Aggregation of Imidazolium Ionic Liquids in Molecular Liquids Studied by Small-Angle Neutron Scattering and NMR

The aggregation of two imidazolium-based ionic liquids, 1-ethly-3-methylimidazolium chloride (EMI+Cl^-) and EMI+ bis- (trifluoromethanesulfonyl)amide (EMI+TFSA^-), in molecular liquids, water, methanol, acetonitrile, and benzene, has been studied by using the small-angle neutron scattering (SANS) technique. The SANS results have shown that the heterogeneity of EMI+Cl^--acetonitrile mixtures is significant at high acetonitrile contents, thus, EMI+Cl^- forms clusters in acetonitrile solutions. On the other hand, it has been revealed that EMI^+Cl^- is homogeneously dissolved in water and methanol. EMI+TFSA^- remarkably aggregates in methanol solutions, while the mixtures of EMI+TFSA^- with acetonitrile and benzene are homogeneous. Furthermore, aggregation of EMI+Cl^- and EMI+TFSA^- in acetonitrile and methanol, respectively, has been examined by using ^1H NMR spectroscopy. The mechanism of aggregation of the ionic liquids in the molecular liquids has been discussed on the basis of the properties of cations, anions, and molecular liquids.

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