Effects of high polymer concentration for alignment of liquid crystal on rubbed polyimide surfaces containing trifluoromethyl moieties

The effects of high polymer concentration for alignment of liquid crystal (LC) on rubbed polyimide (Pi) surfaces containing trifluoromethyl moieties have been successfully evaluated by measuring the pretilt angle, surface ordering, and polar anchoring strength. The pretilt angle of 5CB is increased by combination of steric interaction between the LCs and the substrate surfaces on rubbed special PI and low surface energy due to rich fluorine atoms on surfaces was demonstrated. The surface order parameter of 5CB for high polymer concentration is small compared to low polymer concentration. We suggest that the surface order parameter is decreased by low surface energy caused by rich fluorine atoms. The polar anchoring strength of 5CB near the clearing temperature for high polymer concentration is very weak compared to low polymer concentration. Finally, we suggest that the pretilt angle, surface ordering, and polar anchoring strength in 5CB strongly depend on character of polymer on surfaces.