A Photoisomerizable Chiral Dopant for Fast and Precise Controlling the Reflection Band of the CLCN Film

Colorful cholesteric liquid crystal polymer network (CLCN) patterns have been applied for decoration and anti-counterfeiting. Generally, the handedness of the reflected lights is the same. In this paper, a chiral dopant derived from cyanostilbene is synthesized. Due to the isomerization and [2 + 2] photocycloaddition under the irradiation of the 365-nm UV light, it exhibits a great change in the helical twisting power. The cholesteric liquid crystal mixture prepared using this chiral dopant can be applied for rapid optical recording. Colorful CLCN patterns are also prepared, which can reflect both left- and right-handed circularly polarized lights. Namely, different patterns are observed through left- and right-handed circular polarizers. Due to the luminescent property of the chiral dopant and its isomers, circularly polarized luminescence is emitted from the CLCN films.