Catalyst-mediated yet catalyst-free hydrogels formed by interfacial chemical activation.

We introduce an entirely new method for forming hydrogels, wherein the formation is triggered by a catalyst, but the resulting hydrogels are catalyst-free. We unexpectedly found that a sufficient amount of crosslinkable catecholquinone/semiquinone free radicals is generated by the physical contact between catechol-containing polymers and surface-immobilized catalysts.