Photostationary RGB Selective Reflection from Self-Organized Helical Superstructures for Continuous Photopatterning

Light-driven cholesteric liquid crystals (CLCs) are intriguing materials due to the dynamic tuning of their selective reflection, which originates from self-organized helical superstructures, in response to light. However, CLC systems are restricted to displaying static optically addressed images and need to be initialized or refreshed before every new image can be displayed. Herein, a novel tuning mechanism based on a partial photochemical phase transition is proposed to enable continuous patterning of photostationary red, green, and blue (RGB) colors in a CLC system, which contains nonresponsive chiral dopants and o-fluoroazobenzenes (Fazo) to serve as the photoswitch. Distinct isomer ratios of Fazo result in precise light-directed RGB colors for the photostationary states, and, thus, a fixed relationship is established between the light stimulus and the reflection color. Accordingly, the RGB color patterns can be continuously erased and rewritten under light irradiation with different wavelengths. A photocontrollable "Tetris game" is demonstrated for the first time according to the programmable modulation of the CLC reflection, providing a new concept for optically rewritable displays.