Photoinduced Two-Dimensional Supramolecular Chiral Microstructures with Enhanced Stability

Abstract

Periodic microstructures are essential for controlling optical and mechanical properties but remain difficult to fabricate with precision and scalability, and conventional methods are costly and rigid. Thus, self-assembling and tunable alternatives are needed. Stimulus-responsive anisotropic soft matter offers a promising solution because it can spontaneously form micro- and nanoscale periodic superstructures with high tunability for functional device design. However, these superstructures rely on a delicate balance of multiple forces, so they are vulnerable to external perturbations and often have a short lifespan, which is a key challenge in the field. This study investigates photoinduced Helfrich deformation in chiral azobenzene-doped cholesteric liquid crystals (CLCs) and compares the resulting microstructures in systems with and without bent-mesogenic dimers. The dimers exhibit an exceptionally low bend elastic constant that governs the resistance of the LC system to bending deformation. During the cis-trans photoisomerization of chiral azobenzene, stress accumulation due to the shortening of the helical pitch, leading to the formation of a two-dimensional supramolecular chiral microstructure. Furthermore, applying an auxiliary voltage lower than the threshold of the electro-induced Helfrich deformation considerably enhances the stability of the microstructure, and the stabilization effect increases in the samples containing dimers. At voltages lower and higher than the threshold, the microstructures eventually transform into a planar state and a hybrid state with fingerprint and focal conic textures, respectively. This study opens a new avenue for expanding the applicability of Helfrich deformation and provides insights into the stability control of periodic microstructures in soft matter physics, providing valuable reference for the fields of optics and photonics.