Conjugated Aryl Modified Naphthopyran Derivatives for Fast‐Response Photochromic Polyurethane Composite Coatings

ABSTRACT Naphthopyran is a classic organic photochromic functional dye that has garnered significant research attention due to its excellent comprehensive properties. Its photochromic behavior is primarily determined by its molecular framework structure and the surrounding host medium environment. In this study, three novel purple naphthopyran derivatives were specifically designed and synthesized. It was found that introducing conjugated aromatic substituents such as 4‐fluorophenyl, 4‐trifluoromethylphenyl, and phenylethynyl at the 14‐position of the naphthopyran core significantly enhances the UV response speed and thermal fading rate of the dyes; moreover, larger molecular conjugation systems result in faster fading kinetics. By incorporating these dyes as core photochromic functional units into polyurethane prepolymer solutions and precisely controlling the ratios of prepolymer components, soft/hard segments, and the synthesis formulation, multifunctional photochromic polyurethane coatings with high color‐changing sensitivity, excellent cycling stability, and superior adaptability can be prepared.