Correlation between hydrocarbon flexibility and physicochemical properties for cyclohexyl-imidazolium based ionic liquids studied by 1H and 13C NMR

We have synthesized and characterized a series of cyclohexyl-imidazolium based ionic liquids incorporating a bis(trifluoromethanesulfonyl)amide anion. To reveal the characteristic features afforded by a flexible cyclohexyl substituent, the physicochemical properties including densities, shear viscosities, and thermal properties, were measured and compared with the respective n-alkyl-imidazolium ionic liquids. The cyclohexyl-imidazolium ionic liquids showed higher densities, higher shear viscosities, and higher glass transition temperatures than their acyclic counterparts. Using 1H and 13C nuclear magnetic resonance spectra, we also studied the conformational dynamics of these species.