Journal of Solution Chemistry

, Volume 42, Issue 10, pp 1888–1901 | Cite as

Small-Angle Neutron Scattering Study on Aggregation of 1-Alkyl-3-methylimidazolium Based Ionic Liquids in Aqueous Solution

  • Takumi Kusano
  • Kenta Fujii
  • Masaaki Tabata
  • Mitsuhiro Shibayama


Aggregation structures of 1-alkyl-3-methylimidazolium based ionic liquids (ILs) in aqueous solution were investigated by small-angle neutron scattering (SANS) from the viewpoint of alkyl chain length, n, and anions (Cl, Br and trifluoromethanesulfonate, \( {\text{CF}}_{3} {\text{SO}}_{3}^{ - } \)). In [C4mIm+]-based IL systems, no noticeable SANS intensity was observed for all of the systems examined here, although aqueous [C4mIm+][\( {\text{BF}}_{4}^{ - } \)] solutions show a significant SANS profile originating from concentration fluctuations in the solution (Almasy et al. J Phys Chem B 112:2382–2387, 2008). This suggests that [C4mIm+][Cl], [C4mIm+][Br] and [C4mIm+][\( {\text{CF}}_{3} {\text{SO}}_{3}^{ - } \)] homogeneously mix with water, unlike the [C4mIm+][\( {\text{BF}}_{4}^{ - } \)] system, due to preferential hydration of the ions. In the case of the C n mIm cations with longer alkyl chain lengths (n = 8 and 12), SANS profiles were clearly observed in the aqueous solutions at IL concentrations of C IL > 230 and 20.0 mmol·dm−3, respectively. For aqueous [C8mIm+][Br] solutions, the asymptotic behavior of the scattering function varied largely from I(q) ~ q −2 to ~q −4 with increasing C IL, indicating that the solution changes from an inhomogeneous mixing state to a nano-scale micelle state. Aqueous [C12mIm+][Br] solutions show a typical SANS profile for micelle formation in solution. It was found from a model-fitting analysis that the structure of the [C12mIm+][Br] micelle is ellipsoidal, not spherical, in solutions over the C IL range examined here.


Ionic liquid Aggregation Micelle formation Small-angle neutron scattering 



This work has been financially supported by Grant-in-Aids for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (No. 24750066 to KF, No. 22245018 to MS). The SANS experiments were performed with the approval of the Institute for Solid State Physics, The University of Tokyo (Proposal No. 8599 and 8847K), at the research reactor, JRR-3, Japan Atomic Energy Agency, Tokai, Japan.

Supplementary material

10953_2013_80_MOESM1_ESM.doc (230 kb)
Supplementary material 1 (DOC 230 kb)


