Do bio-inspired metal-coordination crosslink dynamics offer anything new for engineers of hydrogel mechanics?

Efforts to engineer synthetic polymer hydrogel mechanics is increasingly coupled to the design of transient crosslink dynamics. Based on the growing evidence supporting a critical role in desirable material applications in nature, bio-inspired metal-coordinate transient crosslinking might provide unique opportunities in these efforts. Using simple metal-coordinating polymers, we have sought to gain a deeper understanding of whether polymer hydrogel mechanical properties can be controlled over multiple hierarchical time-scales via design of metal-coordinate crosslink structure on multiple length-scales. Specifically, by utilizing metal ion-coordination complexes and metal nanoparticle-coordination junctions as supra-molecular crosslink structures, we have obtained easy access to control over network dynamics on the microscopic scale, and thereby unique opportunities to broadly shape the distribution of network stress relaxation on the macroscopic scale. Our findings suggest that bio-inspired metal-coordination crosslink dynamics can indeed be utilized to engineer complex gel mechanics directly via simple design of supramolecular crosslink structure, and could help improve our understanding of and control over spatio-temporal molecular hierarchy in loadbearing biological and bio-inspired materials.