Photoresponsive Helicity Control in Cholesteric Liquid Crystals Using a Chiral Arylazopyrazole Dopant: Chirality Amplification and Helix Inversion

We report the design and synthesis of a novel chiral arylazopyrazole (AAP) molecular switch, which exhibits robust photoresponsive behavior in nematic liquid crystal (LC) hosts. By integrating both cholesterol and AAP moieties, the dopant induces significant reorganization in cholesteric liquid crystals (CLCs), leading to unprecedented control over helical pitch and chirality. Upon UV irradiation, the dopant undergoes efficient trans (E) to cis (Z) photoisomerization, resulting in substantial changes in helical twisting power (HTP) across various nematic LC hosts such as 5CB (4-cyano-4′-pentylbiphenyl), DON-103, and ZLI-1132. Notably, the AAP-based dopant in DON-103 demonstrates a remarkable increase over 200% of HTP in Z-rich state, while in ZLI-1132, we observe a light-induced helix inversion, the first of its kind for this class of dopants. Based on the large rotational reorganization of the cholesteric helix including its inversion as well as HTP switching, we could dynamically control surface spiral textures in micro CLC droplets using UV and visible light.