Temperature dependence of the primary relaxation in 1-hexyl-3- methylimidazolium bis{(trifluoromethyl)sulfonyl}imide

Olga Russina, Mario Beiner, Catherine Pappas, Margarita Russina, Valeria Arrighi, Tobias Unruh, Claire L. Mullan, Christopher Hardacre, Alessandro Triolo

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We present results from complementary characterizations of the primary relaxation rate of a room temperature ionic liquid (RTIL), 1-hexyl-3- methylimidazolium bis{(trifluoromethyl)sulfonyl} imide, [C6mim] [Tf2N], over a wide temperature range. This extensive data set is successfully merged with existing literature data for conductivity, viscosity, and NMR diffusion coefficients thus providing, for the case of RTILs, a unique description of the primary process relaxation map over more than 12 decades in relaxation rate and between 185 and 430 K. This unique data set allows a detailed characterization of the VTF parameters for the primary process, that are: B = 890 K, T0 = 155.2 K, leading to a fragility index m = 71, corresponding to an intermediate fragility. For the first time neutron spin echo data from a fully deuteriated sample of RTIL at the two main interference peaks, Q = 0.76 and 1.4 A°-1 are presented. At high temperature (T > 250 K), the collective structural relaxation rate follows the viscosity behavior; however at lower temperatures it deviates from the viscosity behavior, indicating the existence of a faster process. © 2009 American Chemical Society.

Original languageEnglish
Pages (from-to)8469-8474
Number of pages6
JournalJournal of Physical Chemistry B
Issue number25
Publication statusPublished - 25 Jun 2009


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