Hybrid Waterborne Polyurethane/Graphitic Carbon Nitride Nanosheet Films for Self-Cleaning and Anti-Bacterial Applications

The self-cleaning and antibacterial properties of waterborne polyurethane (WPU) films are realized by constructing a micronano structure on its surface via the controlled aggregation of graphitic carbon nitride (g-C3N4) nanosheets. Based on the hydrogen bonding between the C═O groups in WPU and NH- groups in g-C3N4, the g-C3N4 nanosheets can be well dispersed in the WPU films. Further increasing the concentration of the g-C3N4 nanosheets in the WPU dispersion during the coating causes the enrichment of the g-C3N4 nanosheets, triggering a minor aggregation and forming a concave-like structure with nm to μm scale on the surface. Due to the photocatalytic capability of the g-C3N4 nanosheets, free radicals are formed when exposed to visible light illumination, which, together with the large specific surface area of the micronano structure, decompose common stains on the WPU surface. More than 95% of daily lives stains, such as soy sauce, can be removed from the hybrid WPU films with micronano structure on the surface after exposure to visible light for only 1 h. Besides hydrophilic stains, the hybrid WPU films with micronano structure on the surface are also highly resistant against lipophilic stains and exhibit antibacterial properties. 99.8% of S. aureus bacteria and 100% of E. coli bacteria can be efficiently killed on the hybrid WPU film surface after exposure to visible light for 2 h. Based on these unique properties, the hybrid WPU films with micronano structure on the surface are highly suitable for the interiors of cars, indoor furniture, or faux-leather garnets.