Advances in model-independent restoration of the liquid crystal surface anchoring potential

• Published in: Molecular Crystals and Liquid Crystals 2021-05, Vol.713 (1), p.1-14
• Main Authors: Belyakov, V. A., Shmeliova, D. V., Semenov, S. V., Kharlamov, S. S.
• Format: Article
• Language: English
• Subjects: Alignment; Axes (reference lines); Cholesteric liquid crystals; Crystal surfaces; Grandjean-Cano wedge; Irradiation; Nematic crystals; photo alignment; Polarization; polarization microscope technique; Radiation dosage; Restoration; surface anchoring potential restoration
• ISSN: 1542-1406; 1563-5287; 1527-1943
• DOI: 10.1080/15421406.2020.1856528

We extend further the theoretical and experimental studies of the actual surface anchoring potential restoration by polarization microscope technique in a wedge-shaped cell with weak surface anchoring forces filled by a chiral nematic liquid crystal (in Grandjean-Cano Wedge). To realize the theoretically predicted options of observation of large director deviation angles from the easy axes the experimental studies of director distribution in Grandjean-Cano zones were performed for differing easy axes orientations at the wedge surfaces. A weak surface anchoring at one wedge surface was obtained by a photo-alignment technique. A strong surface anchoring at the second wedge surface was also obtained by a photo-alignment technique with an enlarged irradiation dose. There were observed walls with weak jumps of the director orientation between first neighboring Grandjean-Cano zones. Some experimentally obtained polarization microscope images demonstrate partially unwound director structures in zero Grandjean-Cano zone. To ensure optimal parameters of the further experiments on the actual surface anchoring potential restoration theoretical calculations of the director distribution in individual Grandjean-Cano zones were performed for various model surface anchoring potentials. It was found that especially promising for description of the experimentally found director distribution is the D-potential. As a result of the present studies the angular range of a model-independent actual azimuthal surface anchoring potential restoration was enlarge (up to π/3) and the ways of an actual surface anchoring potential restoration in a whole angular range of its determination are discussed.