(420c) Towards a Mechanistic Understanding of Associative Covalent Adaptable Networks

Vitrimers are a new class of thermosetting polymers that contain dynamic covalent bonds that undergo associative exchange processes. Under elevated temperatures, these bonds can rearrange, modifying the topology of the material without changing the crosslink density. These materials, while covalently crosslinked, can act as viscoelastic fluids at higher temperatures, enabling characteristics such as recyclability and self-healing. The relationship between molecular exchange chemistry and network properties remains poorly defined. By studying conjugate addition-elimination reactions of thiols with various crosslinkers in small-molecule model systems and in networks, we aim to understand how the molecular exchange kinetics affect vitrimer stress relaxation and bulk properties. We explore how changes in reactivity on a molecular scale is translated into macroscopic responses in polymer networks. Overall, our results provide deeper insight into how the time-dependent mechanical properties of vitrimers are influenced by the molecular exchange reactions.