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Keywords:

Science & Technology, Physical Sciences, Chemistry, Physical, Physics, Atomic, Molecular & Chemical, Chemistry, Physics, BASE IONIC LIQUIDS, THERMOPHYSICAL PROPERTIES, LOCAL COORDINATION, THERMAL-STABILITY, AQUEOUS-SOLUTION, BINARY-MIXTURES, PROTON, ACID, WATER, TRANSPORT, 02 Physical Sciences, 03 Chemical Sciences, 09 Engineering, Chemical Physics, 34 Chemical sciences, 40 Engineering, 51 Physical sciences

Abstract:

The protic ionic liquid diethylmethylammonium methanesulfonate ([DEMA][OMs]) was analyzed in depth by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and broadband dielectric spectroscopy (BDS) under anhydrous conditions. Karl Fischer titration, NMR and FT-IR spectra confirmed the high purity of [DEMA][OMs]. The melting point (37.7 °C) and the freezing point (14.0 °C) obtained by DSC agree well with the values determined by BDS (40.0 °C and 14.0 °C). The dc conductivity (σdc) above the melting/freezing point obeys Vogel-Fulcher-Tammann (VFT) equation well and thus the proton conduction in [DEMA][OMs] is assumed to be dominated by the vehicle mechanism. In contrast, the σdc below the melting/freezing point can be fitted by the Arrhenius equation separately and therefore the proton conduction is most likely governed by the proton-hopping mechanism. The non-negligible influence of previously reported low water contents on the physicochemical properties of [DEMA][OMs] is found, indicating the importance of reducing water content as much as possible for the study of “intrinsic” properties of protic ionic liquids.