ANOMALOUS MIXING STATE OF IONIC LIQUIDS BASED SOLUTIONS

H. Abe1, Y. Imai1 and Y. Yoshimura2


1Department of Materials Science and Engineering, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan
2Department of Applied Chemistry, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan

Proceedings of the 3rd International Congress on Green Process Engineering (2011) 50.

Abstract
Anomalous water behaviors are enhanced inside room temperature ionic liquid (RTIL). A variety of mixing states of RTIL-H2O mixtures were investigated using wide angle X-ray scattering (WAXS), small angle X-ray scattering (SAXS) and optical absorption in UV-vis region. The RTIL is N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate, [DEME][BF4]. By the systematic experiments, hierarchy structure in the mixtures appeared depending on water concentrations even at a liquid state. The specific water network developed over the medium-range in [DEME][BF4]-85~95 mol% H2O. All anomalies are probably induced by intrinsic hydrogen bonding of a water molecule.

Figure 1.
Phase diagrams of [DEME][BF4]-H2O mixtures


Figure 2.
A [DEME] cation and an [BF4] anion.
Figure 3.
Small angle scattering experiments.
Figure 4.
Simultaneous WAXS and DSC measurements.
Figure 5.
Density of [DEME][BF4]-H2O mixture.
Figure 6.
WAXS patterns at room temperature.
Figure 7.
H2O concentration dependences of Q position at the maximum intensity, Qmax of WAXS patterns (Fig. 5).
Figure 8.
H2O concentration dependence of intensity of prepeak position in WAXS. Q position is 2.1 (nm-1), which is provided by the allow in Fig. 5.
Figure 9.
SAXS intensities as a function of H2O concentrations.
Figure 10.
H2O concentration dependence of correlation length, ��, which is obtained by Ornstein Zernike
Figure 11.
Optical absorption spectra as a function of water concentration. The inset shows absorption spectrum of pure water.
Figure 12.
Water concentration dependence of the optical absorption coefficient at 4.7 eV.
Figure 13.
Hierarchy structure of [DEME][BF4]-H2O.
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