A self-healing polymer coating that changes from clear to red when damaged has been developed by a research team in the US. The coating repairs itself in sunlight, under heating or with exposure to acidic vapours, and becomes clear again.
Marek Urban, leading researcher at the University of Southern Mississippi, explains that the polymer “films are capable of sensing color changes upon mechanical scratches, but upon exposure to the visible (VIS) portion of the electromagnetic radiation (y580 nm), temperature, and/or acidic atmospheres, not only mechanical damage is repaired, but also the mechanically induced red coloured scar vanishes.”
The red colour is because of a ring-opening reaction to form merocyanine, which is red. As the ring closes again under light, heat or an acidic vapour, it forms spironaphthoxazine, which is clear.
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Self-repairable copolymers that change color
Dhanya Ramachandran, Fang Liu and Marek W. Urban
RSC Adv., 2012, Advance Article, DOI: 10.1039/C1RA00137J
