In situ mechanical reinforcement of polymer hydrogels via metal-coordinated mineralization

Over millions of years, various types of organisms have evolved the ability to synthesize exceptionally strong and tough organic-inorganic composites through cell regulated in situ mineralization of macromolecular material scaffolds.1 Borrowing inspiration from such complex biomineral material processing, we have found that metal-coordinate polymer networks can be utilized as model macromolecular scaffolds for controlled in situ hydrogel mineralization. Starting with a monodisperse metal-coordinate polymer hydrogel network, we show that metal-ion coordination crosslinks can serve as nucleation sites for mineral growth, thereby allowing significant mechanical reinforcement upon limited mineralization of the polymer hydrogel scaffold. By targeting nanoscale mineral particle growth directly at the metal-coordinate network crosslink sites, we observe simultaneous significant increases in stiffness and magnetization of the resulting hydrogels with less than 0.1 % volume of minerals. We demonstrate that the method of controlling mineralization of polymer hydrogel networks through metal-coordination is general, and therefore potentially offers a broad platform for the development of new bio-inspired organic-inorganic composite materials processing systems.