Biomimetic Mechanically Robust Chiroptical Hydrogel Enabled by Hierarchical Bouligand Structure Engineering

Abstract

Natural bouligand structures enable crustacean exoskeletons and fruits to strike a combination of exceptional mechanical robustness and brilliant chiroptical properties owing to multiscale structural hierarchy. However, integrating such a high strength-stiffness-toughness combination and photonic functionalities into synthetic hydrogels still remains a grand challenge. In this work, we report a simple yet general biomimetic strategy to construct an ultrarobust chiroptical hydrogel by closely mimicking the natural bouligand structure at multilength scale. The hierarchical structural engineering of long-range ordered cellulose nanocrystals’ bouligand structure, well-defined poly(vinyl alcohol) nanocrystalline domains, and dynamic interfacial interaction synergistically contributes to the integration of high strength (23.3 MPa), superior modulus (264 MPa), and high toughness (54.7 MJ m–3), as well as extraordinary impact resistance, which far exceed their natural counterparts and synthetic photonic hydrogels. More importantly, seamless chiroptical and solvent-responsive patterns with high resolution can also be scalably integrated into the hydrogel by localized manipulation of the photonic band, while maintaining good ionic conductivity. Such exceptional mechanical-photonic combination holds tremendous potential for applications in wearable sensors, encryption, displays, and soft robotics.