Diffusion mechanisms in smectic ionic liquid crystals: Insights from coarse-grained MD simulations

We present the results of MD simulations, using a coarse grained force field, concerning the mechanism of diffusion in ionic liquid crystals. The dynamical properties of the recently characterized (G. Saielli, Soft Matter, 2012, 8, 10279) model system of 1-hexadecyl-3-methylimidazolium nitrate in the smectic A phase are analysed in detail. Comparison is made with the dynamical behaviour of thermotropic non-ionic smectic liquid crystals (LCs) and with that of lamellar phases of surfactant-water mixtures. The self-diffusion anisotropy, that is the ratio between the parallel and perpendicular diffusion coefficients, is consistent with that of non-ionic smectic LCs, though a significant contribution to the parallel diffusion is given by "pore" defects, similarly to what was observed in lamellar phases. © 2013 The Royal Society of Chemistry.