A network of loosely-linked polymers mimicking a mussel's adhesive qualities offers a way to make materials that are both strong and flexible, elements that have been widely sought but hard to produce. The conventional approach of reinforcing polymers includes the use of fillers, and results in a trade-off between stiffness and stretchiness. While recent techniques that distribute energy throughout a material (like interlacing networks, or employing reversible cross-links) offer enhanced results when used together, such improvements have been limited to soft and low-elastic dry networks. Mussels have long been an inspiration for developing adhesives that work when wet, usually by including an organic compound with a chemical signature called a catechol group. Here, Emmanouela Filippidi and colleagues produced a highly-extendable polymer-based material akin to a mussel's adhesive features (specifically, the byssal plaque and thread) by modifying several catechol groups, which they accomplished via the addition of iron molecules. The iron molecules created a reversible and load-bearing network that was 770 times stiffer and 92 times tougher than its untreated precursor. This result enabled the scientists to create a material that was strong, yet elastic. They say that their approach may be combined with existing polymer-hardening mechanisms, thus paving the way to other modifications and broad applications in structural, biomedical and aerospace materials. A related Perspective by Winey et al. delves into the findings further.
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Science