Durable Anti‐fogging Polymer Coatings Based on C,H Insertion Cross–linking (CHic) That Are User and Environmentally Friendly

Abstract Fogged surfaces, such as bathroom mirrors, quickly become a nuisance in everyday life, but are particularly problematic in safety‐relevant and medical areas. Present approaches are often based on hydrophilic coatings, which can prevent fogging, but are not very durable. Surface‐attached polymer networks that can be quickly and easily prepared from thin films of prepolymers by photochemical activation using brief irradiation with ambient light are presented. This novel photoreactive copolymer contains ionic, hydrophilic repeating units and hydrophilic nitro‐substituted phenyl diazo ester moieties. The diazo groups in the prepolymer films form carbenes after excitation, which then bind to adjacent chains and to the substrate by C,H insertion cross–linking (CHic). The resulting surfaces exhibit excellent anti‐fogging properties as they allow water to condense into a uniform thin film. The substrates remain highly transparent, even after frequent washing. In addition, the polymers can also be easily applied to previously damaged coatings by soiling in order to fully restore the anti‐fog properties. Due to the solubility of the prepolymers in water, the easy cross–linking in sunlight, the durability of the coating, and the possibility of damage repair, the polymers are suitable for easy‐use scenarios by non‐professionals, which offers great potential for such an approach.