  1. 1.
    Wasserscheid, P., Welton, T. (eds.): Ionic Liquids in Synthesis, 2nd edn. Wiley, Weinheim (2008)Google Scholar
  2. 2.
    Pandey, S.: Analytical applications of room-temperature ionic liquids: a review of recent efforts. Anal. Chim. Acta 556, 38–45 (2006)CrossRefGoogle Scholar
  3. 3.
    Brennecke, J.F., Rogers, R.D., Seddon, K.R. (eds.): Ionic Liquids IV. ACS, Washington, DC (2007)Google Scholar
  4. 4.
    Ohno, H. (ed.): Electrochemical Aspects of Ionic Liquids. Wiley, New York (2005)Google Scholar
  5. 5.
    Huddleston, J.G., Willauer, H.D., Swatloski, R.P., Visser, A.E., Rogers, R.D.: Room temperature ionic liquids as novel media for ‘clean’ liquid–liquid extraction. Chem. Commun. 16, 1765–1766 (1998)CrossRefGoogle Scholar
  6. 6.
    Pádua, A.A.H., Gomes, M.F.C., Lopes, J.N.A.C.: Molecular solutes in ionic liquids: a structural perspective. Acc. Chem. Res. 40, 1087–1096 (2007)CrossRefGoogle Scholar
  7. 7.
    Blanchard, L.A., Hancu, D., Beckman, E.J., Brennecke, J.F.: Green processing using ionic liquids and CO2. Nature 399, 28–29 (1999)CrossRefGoogle Scholar
  8. 8.
    Fujii, K., Ishiguro, S., Umebayashi, Y.: Trends in Ionic Liquid Electrochemistry Research Vibration Spectroscopic Study of Room-Temperature Ionic Liquids—Conformational Isomerism and Metal Ion Solvation, Chap. 5. Nova Science Publishers, Inc., New York (2010)Google Scholar
  9. 9.
    Fujii, K., Asai, H., Ueki, T., Sakai, T., Imaizumi, S., Chung, U., Watanabe, M., Shibayama, M.: High-performance ion gel with tetra-PEG network. Soft Matter 8, 1756–1759 (2012)CrossRefGoogle Scholar
  10. 10.
    Susan, M.A., Kaneko, T., Noda, A., Watanabe, M.: Ion gels prepared by in situ radical polymerization of vinyl monomers in an ionic liquid and their characterization as polymer electrolytes. J. Am. Chem. Soc. 127, 4976–4983 (2005)CrossRefGoogle Scholar
  11. 11.
    Bates, E.D., Mayton, R.D., Ntai, I., Davis Jr, J.H.: CO2 capture by a task-specific ionic liquid. J. Am. Chem. Soc. 124, 926–927 (2002)CrossRefGoogle Scholar
  12. 12.
    Swatloski, R.P., Spear, S.K., Holbrey, J.D., Rogers, R.D.: Dissolution of cellulose with ionic liquids. J. Am. Chem. Soc. 124, 4974–4975 (2002)CrossRefGoogle Scholar
  13. 13.
    Arce, A., Earle, M.J., Katdare, S.P., Rodriguez, H., Seddon, K.R.: Application of mutually immiscible ionic liquids to the separation of aromatic and aliphatic hydrocarbons by liquid extraction: a preliminary approach. Phys. Chem. Chem. Phys. 10, 2538–2542 (2008)CrossRefGoogle Scholar
  14. 14.
    Anderson, J.L., Armstrong, D.W., Wei, G.: Ionic liquids in analytical chemistry. Anal. Chem. 78, 2893–2902 (2006)Google Scholar
  15. 15.
    Villagran, C., Deetlefs, M., Pitner, W.R., Hardacre, C.: Quantification of halide in ionic liquids using ion chromatography. Anal. Chem. 76, 2118–2123 (2004)CrossRefGoogle Scholar
  16. 16.
    Charoenraks, T., Tabata, M., Fujii, K.: A micro-solvent cluster extraction using aqueous mixed solvents of ionic liquid. Anal. Sci. 24, 1239–1244 (2008)CrossRefGoogle Scholar
  17. 17.
    Bandres, I., Meler, S., Giner, B., Cea, P., Lafuente, C.: Aggregation behavior of pyridinium-based ionic liquids in aqueous solution. J. Solution Chem. 38, 1622–1634 (2009)CrossRefGoogle Scholar
  18. 18.
    Kiselev, V.D., Kashaeva, H.A., Shakirova, I.I., Potapova, L.N., Konovalov, A.I.: Solvent effect on the enthalpy of solution and partial molar volume of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. J. Solution Chem. 41, 1375–1387 (2012)CrossRefGoogle Scholar
  19. 19.
    Domanska, U., Krolikowska, M.: Density and viscosity of binary mixtures of thiocyanate ionic liquids+water as a function of temperature. J. Solution Chem. 41, 1422–1445 (2012)CrossRefGoogle Scholar
  20. 20.
    Sastry, N.V., Vaghela, N.M., Macwan, P.M., Soni, S.S., Aswal, V.K., Gibaud, A.: Aggregation behavior of pyridinium based ionic liquids in water: surface tension, 1H NMR chemical shifts, SANS and SAXS measurements. J. Colloid Interface Sci. 371, 52–61 (2012)CrossRefGoogle Scholar
