Fluorescence Emission of Guest Molecules as a Tool of Surface Alignment Study in Nematic Liquid Crystals

A simple fluorescence method for surface alignment studies of nematic liquid crystals is presented. It is shown that, knowing the polarized fluorescence of a guest pleochroic dye, the surface order parameter can be calculated. For nematic liquid crystal matrixes with positive dielectric anisotropy and a pleochroic dye it is found that there is a remarkable difference between the degree of order at the surface and in the bulk, and that even in the isotropic temperature region the order parameter at the surface is not destroyed completely.