Research on UV-curing waterborne polyurethane for enhancing the color fastness of structural color fabrics

Structural color fabrics, which derive their color from the periodic microstructure of photonic crystals (PCs), face a significant challenge in practical applications due to their poor color fastness. The colloidal arrays are prone to collapse under external mechanical forces such as washing and rubbing. Surface encapsulation with polymer presents a promising solution. However, the prevalent use of commercial adhesives with ill-defined compositions hinders the precise understanding and control over the relationship between material properties and color stability. To address this limitation, this study designed and synthesized the UV-curable waterborne polyurethane (UVWPU) with tailored microphase-separated structures by regulating the NCO/OH molar ratio (R value). The synthesized UVWPU emulsions exhibited a translucent light blue appearance, nanoscale particle size, and excellent stability. The cured films demonstrated high transparency (>98 %), tunable mechanical strength, and good water resistance. These UVWPUs were then applied to encapsulate structural color fabrics fabricated by shear-induced assembly of polymethyl methacrylate (PMMA) microspheres of various sizes. The resulting structural color fabrics maintained vivid, angle-dependent structural colors. More importantly, they exhibited dramatically enhanced color fastness, successfully withstanding 45 min of washing, 100 rubbing cycles, 20 bending cycles, extended storage, and exposure to acidic, alkaline, and saline environments without significant color degradation. This work provides a fundamental and practical approach for developing high-durability structural color textiles.