ANISOTROPIC DISPERSION FORCE EFFECTS FOR ALIGNMENT OF LIQUID-CRYSTALS ON RUBBED POLYSTYRENE SURFACES

We have studied the anisotropic dispersion force effects for alignment of liquid crystals (LCs) on rubbed polystyrene (PS) surfaces. We previously demonstrated that the nematic (N) LCs are shown to align in the direction per pendicular to the rubbing and polar anchoring strength is very weak compared to rubbed polyimide (PI) surfaces [D.-S. Seo et al.: Jpn. J. Appl. Phys. 31 (1992) 2165]. In microphotographs of the textures, we obtained the NLCs are shown to align in both direction parallel and perpendicular to the rubbing for region up to medium rubbing, however to align in the direction perpendicular to the rubbing for strong rubbing region. We suggest that the anisotropic dispersion force is very important rather than macro-surface groove effect to uniform alignment of LCs. We also observed the surface ordering of the NLCs on rubbed PS surfaces for strong rubbing is disordered. We suggest that the low polarization of the orientation surfaces is attributed to weak anchoring strength.