SURFACE POLARIZATION AND FLEXOELECTRIC EFFECT

In order to evaluate the order of magnitude and to establish the origin of the surface polarization, experimental investigations of direct piezoelectrical effect in nematic liquid crystals have been performed. The experimental setup used allows the temperature dependence of the electrical response of a nematic sample, substituted to periodic acoustic perturbation of one boundary, to be determined. The experimental data show that the contribution of the surface polarization to the electrical response of the nematic sample is usually negligible with respect to the flexoelectric polarization. An estimation of the flexoelectric coefficients of various liquid crystals is reported.