LPUV-assisted vapor deposition polymerization of polyazomethine films for molecular alignment of liquid crystals in TN cell

Rubbing free alignment of Liquid crystals (LC) is crucial in display technology. In this research, the photoaligned polyazomethine thin films fabricated by UV-assisted Vapor Deposition Polymerization (VDP) method were used as alignment layers for nematic liquid crystal. The photoalignment of polyazomethine films was generated by irradiation of a linearly polarised UV light (LPUV) during film formation and reaction process, upon the same manner as azobenzene moieties, i.e. trans-cis-trans isomerisation cycles. A twist nematic liquid crystal cell assembled with uniaxial oriented polyazomethine films as the substrates exhibits a typical response and a uniform texture. In addition, the viscoelastic properties of liquid crystal on the uniaxial oriented polyazomethine were measured by the Quartz Crystal Microbalance (QCM) method. It was found that the anchoring was strong owing to the strong interaction between highly oriented polyazomethine and LC molecules. LPUV-assisted VDP method is a powerful strategy that contributes to the development of alignment layer of LC and beyond.