Self-catalytic Preparation of Epoxy Vitrimers: Mechanical performance, Adaptivity and Recyclability

The network structure of a vitrimer can undergo associative dynamic bond-interchange reactions at high temperatures to display a certain degree of adaptivity but remain crosslinked, so it behaves like a thermoset at service temperature. Epoxy vitrimers that work via the dynamic transesterification (DTER) mechanism have received the most study. I some earlier epoxy vitrimer works, the anhydride curing agent is purposely kept stoichiometrically deficient, which results in insufficient curing and hence poor mechanical and thermal properties. High catalyst concentration is often required to ensure fast repairing and shape changing properties, which may cause some potential problems in material applications.
We has made a great effort on developing catalyst-free or internally catalyzed epoxy vitrimers. Our approach is to introduce self-catalysis into the reaction system, so both the curing of vitrimer preparation and subsequent DTER in the crosslinked polymer at elevated temperature can take place without external catalysts. It is critical to maintain sufficient hydroxyls and ester linkages in the system to enable adequately fast DTER and hence decent adaptivity. We have also investigated the simple and eco-friendly recycling of the epoxy vitrimers via hydrolysis or alcoholysis.