ELECTROHYDRODYNAMIC CONVECTION UNDER A NEMATIC-ISOTROPIC INTERFACE

We report experimental results on electrohydrodynamic convection of ne matic liquid crystals having a free surface at the nematic-isotropic i nterface. The applied electric field is orthogonal to the free surface . In this configuration, the thickness of the nematic layer is linearl y proportional to the reduced temperature. We observe that the thresho ld voltage for convective rolls varies significantly as the thickness is decreased, while the dimensionless wave vector remains constant. Wh en convection occurs, the nematic-isotropic interface undergoes a peri odic distortion, and we argue that this distortion is largely responsi ble for the relatively large variation of threshold voltage with layer thickness.