Physicochemical study of diethylmethylammonium methanesulfonate under anhydrous conditions

Hailong Pan; Pieter Geysens; Tristan Putzeys; Alessia Gennaro; Yingting Yi; Hua Li; Rob Atkin; Koen Binnemans; Jiangshui Luo; Michael Wübbenhorst

doi:10.1063/5.0011756

Physicochemical study of diethylmethylammonium methanesulfonate under anhydrous conditions

J Chem Phys. 2020 Jun 21;152(23):234504. doi: 10.1063/5.0011756.

Authors

Affiliations

¹ Laboratory for Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Leuven 3001, Belgium.
² Department of Chemistry, KU Leuven, 3001 Leuven, Belgium.
³ School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia.

PMID: 32571054
DOI: 10.1063/5.0011756

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 (σ_dc) above the melting/freezing point obeys the 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 σ_dc 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 content 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.