Dual‐direction Circularly Polarized Luminescence Materials With On‐demand Handedness and Superior Flexibility

Abstract This work utilizes the self‐assembled cellulose nanocrystals (CNCs) as the host chiral template and fabricates a circularly polarized luminescence (CPL) film. By manipulating the photonic bandgap, the synthesized film integrates a strong CPL signal and superior mechanical flexibility. Without losing the CPL activity, the ultimate strain of 19% has exceeded most CNC‐based chiral luminescent assemblies, which enables them candidates in the optical sensor and wearable device. Meanwhile, the film has a humidity‐stimulus CPL response, with the dissymmetry factor (g_lum) close to 0.51. This responsive process is reversible and the optical properties can recover upon drying. Next, by manipulating the optical pathway, this work achieves on‐demand CPL direction control and meets the considerable intensity of reversed optical signals (g_lum: ‐0.35), avoiding the structure disruption and direction random under the external stimuli, which opens a new insight into the optical regulations. Furthermore, this work combines the in situ growth strategy and first synthesizes the dynamic‐switchable dual‐direction CPL film. Optics in both directions can be inverted simultaneously by exchanging the growth sequences. Finally, multimodal optics, excellent stability, and green manufacturing make them welcome in the advanced anti‐counterfeit areas, with the features of lossless and long‐time useful.