US materials scientist mussel in on stretchy tough elastomers

Researchers at the University of California Santa Barbara have strengthened flexible elastomers with an iron-catechol complex, using salt-water mussels as a natural inspiration for a tough viscoelastic polymer.

Polymer strengthening has long been a challenge in making tough plastic that avoids brittle characteristics. The more cross links in a polymer matrix increases impact resistance but also makes a stiffer material.

Scientists at the UCSB Materials Research Laboratory in California, USA, investigated the threads mussels use to cling to rocks. The byssal threads are of a natural polymer, collagen, which flex but avoid breaking. Researchers Emmanouela Filippidi and Thomas R. Cristiani, published ‘Toughening elastomers using mussel-inspired iron-catechol complexes,’

In the October 27 issue of the journal Science. Professor Megan Valentine, study author, said: “In the past decade, we have made tremendous advances in understanding how biological materials maintain strength under loading. In this paper, we demonstrate our ability to use that understanding to develop useful manmade materials. This work opens exciting lanes of discovery for many commercial and industrial applications.”

The team synthesised an amorphous, loosely cross-linked epoxy network and treated it with iron to form dynamic iron-catechol cross-links.

Without iron, a link stays broken if impacted, but with reversible iron-catechol coordination bonds, cross-linked bonds can reform. The material is both stiffer and tougher than similar networks lacking iron-containing coordination bonds.