Rational design of hydrogels relies on an in-depth understanding of the principles that govern the mechanical behaviors of biomacromolecules. Mimicking and capturing such behaviors in synthetic polymers is highly desired for many biomedical and technical applications. To elucidate quantitative correlations between viscoelastic properties and microscopic parameters, a well-defined system is required where important molecular parameters could be independently controlled. We report a dynamic hydrogel crosslinked with hydrazone bonds in the presence of an organic catalyst that could accelerate the exchange of hydrazone without affecting the network structures. The dynamics of crosslinks could be modulated in this system via catalyst concentration without affecting crosslinking density, thus quantitatively and unambiguously correlating the network parameters to mechanical properties of dynamic hydrogels. The time-dependent mechanical behavior of dynamic hydrogels are only determined by two factors: the exchange rate of crosslinks and the number of effective crosslinks per polymer chain, and are independent of polymer concentration. These observations provide a guideline to precisely tune the viscoelastic properties of these hydrogels to better mimic the time-dependent mechanics of natural systems.

Understanding and precise engineering of hydrogel mechanics via molecular parameters

ACS Spring Meeting 2021

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