diversified.

► The longer alkyl chain in imidazolium cation of investigated ionic liquid, the worse miscibility with 1,2-ethanediol.
► Miscibility of [omim][PF6] with (1,ω) diols much worse than with (1,2) diols.
► Miscibility of butanediol isomers with [omim][PF6] is better for the solvent with low dielectric constant.