Temperature Dependence of the Primary Relaxation in 1-Hexyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide

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• 作者：Olga Russina ; Mario Beiner ; Catherine Pappas ; Margarita Russina ; Valeria Arrighi ; Tobias Unruh ; Claire L. Mullan ; Christopher Hardacre ; Alessandro Triolo
• 刊名：Journal of Physical Chemistry B
• 出版年：2009
• 出版时间：June 25, 2009
• 年：2009
• 卷：113
• 期：25
• 页码：8469-8474
• 全文大小：236K
• 年卷期：v.113,no.25(June 25, 2009)
• ISSN：1520-5207

文摘

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 Å⁻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.