Mussel inspired self-healing materials: Coordination chemistry of polyphenols

Abstract Coordination bonds are most often reversible. Using them to crosslink polymers into for example hydrogels can therefore be expected to result in reversible crosslinks, which in turn provides self-healing properties. Polyphenols such as the catechol group of the special amino acid DOPA ( l -3,4-dihydroxyphenylalanine), which is used in mussel byssal threads to form a self-healing coating and for adhesion, are excellent coordinators of hard metal ions like iron(III). We will discuss the use of polyphenols and metal crosslinking to form self-healing hydrogels. We also treat less specific effects of metal ions on hydrogel gel mechanical properties by describing Hofmeister effects of cations on hydrogel rheological properties.