Physicochemical Properties of Binary Ionic Liquid–Aprotic
Solvent Electrolyte Mixtures
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Abstract
The properties of mixtures of ionic liquids (ILs) with
a variety
of different aprotic solvents have been examined in detail. The ILs
selectedbis(trifluoromethanesulfonyl)imide (TFSI<sup>–</sup>) salts with <i>N</i>-methyl-<i>N</i>-pentylpyrrolidinium
(PY<sub>15</sub><sup>+</sup>), -piperidinium (PI<sub>15</sub><sup>+</sup>), or -morpholinium (MO<sub>15</sub><sup>+</sup>) cationsenabled
the investigation of how cation structure influences the mixture properties.
This study includes the characterization of the thermal phase behavior
of the mixtures and volatility of the solvents, density and excess
molar volume, and transport properties (viscosity and conductivity).
The mixtures with ethylene carbonate form a simple eutectic, whereas
those with ethyl butyrate appear to form a new IL–solvent crystalline
phase. Significant differences in the viscosity of the mixtures are
found for different solvents, especially for the IL-rich concentrations.
In contrast, only minor differences are noted for the conductivity
with different solvents for the IL-rich concentrations. For the solvent-rich
concentrations, however, substantial differences are noted in the
conductivity, especially for the mixtures with acetonitrile