Vitaly V. Chaban, Iuliia V. Voroshylova, Oleg N. Kalugin, Oleg V. Prezhdo
We apply a new methodology in the force field generation (PCCP 2011, 13,
7910) to study the binary mixtures of five imidazolium-based room-temperature
ionic liquids (RTILs) with acetonitrile (ACN). The investigated RTILs are
composed of tetrafluoroborate (BF4) anion and dialkylimidazolium cations, where
one of the alkyl groups is methyl for all RTILs, and the other group is
different for each RTILs, being ethyl (EMIM), butyl (BMIM), hexyl (HMIM), octyl
(OMIM), and decyl (DMIM). Specific densities, radial distribution functions,
ionic cluster distributions, heats of vaporization, diffusion constants, shear
viscosities, ionic conductivities, and their correlations are discussed. Upon
addition of ACN, the ionic conductivity of RTILs is found to increase by more
than 50 times, that significantly exceeds an impact of most known solvents.
Remarkably, the sharpest conductivity growth is found for the long-tailed
imidazolium-based cations. This new fact motivates to revisit an application of
these binary systems as advanced electrolytes. The ionic conductivity
correlates generally with a composition of ionic clusters, simplifying its
predictability. In turn, the addition of ACN exponentially increases diffusion
and decreases viscosity of the imidazolium-based RTILs/ACN mixtures. Large
amounts of acetonitrile stabilize ion pairs, but ruin greater ionic clusters.
View original:
http://arxiv.org/abs/1202.1006
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