EFFECT OF SURFACE ELECTRIC-FIELD ON THE ANCHORING OF NEMATIC LIQUID-CRYSTALS

We analyse the influence of adsorbed ions and the resulting surface el ectric field and its gradient on the anchoring properties of nematics with ionic conductivity. We take into account two physical mechanisms for the coupling of the nematic director with the surface electric fie ld: (i) the dielectric anisotropy and (ii) the coupling of the quadrup olar component of the flexoelectric coefficient with the field gradien t. It is shown that for sufficiently large fields near saturated cover age of the adsorbed ions; there can be a spontaneous curvature distort ion in the cell even when the anchoring energy is infinitely strong. W e also discuss the director distortion when the anchoring energy of th e surface is finite.