INVESTIGATION OF THE TEMPERATURE DEPENDENCE OF SURFACE ANCHORING ENERGY FOR LIQUID CRYSTALS

The surface anchoring of nematic liquid crystals is an important coefficient which expresses the effect of liquid crystal alignment and the mechanism of the surface alignment. The surface azimuthal anchoring energy can be obtained by measuring the twist angle in the twist cell and the surface torsional angle between the rubbing direction and the liquid crystal director at the substrate boundary. The temperature dependence of the surface anchoring energy at 5CB-polyimide (PI) interface was studied. The surface anchoring energy decreases with increase of the temperature from ５.０×１０ －5 Ｊ／ｍ 2 at 25.５℃ to ５.０×１０ －6 Ｊ／ｍ 2 at 35.0℃. Meanwhile, the extrapolation length ｄ e increases from 80nm at 25.5℃ to ３７０ｎｍ at ０.５℃ below Ｔ c . This result clearly signifies the important role of the ordered structure of the nematic interface in determining the temperature dependence of the anchoring strength at the ５ＣＢ-PI interface.