Tuning vitrimer mechanics with prepolymer and crosslinker structure

Dynamic covalent polymer networks in which the topology is reconfigured through associative exchange reactions are known as vitrimers. These materials hold promise as repairable and recyclable thermosets and elastomers. A hallmark of vitrimers is the Arrenhius relationship between viscocity and temperature; the activation energy for stress relaxation is often used to describe the energetics of the reconfiguration process. However, the mechanistic interpretation of this activation energy and its relationship to the associative exchange event are often unclear. We combine physical organic approaches and mechanical characterization to correlate the activation energy for stress relaxation to molecular reactivity and macromolecular structure. This study is enabled by the use of crosslinks that exchange via a catalyst-free conjugate addition/elimination pathway.