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Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P126
Dynamics of Ionic Liquids by means of QENS
Jan Peter Embs 1 , Fanni Juranyi 2 , Rolf Hempelmann 1
1 FR 8.1 Physikalische Chemie, Universität des Saarlandes, 66041 Saarbrücken –
2 Laboratory for Neutron Scattering, PSI and ETH Zürich, CH-5232 Villigen-PSI,
Switzerland
Ionic liquids (IL), i.e. ionic melts with melting points below 373 K, have attracted
considerable attention in recent years as solvents for a variety of applications including
electrodeposition, batteries, catalysis, separations and organic synthesis [1,2].
A quasielastic neutron scattering study has been performed by Triolo et al. [3] in collaboration
with F. Juranyi on [bmim][PF6]. Recently, we have performed an experiment
on [N-butyl-N-methyl-pyrrolidinium] bis-(trifluoromethylsulfonyl) imide ([BMPyrr] Tf2N).
The typical spectra can be described as a superposition of an elastic component, a comparatively
narrow and a very broad Lorentzian. The Q-dependence of their line widths
and of the elastic incoherent structure factor (EISF), i.e. the ratio elastic intensity /
total intensity indicate localized side chain motion, see Fig. 1.
Investigations on fully protonated [N-alkyl-N-methyl-pyrrolidinium] Tf2N (here, alkyl
means ethyl, butyl, octyl, etc.) samples using our cold neutron time-of-flight spectrometer
FOCUS are in progress now.
[1] M.J. Earle and K.R. Seddon, Pure Appl. Chem. 72 (2000) 1391
[2] T. Welton, Chem. Rev. 99 (1999) 2071
[3] A. Triolo, O. Russina, V. Arrighi, F. Juranyi, S. Janssen and M.C. Gordon, J.
Chem. Phys. 119 (2003) 8549
Fig. 1: Left : widths
(FWHM) of the three components,
right : EISF both as
function of Q.