Surface Polarization and Flexoelectricity in Nematic Liquid Crystals

We propose a technique for the measurement of the surface electric polarization in nematic liquid crystals from the birefringence variations of the texture under weak vertical electric field. We study experimentally 5CB aligned on SiO layer with strong tilted anchoring. We show that in this system the surface polarization is one order of magnitude stronger than the bulk flexoelectric polarization of 5CB reported before. We discuss the sign and the magnitude of the surface polarization and the reliability of the proposed method.