Search

In general, mechanical properties and gelation kinetics exhibit a positive correlation with the amount of gelation reagents used. Similarly, for catechol-containing hydrogels, which have attracted significant attention, because of their unique dual properties of cohesion and adhesion, increased amounts of cross-linking agents, such as organic oxidants and/or transition metals (Fe3+), result in enhanced mechanical strength and more rapid gelation kinetics. Here, we report a new metal–ligand cross-linking chemistry, inspired by mussels and ascidians, that defies the aforementioned conventional stoichiometric concept. When a small amount of vanadium is present in the catechol-functionalized polymer solution (i.e., [V] ≪ [catechol]), organic radicals are rapidly generated that trigger the gelation reaction. However, when a large amount of the ion is added to the same solution (i.e., [V] ≫ [catechol]), the catechol remains chemically intact by coordination that inhibits gelation. Thus, a large amount of cross-...