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Hierarchical Structure and Dynamics of an Ionic Liquid 1-Octyl-3-methylimidazolium Chloride



Osamu Yamamuro, Takeshi Yamada, Maiko Kofu, Masamichi Nakakoshi, Michihiro Nagao


We have performed the heat capacity, neutron diffraction, and neutron quasielas- tic scattering measurements of an ionic liquid 1-octyl-3-methylimidazolium chloride (C8mimCl). The heat capacity data revealed that C8mimCl exhibits a glass tran- sition with a large heat capacity jump at Tg = 214 K, which is lower than Tg of C4mimCl with a shorter alkyl-chain. In the neutron diffraction measurement for a deuterated analogue d-C8mimCl, the peaks associated with the inter-domain, inter- ionic and inter-alkyl-chain correlations appeared at (3, 11, and 14) nm-1, respec- tively. The temperature dependence of these peaks indicates that the packing of the alkyl-chains becomes more compact and the domains become more vivid and larger as decreasing temperature. The quasielastic neutron scattering measurements using neutron spin echo and time-of-flight type instruments demonstrated that C8mimCl has faster relaxations owing to the alkyl-group and a slower relaxation owing to the ions. The latter relaxation, which is related to the glass transition, is of non- exponential as in the α relaxation of glass-forming molecular liquids. The relaxation of domains could not be observed in the present experiment but should have re- laxation times longer than 100 ns. This is the first report to clarify temperature dependence of the hierarchical structure and relaxations simultaneously for a typical ionic liquid.
Journal of Chemical Physics


ionic liquid, dynamics, neutron spin echo, domain


Yamamuro, O. , Yamada, T. , Kofu, M. , Nakakoshi, M. and Nagao, M. (2011), Hierarchical Structure and Dynamics of an Ionic Liquid 1-Octyl-3-methylimidazolium Chloride, Journal of Chemical Physics, [online], (Accessed February 25, 2024)
Created August 2, 2011, Updated October 12, 2021