Imidazolium-catalyzed dynamic ester cross-links towards reprocessable epoxy vitrimers

Ionic liquids (ILs), in particular imidazolium salts, have raised huge interest as organocatalysts in recent years but have never been considered as activators in associative covalently adaptable networks, also referred to as vitrimers. In this work, we described the first imidazolium-catalyzed vitrimers. The latter consist in epoxy-acid resins that can be reshaped and recycled through catalyzed associative transesterification reactions. A series of cross-linked epoxy-acid networks were produced in the presence of different imidazolium-acetate salts prepared by the straightforward Radziszewski multicomponent reaction. The mechanical properties and dynamics of the resulting materials were studied. Stress-relaxation experiments carried out on resins formulated with few percent of imidazolium salts highlighted the ability of the latter to promote transesterification reactions within the networks and to confer them with vitrimers' features. These imidazolium-catalyzed epoxy vitrimers were also successfully recycled several times while preserving their excellent mechanical properties. Overall, this work demonstrates the potential of ILs as catalysts in the field of adaptable networks and, given the large variety of ILs and of the IL-catalyzed reactions, this approach is likely to broaden the scope of vitrimers in the future.