Reversible optical and self-healing properties of fluorine containing epoxy coatings with azobenzene

Abstract

The demand for intelligent materials with advanced functionalities, particularly light-sensitive materials like azobenzenes, has surged in various industries. These molecules exhibit rapid, reversible responses to stimuli, enabling significant alterations in the optical and physical properties of polymer matrices. In a previous study, epoxy coatings were synthesized using polyurethane precursors modified with 4-phenylazophenol (AZO) and fluorinated species (EPU and EPUF). The present work focuses on the optical and selfhealing properties of these epoxy coatings, specifically driven by the UV–visible light responsiveness of AZO. Significant color changes were observed in the materials after light exposure, as confirmed by colorimetric and spectroscopic analyses. This rapid color transition is attributed to the efficient isomerization of the AZO groups, which enables the coatings to retain their chromatic and energetic properties over extended periods. A practical application of this phenomenon was demonstrated in a reversible writing process, where messages could be displayed on the surface for a controlled period before being erased. Furthermore, the incorporation of the AZO derivative enabled light-induced self-healing. This mechanism was triggered by UV light irradiation. The integration of fluorinated chains reduced the surface energy of the system, enhancing the efficiency of irradiation and prolonging the cis isomer's stability. This improvement granted the material superior photochemical control, resulting in a faster and more efficient process. These findings position these materials as promising candidates for coatings in technologically advanced applications as dynamic tools for temporary displays and information encoding.