Photo-Regulation on Chiral Liquid Crystal by Intrinsic Chiral Diarylethene

Cholesteric phase liquid crystals, which are usually formed by introducing chiral molecules into achiral nematic phase liquid crystals, have attracted much attention because of their excellent external stimulus responsivity, selective reflection, and dynamic modulation properties. However, rare photoswitches show high bistability, large helical twisting power, and intrinsic chirality. Therefore, this paper introduces an intrinsic chiral diarylethene photoswitch with excellent thermal stability to construct a liquid crystal modulation system. Based on sterically-hindered diarylethene, we synthesize an intrinsic chiral photoswitch ap-BPA with benzaldehyde groups to increase the steric hindrance effect, which in turn increases the helical twisting power. The basic optical properties of the photoswitch are systematically tested, and the results show that the photoswitch possesses excellent photoresponsive properties, fatigue resistance and thermal stability. Furthermore, intrinsic chiral photoswitch is mixed with nematic liquid crystals to successfully construct a dynamically tunable liquid crystal system, and it is shown that the photoswitch exhibits a large helical twisting power (HTP) value of 155.43 µm⁻¹, with a variation of 94.72 μm⁻¹. This represnts a significant performance improvement compared to BBTE. What’s more, the tuning wavelength ranges of the liquid crystal systems of the molecule can span from the visible region to the near-infrared region, with a width of up to 530 nm. Finally, by performing optical writing patterns on the ap-BPA liquid crystal system, applications in daily anti-counterfeiting and optical diffraction are achieved.