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Epoxy coatings with memory: light-induced colour change and self-healing thanks to azobenzene
A research team has developed an intelligent epoxy coating that reacts to UV light: it reversibly changes colour, displays temporary images and heals itself. This is made possible by azobenzene and fluorinated polyurethane precursors.
Researchers from Argentina have presented a novel epoxy coating that reacts to UV–visible light with reversible colour changes and also has self-healing properties. The coatings are based on polyurethane precursors functionalised with azobenzene derivatives (4-phenylazophenol, AZO) and fluorinated groups. The aim of the study was to analyse the light-induced optical and mechanical properties of the formulations.
The results showed that the materials change colour significantly and reversibly under the influence of light – caused by the trans-cis isomerisation of the azobenzene groups. This effect could be used specifically to temporarily ‘write’ information onto the surface and then delete it again. Colour measurements and spectroscopic analyses confirm the stability and repeatability of this process over longer periods of time.
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Light-controlled self-healing through azobenzene isomerisation
In addition to optical reversibility, azobenzene also enables light-induced self-healing. UV radiation triggers internal rearrangement processes that promote the repair of small areas of damage. The incorporation of fluorinated chains improves the surface properties of the system: the reduced surface energy promotes light efficiency and stabilises the cis form of the azobenzene compounds. This makes self-healing faster and more controlled.
The system described opens up potential for advanced coatings, especially in areas where temporary information display, data storage or interactive surfaces are required – for example in sensor technology, security printing or decorative applications.
Source: Progress in Organic Coatings, Volume 200, March 2025, Article 109029
