ORIENTATIONAL ELASTIC DEFORMATIONS IN POLYMER LIQUID-CRYSTALS INDUCED BY ELECTRIC-FIELDS - AROMATIC POLYESTERS

Elastic deformations induced by electric fields were investigated in nematic layers of two thermotropically mesogenic aromatic polyesters, with different structures of flexible spacers, and of their two low molecular weight analogues. It was shown by means of the polarizing microscopy that, in a planar-concave homeotropic layer of a nematic with negative dielectric anisotropy, bend deformation in the direction of an electric field and splay deformations in directions normal to it are induced by this field. The threshold electrical potentials of structural transitions and the values of dielectric anisotropy of these nematics were determined. For a polymer nematic with a diethylene glycol spacer, a dispersion and sign inversion of dielectric anisotropy was found in the range of radio frequencies. This phenomenon may be explained by the relaxation of the longitudinal components of the dipole moments of the mesogenic units of polymer chains.