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, EMP+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 H-1 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.