Mussel inspires development of stronger and stretchier polymers

Typically, the strength of a polymer is improved by increasing the number of chemical cross-links that hold together the material’s network of polymer strands. However, binding the strands more closely together also makes the polymer more brittle, reducing its stretchiness.

A group at the University’s Materials Research Laboratory claims to have developed a method for overcoming this trade-off that’s based on the tough, flexible polymeric byssal threads that marine mussels use to secure themselves to rocks.

To develop the material, the team synthesised an amorphous, loosely cross-linked epoxy network and then treated it with iron to form dynamic iron-catechol cross-links. In the absence of iron, when one of the covalent cross-links breaks, it is broken forever, because no mechanism for self-healing exists. But when the reversible iron-catechol coordination bonds are present, any of those iron-containing broken cross-links can reform, not necessarily in exactly the same place but nearby, thus maintaining the material’s resiliency even as its strength increases.