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A Self-healing Polymer Fills in Cracks

The days of covering your dining room table in plastic for fear of a scratch and parking your new car at the farthest reaches of the grocery store parking lot might be numbered.

Researchers at Case Western Reserve University have developed a material that repairs itself when exposed to ultraviolet light. The polymer, they say, could one day be added to a range of products to create self-healing automotive paints and varnishes for furniture and floors.

"What we've designed is essentially the ability for this polymer to disassemble on exposure to light. When it disassembles, the material reflows into the crack, and the system is healed," says Stuart Rowan, PhD, a macromolecular scientist and engineer at the Case School of Engineering who led the research team that developed the compound.

Unlike conventional polymers—which consist of long, chain-like molecules— the new compound is composed of smaller molecules, which are assembled into longer, polymer-like chains using metal ions as "molecular glue." Under intense UV light, the structures are temporarily unglued, transforming the originally solid material into a liquid that flows easily. When the light is switched off, the material reassembles and solidifies again, restoring its original properties.

The discovery was made in partnership between Rowan's team at Case Western Reserve and researchers from Switzerland's University of Fribourg and the Army Research Laboratory at Aberdeen Proving Ground in Maryland. The team's results were published in an April issue of Nature, and, though there is still a long way to go before self-healing paints and varnishes are available on the market, Rowan and his team say proving the concept works is an exciting first step

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