FIELD-INDUCED REORIENTATION OF NEMATIC LIQUID-CRYSTALS WITH TWOFOLD DEGENERATE ALIGNMENT ON SIOX SURFACES

We show that an electric field normal to the boundaries confining a sl ab of nematic liquid crystals can induce a large change of the in-plan e preferred orientation (i.e., the azimuthal angle). The degree of reo rientation is controlled by the surfaces which have been coated with o bliquely evaporated SiOx. The experimental data are compared with simu lations of a theoretical model where the effects of both large and sma ll electric fields on the nematic orientation are considered. The reor ientation phenomenon caused by the electric field appears to be a thre shold phenomenon, due to the symmetry of the initial nematic orientati on. For fields larger than the critical one, it is possible to define an effective surface energy for the system, containing the anisotropic surface energy and the contribution from the electric field. [S1063-6 51X(98)12211-0].