Abstract
Binary mixtures of the aprotic protophobic solvent nitromethane (NM) and the protic room-temperature ionic liquid ethylammonium nitrate (EAN) were studied with dielectric relaxation spectroscopy in the two single-phase regions, 0 < chi(EAN) <= 0.013 and 0.4 <= chi(EAN) < 1, of the binary mixtures at 25 degrees C. All spectra were well described by a superposition of two relaxation processes whose ...
Abstract
Binary mixtures of the aprotic protophobic solvent nitromethane (NM) and the protic room-temperature ionic liquid ethylammonium nitrate (EAN) were studied with dielectric relaxation spectroscopy in the two single-phase regions, 0 < chi(EAN) <= 0.013 and 0.4 <= chi(EAN) < 1, of the binary mixtures at 25 degrees C. All spectra were well described by a superposition of two relaxation processes whose origins were of composite nature. At low chi(EAN) the solutions behave as a strongly associated electrolyte, displaying moderate ion solvation by nitromethane at the infinite-dilution limit. At high chi(EAN) far from the miscibility gap, the observed dynamics represents the typically observed behaviour of a lubricated ionic liquid smoothly reaching the properties of pure EAN. Additionally, neat NM was investigated in the temperature range of 5 to 65 degrees C to explore its potential as a calibration standard in dielectric spectroscopy. The obtained 0.05 to 89 GHz spectra were well fitted by a single Debye equation. The dynamics of this medium-permittivity dipolar liquid is governed by rotational diffusion of NM dipoles close to slip boundary conditions with only weak dipole-dipole correlations. Unfortunately, difficulties in obtaining samples of reproducible purity discredit NM as a calibration standard for dielectric measurements. (C) 2016 Elsevier B.V. All rights reserved.
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