Dynamic covalent adhesives and their applications: Current progress and future perspectives

Thanks to the lightness and suitability for dissimilar material joining, adhesives are increasingly used to replace welding and bolted connections, but disassembly challenge and inadequate mechanical performance limits their applications in certain scenarios. In recent years, the employment of dynamic covalent bonds for the design of adhesive materials with high adhesion strength and recycling properties has become a research focus. This review aims at summarizing the current progress of dynamic covalent adhesives and reviewing the promising applications. Firstly, mechanisms of dynamic covalent bonds rearrangements caused by stimulation are discussed. It can be summarized as low activation energy reversible reactions activated by factors such as temperature, light, pH, etc. Then, current strategies for designing dynamic covalent adhesives in terms of improving adhesion strength and recycling property are reviewed. As for dynamic covalent adhesives design, incorporating various dynamic covalent bonds into polymer networks are stressed, and the mechanisms of dynamic covalent cross-linking for enhancing adhesion strength and recycling properties are discussed in detail. Multiple dynamic covalent bonds are also summarized for reducing the activation energy of dynamic covalent adhesives to regulate activation conditions. In addition, promising applications of dynamic covalent adhesives in the fields of energy, manufacturing, medicine and electronics are briefly elucidated. At last, future perspectives are provided for designing adhesives with high adhesion strength and climate resistance by dynamic covalent cross-linking.