Enhanced water retention
May 10, 2018
The change from wet and soft to dry and hard is a viscoelastic to solid material transition widely displayed in nature, in particular in materials rich in metal-coordinate crosslinking. How metal-coordinate crosslink dynamics contribute to macromolecular material mechanics upon solidification by dehydration remains an open question. Using mussel-inspired Fe-catechol crosslinked polymer hydrogels, we address this question. In addition to a nearly two-fold increase in stiffness, we find that the presence of Fe-catechol coordination bonds in a dehydrated polymer gel also provides the bulk network with a significantly increased energy dissipation with over three times higher loss factor. We present evidence to suggest that small amounts (~ 4 wt %) of locally bound water maintain the dynamic nature of Fe-catechol coordinate crosslinks in a dehydrated polymer network. The dehydration-induced polymer material mechanics presented here may provide deeper insights on the biological utilization of metal-coordinate crosslink dynamics as well as inspire new ideas on sustainable materials engineering.