  21. 21.
    El-Dossoki, F.I.: Micellization thermodynamics of some imidazolium ionic liquids in aqueous solutions—conductometric study. J. Solution Chem. 42, 125–135 (2013)CrossRefGoogle Scholar
  22. 22.
    Francois, Y., Zhang, K., Varenne, A., Gareil, P.: New integrated measurement protocol using capillary electrophoresis instrumentation for the determination of viscosity, conductivity and absorbance of ionic liquid–molecular solvent mixtures. Anal. Chim. Acta 562, 164–170 (2006)CrossRefGoogle Scholar
  23. 23.
    Vaghela, N.M., Sastry, V., Aswal, V.K.: Surface active and aggregation behavior of methylimidazolium-based ionic liquids of type [CnmIm][X], n = 4, 6, 8 and [X] = Cl, Br, I in water. Colloid Polym. Sci. 289, 309–322 (2011)CrossRefGoogle Scholar
  24. 24.
    Sastry, N.V., Vaghela, N.M., Aswal, V.K.: Effect of alkyl chain length and head group on surface active and aggregation behavior of ionic liquids in water. Fluid Phase Equilib. 327, 22–29 (2012)CrossRefGoogle Scholar
  25. 25.
    Jeon, Y., Sung, J., Kim, D., Seo, C., Cheong, H., Ouchi, Y., Ozawa, R., Hamaguchi, H.: Structural change of 1-butyl-3-methylimidazolium tetrafluoroborate+water mixtures studied by infrared vibrational spectroscopy. J. Phys. Chem. B 112, 923–928 (2008)CrossRefGoogle Scholar
  26. 26.
    Takamuku, T., Kyoshoin, Y., Shimomura, T., Kittaka, S., Yamaguchi, T.: Effect of water on structure of hydrophilic imidazolium-based ionic liquid. J. Phys. Chem. B 113, 10817–10824 (2009)CrossRefGoogle Scholar
  27. 27.
    Takamuku, T., Shimomura, T., Sadacane, K., Seto, H.: Aggregation of 1-dodecyl-3-methylimidazolium nitrate in water and benzene studied by SANS and 1H NMR. Phys. Chem. Chem. Phys. 14, 11070–11080 (2012)CrossRefGoogle Scholar
  28. 28.
    Katayanagi, H., Nishikawa, K., Shimozaki, H., Miki, K., Westh, P., Koga, Y.: Mixing schemes in ionic liquid–H2O systems: a thermodynamic study. J. Phys. Chem. B 108, 19451–19457 (2004)CrossRefGoogle Scholar
  29. 29.
    Bowers, J., Butts, C.P., Martin, P.J., Vergara-Gutierrez, M.C.: Aggregation behavior of aqueous solutions of ionic liquids. Langmuir 20, 2191–2198 (2004)CrossRefGoogle Scholar
  30. 30.
    Almasy, L., Turmine, M., Perera, A.: Structure of aqueous solutions of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate by small-angle neutron scattering. J. Phys. Chem. B 112, 2382–2387 (2008)CrossRefGoogle Scholar
  31. 31.
    Nishikawa, K., Hayashi, H., Iijima, T.: Temperature dependence of the concentration fluctuation, the Kirkwood–Buff parameters, and the correlation length of tert-butyl alcohol and water mixtures studied by small-angle X-ray scattering. J. Phys. Chem. 93, 6559–6565 (1989)CrossRefGoogle Scholar
  32. 32.
    Wakisaka, A., Komatsu, S., Usui, Y.: Solute–solvent and solvent–solvent interactions evaluated through clusters isolated from solutions: preferential solvation in water–alcohol mixtures. J. Mol. Liquids 90, 175–184 (2001)CrossRefGoogle Scholar
  33. 33.
    Takamuku, T., Tabata, M., Yamaguchi, A., Nishimoto, J., Kumamoto, M., Wakita, H., Yamaguchi, T.: Liquid structure of acetonitrile–water mixtures by x-ray diffraction and infrared spectroscopy. J. Phys. Chem. B 102, 8880–8888 (1998)CrossRefGoogle Scholar
  34. 34.
    Takamuku, T., Honda, Y., Fujii, K., Kittaka, H.: Aggregation of imidazolium ionic liquids in molecular liquids studied by small-angle neutron scattering and NMR. Anal. Sci. 24, 1285–1290 (2008)CrossRefGoogle Scholar
  35. 35.
    Shimomura, T., Fujii, K., Takamuku, T.: Effects of alkyl-chain length on mixing state of imidazolium-based ionic liquid–methanol solutions. Phys. Chem. Chem. Phys. 12, 12316–12324 (2010)CrossRefGoogle Scholar
  36. 36.
    Smirnova, N.A., Vanin, A.A., Safonova, E.A., Pukinsky, I.B., Anufrikov, Y.A., Makarov, A.L.: Self-assembly in aqueous solutions of imidazolium ionic liquids and their mixtures with an anionic surfactant. J. Colloid Interface Sci. 336, 793–802 (2009)CrossRefGoogle Scholar
  37. 37.
