Designing Dynamic Hydrogels: The Interplay of Cross-Linker Length, Valency, and Reaction Kinetics in Hydrazone-based networks

While the relationship between rate and equilibrium constants (REC’s) and bulk mechanical properties is increasingly explored, less known is the effect of network topology or cross-linker length on both REC’s and mechanical properties in dynamically cross-linked hydrogels.

Here, we chose hydrazone formation as a model system for dynamic covalent network formation. Using mono- and bi-valent hydrazides with molecular weights of 0.1–20 kg·mol-1, we show that their chemical reactivity with a small molecule aldehyde is largely unaffected by their length. However, the apparent reactivity between two polymeric macromers revealed a decade reduction in k1 and Keq compared to the model system.