Chemorheology of Phenylboronate-Salicylhydroxamate Cross-Linked Hydrogel Networks with a Sulfonated Polymer Backbone

Hydrogel networks cross-linked with polymer-bound phenylboronic acid (PBA) and salicylhydroxamic acid (SHA) demonstrate pH-reversible gel behavior due to the pH-dependent equilibrium of the cross-linking moieties that form the gel network. Furthermore, the pH at which gels behave dynamically can be controlled by use of a polyelectrolyte backbone. Here we report on the frequency-dependent chemorheological characterization of PBA-SHA cross-linked hydrogel networks with a sulfonated polymer backbone. Our results suggest that the anionic nature of the polymers allows reversible cross-linking at neutral pH that an otherwise neutral-backboned PBA-SHA cross-linked network cannot and that these charge-induced dynamics can be effectively screened by ions in solution. Moreover, moduli-frequency data can effectively be reduced into a single master curve with a neutral-backboned PBA-SHA gel data set as the reference condition.