Chiral, Thermally Irreversible and Quasi-Stealth Photochromic Dopant to Control Selective Reflection Wavelength of Cholesteric Liquid Crystal.

A chiral and thermally irreversible photochromic fulgide derivative incorporating an (R)-binaphthol unit in its acid anhydride moiety was used for the photoswitching of the pitch length of cholesteric liquid crystals. Since the absorption maximum wavelengths of both thermally stable photoisomers are nearly in the UV region (quasi-stealth photochromism), it can be exposed to visible light without inducing photochromic reactions. Therefore, when the photoswitching molecule is added to a permanent cholesteric liquid crystal whose reflection light wavelength is in the visible region, the UV light-induced photochromic reaction of the photoswitching molecule changes the wavelength of the reflection light in the visible light region. We have succeeded in regulating the color of cholesteric liquid crystalline cells between red and blue upon UV light irradiation. Attempts to introduce this system in polymer dispersed cholesteric liquid crystals are also described.

Chiral, Thermally Irreversible and Quasi-Stealth Photochromic Dopant to Control Selective Reflection Wavelength of Cholesteric Liquid Crystal.

The front cover artwork is provided by the group of Prof. Emeritus Yasushi Yokoyama and Prof. Takashi Ubukata. The image shows the generation of a colored image, whose origin is the UV-controlled selective reflection of visible light from a cholesteric liquid crystal containing chiral photochromic molecules. Read the full text of the Article at 10.1002/cphc.202000309.