    Smirnova, N.A., Safonova, E.A.: Ionic liquids as surfactants. Russ. J. Phys. Chem. A 84, 1695–1704 (2010)CrossRefGoogle Scholar
  38. 38.
    Smirnova, N.A., Safonova, E.A.: Micellization in solutions of ionic liquids. Colloid J. 74, 254–265 (2012)CrossRefGoogle Scholar
  39. 39.
    Goodchild, I., Collier, L., Millar, S.L., Prokes, I., Lord, J.C.D., Butts, C.P., Bowers, J., Webster, J.R.P., Heenan, R.K.: Structural studies of the phase, aggregation and surface behavior of 1-alkyl-3-methylimidazolium halide+water mixtures. J. Colloid Interface Sci. 307, 455–468 (2007)CrossRefGoogle Scholar
  40. 40.
    Nockemann, P., Binnemans, K., Driesen, K.: Purification of imidazolium ionic liquids for spectroscopic applications. Chem. Phys. Lett. 415, 131–136 (2005)CrossRefGoogle Scholar
  41. 41.
    Iwase, H., Endo, H., Katagiri, M., Shibayama, M.: Modernization of the small-angle neutron scattering spectrometer SANS-U by upgrade to a focusing SANS spectrometer. J. Appl. Cryst. 44, 558–568 (2011)CrossRefGoogle Scholar
  42. 42.
    Shibayama, M., Matsunaga, T., Nagao, M.: Evaluation of incoherent scattering intensity by transmission and sample thickness. J. Appl. Crystallogr. 42, 621–628 (2009)CrossRefGoogle Scholar
  43. 43.
    Hayter, J.B., Penfold, J.: An analytic structure factor for macroion solutions. Mol. Phys. 42, 109–118 (1981)CrossRefGoogle Scholar
  44. 44.
    Guinier, A., Fournet, G.: Small-Angle Scattering of X-rays. Wiley, New York (1955)Google Scholar
  45. 45.
    Helgeson, M.E., Hodgdon, T.K., Kaler, E.W., Wagner, N.J.: A systematic study of equilibrium structure, thermodynamics, and rheology of aqueous CTAB/NaNO3 wormlike micelles. J. Colloid Interface Sci. 349, 1–12 (2010)CrossRefGoogle Scholar
  46. 46.
    Guo, L., Colby, R.H., Lin, M.Y., Dado, G.P.: Micellar structure change in aqueous mixtures of nonionic surfactants. J. Rheol. 45, 1223–1243 (2001)CrossRefGoogle Scholar
  47. 47.
    Guinier, A.: Diffraction of X-rays of very small angles: application of ultramicroscopic phenomenon. Ann. Phys. 12, 161–237 (1939)Google Scholar
  48. 48.
    Hirata, H., Hattori, N., Ishida, M., Okabayashi, H., Frusaka, M., Zana, R.: Small-angle neutron-scattering study of bis(quaternary ammonium bromide) surfactant micelles in water. Effect of the spacer chain length on micellar structure. J. Phys. Chem. 99, 17778–17784 (1995)CrossRefGoogle Scholar
  49. 49.
    Wang, J., Wang, H., Zhang, S., Zhang, H., Zhao, Y.: Conductivities, volumes, fluorescence, and aggregation behavior of ionic liquids [C4mim][BF4] and [Cnmim]Br (n = 4, 6, 8, 10, 12) in aqueous solutions. J. Phys. Chem. B 111, 6181–6188 (2007)CrossRefGoogle Scholar
  50. 50.
    Inoue, T., Ebina, H., Dong, B., Zheng, L.: Electrical conductivity study on micelle formation of long-chain imidazolium ionic liquids in aqueous solution. J. Colloid Interface Sci. 314, 236–241 (2007)CrossRefGoogle Scholar
  51. 51.
    In, M., Bendjeriou, B., Noirez, L., Grillo, I.: Growth and branching of charged wormlike micelles as revealed by dilution laws. Langmuir 26, 10411–10414 (2010)CrossRefGoogle Scholar
  52. 52.
    Kusano, T., Iwase, H., Yoshimura, T., Shibayama, M.: Structural and rheological studies on growth of salt-free wormlike micelles formed by star-type trimeric surfactants. Langmuir 28, 16798–16806 (2012)CrossRefGoogle Scholar
  53. 53.
    Seki, S., Kobayashi, T., Takei, K., Miyashiro, H., Hayamizu, K., Tsuzuki, S., Mitsugi, T., Umebayashi, Y.: Effects of cation and anion on physical properties of room-temperature ionic liquids. J. Mol. Liq. 152, 9–13 (2010)CrossRefGoogle Scholar
  54. 54.
    Shannon, R.D.: Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst. A 32, 751–767 (1976)CrossRefGoogle Scholar
  55. 55.
    Tanford, C.: The Hydrophobic Effect. Wiley, New York (1980)Google Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Institute for Solid State PhysicsThe University of TokyoKashiwaJapan
  2. 2.Department of Chemistry, Faculty of Science and EngineeringSaga UniversitySagaJapan

Personalised recommendations