Fig. 4. Rehabilitation of damaged HBPU–DMPA–[Fe(DOPA)3] in seawater. (a) Virgin polymer network. (b) Damaged polymer network containing ruptured (i) covalent bonds and (ii) catechol–Fe3+ crosslinks at the interface. (c) Reconnection of the damaged polymer network through formation of catechol–Fe3+ bonds at the interface with the aid of dynamic catechol–iron interactions. Note: the iron ions and macromolecules are color coded in this way (i) to distinguish the substances located at different sides of the material, and (ii) to highlight the dynamic rearrangement of the damaged networks during healing with the aid of the mobile iron ions.
