Oxetane

The researchers modified the chitosan slightly with the addition of the structures composed of four carbon atoms called oxetane rings. ❋ Unknown (2009)

They designed molecules joining ring-shaped molecules called oxetane with chitosan. ❋ Unknown (2009)

"The ability to combine industrially accepted and well-studied oxetane groups with a widely available renewable biomaterial such as chitosan is a powerful concept from an environmental and energy viewpoint," wrote Hawker in an e-mail exchange. ❋ Unknown (2009)

When the polyurethane is damaged, a ring of oxetane is also ripped open. ❋ Unknown (2009)

When something scratches the coating, the oxetane ring is broken. ❋ Unknown (2009)

To the chitosan precursor, the scientists added oxetane, a ringed molecule that can be broken without much energy. ❋ Unknown (2009)

It is the oxetane rings that give the material its ability to heal, says Urban. ❋ Unknown (2009)

They incorporated four-sided oxetane "rings" and a chitosan precursor into a polyurethane. ❋ Unknown (2009)

When the material is scratched, oxetane rings split, exposing reactive sites, like arms that want to grab something. ❋ Unknown (2009)

The broken chitosan rods and oxetane rings then bond with each other across the damaged area, dragging the two sides together to eliminate the scratch. ❋ Unknown (2009)

The chitosan arms and the oxetane arms attract one other, bond, and -- presto! ❋ Unknown (2009)

The remaining 0.01 percent is either a four-molecule oxetane ring or a long rod of chitosan. ❋ Unknown (2009)

Exposure to UV light creates reactive spots on sections of the chitosan molecules which then combine with the broken oxetane rings to form new chemical cross links that close up the damage. ❋ Unknown (2009)

Scratches or damage to the polyurethane coat split the oxetane rings, revealing loose ends that are highly likely to chemically react. ❋ Unknown (2009)