Analytical Sciences

Abstract − Analytical Sciences, 24(10), 1285 (2008).

Aggregation of Imidazolium Ionic Liquids in Molecular Liquids Studied by Small-Angle Neutron Scattering and NMR
Toshiyuki TAKAMUKU,* Yusuke HONDA,* Kenta FUJII,* and Shigeharu KITTAKA**
*Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
**Department of Chemistry, Faculty of Science, Okayama University of Science, 1-1 Ridaicho, Okayama 700-0005, Japan
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.