Transport Properties of Short Alkyl Chain Length Dicationic Ionic Liquids—The Effects of Alkyl Chain Length and Temperature

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• 作者：Majid Moosavi ; Fatemeh Khashei ; Ali Sharifi ; Mojtaba Mirzaei
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2016
• 出版时间：August 24, 2016
• 年：2016
• 卷：55
• 期：33
• 页码：9087-9099
• 全文大小：914K
• 年卷期：0
• ISSN：1520-5045

文摘

Some transport properties of imidazolium-based short alkyl chain length dicationic ionic liquids (DILs) ([C_n(mim)₂][NTf₂]₂), including shear viscosity, diffusion coefficient, and electrical conductivity, have been measured and analyzed as a function of temperature and alkyl chain length. Also, the dependence of viscosity on shear rate has been investigated. The small intercepts of plots of shear stress versus shear rate and also the small variations of the viscosity values with changing shear rate show that the studied DILs are moderately non-Newtonian fluids. Temperature dependence of the viscosity of these ILs shows non-Arrhenius behavior which can be fitted well using four well-known equations, namely, power law, Litovitz, Vogel–Fulcher–Tammann (VFT), and Ghatee et al. equations. The activation thermodynamic parameters of these DILs were calculated. The positive values of Gibbs free energy of activation show that the slip of two layers of the fluid is a nonspontaneous process. DOSY NMR spectroscopy was used to measure the diffusion coefficients of the ionic species in these DIL systems. Also, the other parameters such as hydrodynamic radii and transport numbers of anions and cations and dissociation and association degrees of IL molecules were calculated from the diffusion coefficient and viscosity data. We measured the electrical conductivity of these ILs at different temperatures. The ionicity of these DILs which was evaluated using the Walden plot diagnostic showed that these fluids are “subionic”. With the help of the m-fragility parameter, we measured the fragility of these fluids and indicated that these DILs are in the intermediate to fragile range. Also, we showed a correlation between the m-fragility and the ionicity of these ILs.