Predictably Engineering the Viscoelastic Behavior of Dynamic Hydrogels via Correlation with Molecular Parameters

Area of Science:

• Materials Science
• Polymer Chemistry
• Rheology

Background:

• Designing dynamic hydrogels with predictable viscoelastic properties requires understanding the link between molecular characteristics and bulk behavior.
• Dynamic covalent chemistry offers a route to create adaptable hydrogel networks.

Purpose of the Study:

• To quantitatively elucidate the principles governing the viscoelastic behavior of dynamic hydrogels.
• To establish a correlation between molecular parameters and macroscopic viscoelastic properties.

Main Methods:

• Synthesized dynamic covalent hydrogels crosslinked via hydrazone bonds.
• Independently tuned the exchange rate of hydrazone bonds using catalyst concentration, while keeping crosslinking density constant.
• Analyzed the viscoelastic response as a function of network parameters.

Main Results:

• Identified that terminal relaxation time is determined by crosslink exchange rate and effective crosslinks per chain, independent of network architecture.
• Established a universal correlation between terminal relaxation time (from stress relaxation) and crosslink exchange rate (from reaction kinetics).

Conclusions:

• The findings provide a quantitative framework for designing dynamic hydrogels with tailored viscoelastic responses.
• The identified universal correlation can be generalized to various viscoelastic hydrogel networks.
• This work facilitates the rational design of hydrogels for specific applications based on molecular control.