Insights on cholinium- and piperazinium-based ionic liquids under external electric fields: A molecular dynamics study

The rotational and translational response of cholinium benzoate, cholinium salicylate, piperazinium benzoate, and piperazinium salicylate to static and dynamic external electric fields was studied using non-equilibrium molecular dynamics simulations. The existence of strong intrinsic electric fields in the studied fluids requires intensities larger than 0.25 V A degrees (1) to obtain remarkable changes in the fluids' properties, such as rotational motion, dipolar alignment, or ion diffusivities. Very effective dipolar alignment with the applied fields is obtained showing rotational motions in the direction of the applied field, increasing with field intensity and decreasing with field frequency. Translational movement is clearly improved by the applied fields specially for strong fields and low frequencies, which lead to ionic diffusivities increasing up to two orders of magnitude for the stronger fields in comparison with zero field situations, and thus, increasing remarkably fluids' electrical conductivity. The effect of external electric fields on the studied ionic liquids is weaker than in common imidazolium-based ionic liquids. (C) 2013 AIP Publishing LLC.