Supramolecular Processing and Covalent Locking: Scalable Room-Temperature Fabrication of Mechanically Robust Structurally Colored Composite Films

Scalable fabrication of structurally colored composite films (SCCFs) integrating facile processability, mechanical robustness, and environmental stability remains a critical challenge. Herein, a supramolecular processing and covalent locking strategy to address this bottleneck is proposed, enabling the room-temperature production of cross-linked SCCFs (C-SCCFs) from commercially available materials. This approach leverages dynamic supramolecular interactions between SiO₂ colloidal particles and a cross-linkable methacrylated polyethylenimine (PEI-MA) to facilitate rapid, shear-induced colloidal ordering. Subsequent UV-triggered covalent cross-linking of methacrylate groups permanently locks this ordered structure into a dense covalent network. Optimization of cross-linking density and colloid volume fraction provided a balance between flexibility, strength, and optical intensity. The resulting C-SCCFs exhibit high optical reflectance, tunable colors, and excellent mechanical robustness, withstanding over 12,000 bending cycles and multiple swelling-drying processes. Furthermore, we demonstrate the versatility of this platform by creating laser-engraved patterns, conformal coatings on 3D surfaces, and durable integrations with textiles. This work establishes a general and scalable route to high-performance photonic materials, paving the way for applications in wearable technology, anticounterfeiting, and smart coatings.