Influence of smectic liquid crystals on the Poisson-Boltzmann distribution of ions near charged surfaces

Abstract

We have developed a model for the distribution of ions in a sample of smectic-A liquid crystal taken between two charged plates, by including an appropriate one-dimensionally periodic potential. In samples which are in contact with an external reservoir, there is an influx of ions to the cell attracted by the minima in the periodic potential, effectively reducing the screening length compared to the Debye length in the nematic phase. The smectic potential has maxima near the plates, which leads to an inward longitudinal pressure unlike in nematic. In the case of sealed cells without any contact with an external reservoir, the ion distribution in the smectic follows closely that in the nematic, except for the oscillations arising from the smectic potential.