p(MMA/nBA) copolymer self-healing

A sample of self-healing material mends itself after being cut by a razor blade. Credit: M. W. Urban et al./Science

Materials science

Material zips itself back together thanks to the power of attraction

The forces that hold molecules together make a severed material whole again.

A material made from commonly available industrial chemicals independently heals itself after being cut or scratched.

Such ‘self-healing’ materials have been created before. But past versions have required chemical modifications or the application of an electric or magnetic field to reknit.

To develop a self-sufficient self-healing material, Marek Urban and his colleagues at Clemson University in South Carolina developed compounds that repair themselves by harnessing the forces that hold molecules together. The team synthesized polymers — chain-like molecules made of repeated units — from two types of carbon-based chemicals called acrylates. In long stretches of the polymers, the two types of acrylate alternated. Interactions between the acrylate units caused the chains to bunch and coil.

Within about 14 hours of cutting, the material recovered more than 90% of its tensile strength, a measure of resistance to breakage. Simulations suggested that the bunched chains rebounded like a spring. That rebound allowed the sections consisting of alternating units to connect with each other.

The behaviour could be harnessed to produce new self-repairing plastics, paints and coatings.