Dual-Mode Force-Responsive Information Encryption Enabled by Sustainable Cellulose Nanocrystal-Reinforced Waterborne Nonisocyanate Polyurethanes

Nonisocyanate polyurethanes (NIPU) have emerged as a promising alternative to conventional polyurethanes owing to their enhanced safety and sustainability across the entire life cycle. Here, we report a green waterborne NIPU elastomer toughened with cellulose nanocrystals (CNCs). In accordance with the principles of green chemistry, a tough elastomer is synthesized from renewable CNC and waste CO 2 as reactants via a simple, organic solvent-free, and safe synthetic route. Furthermore, the damaged elastomer exhibits recyclability through mechanical processing. Physical cross-links among CNC, polyethylenimine, and the NIPU matrix form multiscale microdomains that act as sacrificial bonds, thereby significantly enhancing toughness. Under mechanical deformation, the elastomer exhibits reversible birefringence-induced color changes over 0–300% strain. Meanwhile, the inherent fluorescence of the nonisocyanate backbone enables the creation of UV-activated patterns that remain invisible under ambient light. By integrating these mechanochromic and fluorescent responses, the dual-mode system creates dynamic, force-dependent encryption patterns that are only revealed under concurrent UV illumination and mechanical strain, thus enabling multilevel information encryption. This work introduces a design strategy for dual-responsive, eco-friendly polyurethanes with promising applications in anticounterfeiting, flexible displays, and advanced information storage.