Photo‐optical liquid crystal cells driven by molecular rotors

Photochemical regulation of in‐plane alignment of a nematic liquid crystal is presented. A quartz plate surface was modified with 4‐hexyl‐4’‐hexyloxyazobenzene substituted with triethoxysilyl group through a spacer at the 2’ position to introduce the side‐on type azobenzene unit of the surface. A liquid crystal hybrid cell fabricated with the azo‐modified plate was irradiated with linearly polarized visible light for the n‐π* transition. This resulted in the in‐plane reorientation of the liquid crystal molecules to afford homogeneous alignment. Discussion is made on the mechanism of the in‐plane alignment regulation, and the concept of a molecular rotor is proposed.