Biobased Reversible Cross-Linking Enables Self-Healing and Reprocessing of Epoxy Resins

The rapid development of thermosetting polymers contributes strongly to environmental pollution, petrochemical resource consumption, and increasing carbon dioxide emission. Introducing a reversible supramolecular cross-linking network into the thermosetting polymer to endow it with reprocessability and self-healing ability is highly attractive for the reduction of fossil fuel consumption. Despite the tremendous advancement in recyclable thermosetting polymers, using biobased materials to construct reversible cross-links, which can realize the high biomass carbon content of materials, remains challenging. Here, we present a self-healing and reprocessable epoxy resin enabled by biobased multiple hydrogen bonds between biological tannic acid and chitosan. The binding energy simulation demonstrates that effective hydrogen bonds are constructed in the epoxy resin. The resultant supramolecular cross-linked epoxy resin shows improved mechanical properties (tensile strength increased by two times, toughness increased by 2.7 times), high self-healing efficiency (104% toughness recovery) at room temperature, and excellent reprocessability (109% toughness recovery). We envision that the proposed biobased reversible cross-linking strategy will be useful in the greening and recycling of various thermosetting polymers, such as rubbers, cross-linked plastics, etc.