Self-healing polymers mend themselves by reforming broken cross-linking bonds. However, the cross-linking healing mechanism usually requires an external stimulus.
Triggers to promote bond repair include energy inputs, such as heat or light, or specific environmental conditions, such as pH. Self-healing polymers that can spontaneously achieve quantitative healing in the absence of a catalyst have never been reported before, until now.
Ibon Odriozola previously came close when his group at the CIDETEC Centre for Electrochemical Technologies in Spain developed self-healing silicone elastomers using silver nanoparticles as cross-linkers. Unfortunately, an applied external pressure was required and the expensive silver component disfavoured commercialisation. But now they have achieved their goal to prepare self-healing elastomers from common polymeric starting materials using a simple and inexpensive approach.
An industrially familiar, permanently cross-linked poly(urea–urethane) elastomeric network was demonstrated to completely mend itself after being cut in two by a razor blade. It is the metathesis reaction of aromatic disulphides, which naturally exchange at room temperature, that causes regeneration.
David Mecerreyes, a polymer chemistry specialist at the University of the Basque Country in Spain, sees opportunities to use this elastomer to improve the security and duration of many plastic parts, for example in cars, houses, electrical components and biomaterials.
‘The introduction of a room temperature exchangeable covalent bond in classic thermoset elastomers provides unique autonomous self-healing abilities without comprising the pristine material properties,’ says Richard Hoogenboom, head of the Supramolecular Chemistry group at Ghent University in Belgium. ‘Close resemblance of this novel self-healing thermoset elastomer with current commercial materials makes it highly interesting for extending the lifetime of such materials.’
Future work by the group will concentrate on stronger polymeric materials as the current poly(urea–urethane) composite is relatively soft.
Self-healing materials like this would be useful in so many places. They could keep tablets, phones and other everyday objects from sustaining nicks and scratches. Even NASA studies self-healing materials because they could reduce the need for costly and dangerous repairs in tough environments, i.e., space. Many labs around the world are working on different versions of this; last November, we reported on a self-repairing material that also conducts electricity.
The material shown above, invented by a team of materials scientists from the IK4-CIDETEC Research Center in Spain, is one of the first that is able to heal itself without the help of heat, light, added chemicals or other interventions, according to Chemistry World. (Self-healing materials often need some kind of catalyst to trigger the changes in chemistry required to bond broken pieces back together again.)
The material's creators published a paper about their work today in the journal Materials Horizons.
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