Light-controllable hybrid aligning layer based on LIPSS on sapphire surface and PVCN-F film

• Published in: Journal of molecular liquids 2023-10, Vol.387, p.122623, Article 122623
• Main Authors: Gvozdovskyy, I., Bratova, D., Kazantseva, Z., Malyuta, S., Lytvyn, P., Schwarz, S., Hellmann, R.
• Format: Article
• Language: English
• Subjects: Aligning layer; Atomic force microscopy; Azimuthal anchoring energy; Contact angle; LIPSS; Nematic liquid crystal; Photoalignment; PVCN-F
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2023.122623

[Display omitted] •Structured sapphire surfaces coated with photosensitive polymer as hybrid aligning layers were studied.•Structured sapphire surfaces, possessing different width of unstructured gap, were fabricated by using LIPSS.•Azimuthal anchoring energy of hybrid aligning layer depends on width of unstructured gap and irradiation time.•The dramatic increase in azimuthal anchoring energy value under UV light treatment of hybrid aligning layer was found.•The near zero azimuthal anchoring energy value for the hybrid aligning layer was also found. The creation of aligning layers for the uniform orientation of liquid crystals is significant for both research and the application of liquid crystals. For all applications, the creation of aligning layers possessing controllable characteristics such as azimuthal and polar anchoring energies, easy-axis of director alignment and pretilt angle, in the same way as it is achieved by using photoaligning layers processed by light, is very important. Here, aligning properties of hybrid aligning layers created on the basis of sapphire surfaces additionally coated by photoaligning layer of PVCN-F are studied. These hybrid layers possess the properties of the nano-structured sapphire layer and the photosensitive PVCN-F layer, and complement each other. The irradiation time dependence of the azimuthal anchoring energy of the hybrid layers is studied. By using certain experimental conditions during irradiation of hybrid layers, e.g., polarization of light and irradiation time, a minimum value of the azimuthal anchoring energy, close to zero, was obtained. Atomic force microscope studies of the irradiated hybrid layers were also carried out. It was found that the behavior of the contact angle of nematic droplets placed on treated sapphire surfaces are in good agreement with properties of hybrid aligning layers and parameters of structuring surface obtained from AFM images.