Liquid Crystal Orientation Induced by Van Der Waals Interaction

It has been discovered that liquid crystals alignment on an inorganic surface such as SiO2 can either be homogeneously or homeotropically depending on the dielectric anisotropy being positive or negative, respectively. Van der Waals interaction, or induced dipole-dipole interaction taking into account the anisotropy of LC polarizabilities is responsible for such orientation, when all the other type of interactions between liquid crystal and surfaces is absent. In addition, an extended order electricity model was used to qualitatively explain the experimental results on pretilt angles.