Azopyrazole‐Based Axially Chiral Dopants with High Thermal Stability in Cholesteric Liquid Crystals

Abstract Azobenzene‐based chiral photoswitches are widely used as photoresponsive dopants in cholesteric liquid crystals (CLCs) due to their ability to dynamically tune supramolecular helices and have attracted considerable attention in recent years. However, a challenge for their application is the thermal instability of Z ‐isomers, causing photoaddressed images to be thermally erased at room temperature within a few hours. Here a series of new binaphthylazopyrazole chiral dopants is reported, with good bidirectional photoconversions and tunable thermal half‐lives up to two months because of the incorporated pyrazole ring with a T‐shaped Z isomer conformation. By co‐doping these switches with photoinsensitive chiral dopant S5011 into the liquid crystal host E7, photoresponsive CLCs with high thermal stability and reflective color modulation are obtained. Specifically, the tuning of reflective color across the entire visible region is achieved and the photoaddressed colorful images can be retained in dark for at least 1 week. In addition, due to the large helical twisting power variation, handedness inversion of CLCs under 365 nm light irradiation is also observed. These results provide guidance for expanding the diversity of photoresponsive chiral dopants with heteroaryl azo switches and demonstrate their great potential for developing photoresponsive CLCs with thermally stable RGB colors.