Asymmetric ionic adsorption and cell polarization in liquid crystals

A model to determine the steady-state distribution of ionic charges in a liquid sample, in the shape of a slab, whose limiting surfaces are supposed to adsorb positive ions with different adsorption energies, is proposed. It is used to explain the asymmetric electro-optical response in a liquid-crystal cell recently observed. The ionic adsorption gives rise to a difference of potential between the surfaces which can be responsible for the existence of an internal field. It changes the effective voltage thresholds for the reorientation of the liquid crystal when external fields are applied.