Time-Temperature-Chemistry Superposition in Dynamic Covalent Networks

The incorporation of dynamic covalent bonds (DCBs) within polymer networks enables opportunities to access both elastic mechanics for material stability and viscous flow for reprocessing by controlling bond exchange kinetics. While this presents significant opportunities to access recyclable thermosets or to facilitate advanced manufacturing, there remains a lack of fundamental understanding of connecting the chemical details of molecular-scale exchange reactions to bulk thermomechanical properties. In this work, we will discuss recent efforts in our lab to link the rheological behavior at varying amplitudes and frequencies to underlying chemical mechanisms of exchange using model systems where the loading or species of catalyst can be used to tune bond exchange in chemically-identical networks. We show that for the case were exchange mechanism and first-order kinetics are preserved, rheological data can be collapsed using ‘time-temperature-chemistry’ superposition that can capture dynamics over six orders of magnitude. Collectively, these results demonstrate new ways to predictably control dynamic covalent exchange and offer insights into how to rationally design systems with the desired viscoelasticity, with implications for plastics recycling, additive manufacturing, and smart materials.