Influence of flexoelectricity on electrohydrodynamic instabilities in nematics

Restricted Access. Proceedings of the 12th international liquid crystals conference held in 1988 at Freiburg, 1989We have incorporated the flexoelectric terms in developing one-dimensional models of E.H.D. instabilities in nematics both under D.C. and A.C. excitations. It is shown that, using this model, we can account for the following experimental observations, which could not be adequately explained by earlier models: (i) The observation of oblique rolls whose wave vector q makes an angle agr with the undistorted director n0, up to some frequency v0 in the conduction regime; (ii) the oblique rolls found in the dielectric regime; and (iii) the 'longitudinal' E.H.D. instabilities in some systems with negative conductivity anisotropy. We also present some experimental observations under D.C. excitation