Effect of photoaligning azo dye structure on liquid crystal anchoring energy

Abstract

A method of controlling anchoring energy of surface interaction of liquid crystal photoaligning substances is considered to enhance the liquid crystal display performances. An important parameter of the dye's molecular structure that determines the ratio of polar and azimuthal anchoring energy is the ability to form dimers. The values of dimerization thermodynamic potentials have been found. The probability of the formation of dye molecules dimers is evaluated. The bonds conjugation transfer via intermolecular hydrogen bond is revealed, and anisotropy of polarizability of the hydrogen bond is evaluated. The effect of dimerization on polar and azimuthal anchoring energy of liquid crystalazo dye systemis shown.

Relation between dichroism of photoalignment azo dyes and their orientation under light wave field

“…The values of determined from relation are given in Table . In previous papers, it was proposed that the values of both azimuthal and polar anchoring energies could be explained by the fact that the dye molecules form flat dimers. Further, for the sake of simplicity, we consider the interaction only of the CD‐1 dimer with the electric field, because the molecules of many dyes used in photoorientation (SD‐1, ATA‐2, etc.)…”

“…Azo dyes are most frequently used materials for this application. The common mechanism of photoorientation involves the radiation absorption and succeeding relaxation of dye molecules . The radiation absorption is followed by the torque acting on dyes due to the optical anisotropy (linear dichroism), according to general Le Chatelier–Braun principle.…”

“…The common mechanism of photoorientation involves the radiation absorption and succeeding relaxation of dye molecules. [20][21][22][23][24] The radiation absorption is followed by the torque acting on dyes due to the optical anisotropy (linear dichroism), according to general Le Chatelier-Braun principle. This torque tends to orient the dye molecules in the direction of minimum radiation energy dissipation in accordance with general variational principle by Onsager.…”

“…12,13 Problem of intensive light influence on the dyes' dimers as well as the single molecule performances in the photoalignment process is of special interest for both optics and display technology because of correlation of the azo dye dimer structure with both polar and azimuthal anchoring energy values. 11,23,24 The present work is devoted to the study of the orientation of the dye molecules under action of the intensive light (laser) radiation.…”