Hidden photoalignment of liquid crystals in the isotropic phase - art. no.021701

We found the effect of a hidden photoalignment of a dye-doped nematic liqui d crystal (LC) on a nonphotosensitive polymer surface after polarized irrad iation of the cell in the isotropic phase. We observed that irradiation res ulted in a uniform planar orientation of the LC after cooling to the mesoph ase. The direction of a light-induced easy axis on the polymer can he eithe r parallel or perpendicular to the polarization of the incident light, depe nding on the light intensity. We attribute this behavior to two mechanisms of photoalignment: light-induced adsorption of dye molecules on the substra te, and anisotropic desorption in a previously adsorbed dye layer. The expe rimental results on photoalignment of a LC on a thin dye film confirm our m odel.