Laser-Inscribable, Moisture-Responsive Cellulosic Supramolecular Structures with Tunable Broadband Coloration

Adaptive photonic films in response to external stimuli have broad applications in optical communications, sensing, and anticounterfeiting. Yet, it remains challenging to develop photonic structures with tailorable fine patterns that display broadband color changing under ambient conditions. Here a hydrogen-bonded supramolecular cholesteric liquid crystalline polymer (CLCP) that is mediated by a binary solvent consisting of citric acid (CA) and water is presented. The incorporation of CA not only improves the long-range order of CLCPs through evaporation-induced self-assembly but is also capable of tuning their helical pitch across the entire visible spectrum. The extent of hydration-induced pitch expansion can be further manipulated by thermal crosslinking, enabling a unique patterning strategy based on mask-free, programmable laser inscription. High-precision photonic patterns are created onto CLCPs, which reveal themselves upon hydration in high visual contrast. The study offers a feasible and up-scaling route toward tailoring environmentally adaptive CLCPs with tunable broadband coloration and highly programmable photonic patterns.