Rapid and highly efficient recombination of crosslinking points in hydrogels generated via the template polymerization of dynamic covalent three-dimensional nanoparticle crosslinkers

Dynamic covalent bonds (DCBs) can be used as crosslinking points to induce self-healing and thermoplastic properties in hydrogels because the bonding and dissociation between molecules can be controlled by external stimuli. However, once DCBs dissociate, molecules diffuse inside the gel, delaying DCB reformation. In this study, a hydrogel was prepared via template polymerization using phenylboronic acid-coated nanoparticles to control the mobility of the molecules and the density of the DCB crosslinking points. Interestingly, the loss modulus, but not the storage modulus, of the hydrogel changed with temperature according to the formation/dissociation of boronic ester bonds. Furthermore, compared with conventional hydrogels, the hydrogels prepared here exhibited very rapid changes in physicochemical properties in response to changes in temperature because the high density of three-dimensional DCB crosslinking points limits the diffusion of molecules inside the gel. As a result, the prepared hydrogel showed rapid self-healing and thermoplastic properties as the temperature changed. A novel hydrogel (TempGel(NP)) was synthesized through template polymerization of phenylboronic-acid-coated nanoparticles with tris(hydroxymethyl)methyl acrylamide (THMAAm). This process forms dynamic boronic ester crosslinks, creating a highly dense and uniform three-dimensional network. The innovative structure exhibits reversible thermal responsiveness, enabling rapid bond dissociation and reformation upon temperature changes. The dense packing around nanoparticles minimizes molecular diffusion, ensuring superior self-healing, high thermal hysteresis, and tunable viscoelastic properties. This innovative design provides a robust platform for advanced applications in smart materials, biomedical devices and responsive hydrogels.