Reprocessable Epoxy Resins Based on Hydroxy-Thioester and Thiol-Thioester Dual Exchanges

Epoxy resins are widely used due to their excellent physical and mechanical properties; however, their recycle and reprocessing remain challenging up to now. This problem may be solved by incorporating dynamic covalent cross-links into epoxy resins, and thus they have the potential to increase their service lifetimes and reduce their environmental impact. This work innovatively proposes the introducing of thioester groups into epoxy resins. Under proper conditions, the thioester will exchange with the hydroxyl groups of epoxy E51, which will produce thiol and ester groups. Then, the thiol-thioester exchange will be triggered subsequently. The proposed hydroxyl-thioester and thiol-thioester dual exchanges endow the epoxy materials with reprocessability. We designed model experiments to demonstrate the exchange capacity of hydroxyls/thioesters and thiols/thioesters under mild conditions. New epoxy resin materials have been developed based on thioester-containing curing agents. The reprocessing of the thioester-containing epoxy resin was very simple and efficient. After three reprocessing cycles, the mechanical properties of the epoxy resin material were comparable to the pristine material. In addition, the reprocessing epoxy materials had excellent shape memory properties. This work provides new ideas for the development of epoxy resins and opens up a new pathway for the application of thioesters.