Room-Temperature Self-Healing and Reprocessable Waterborne Polyurethane with Dynamically Exchangeable Disulfide Bonds

Recently, covalent adaptable networks (CANs) based on dynamic exchange reactions have been synthesized, and the research on these materials has been mainly focused on the self-healing behavior and reprocessing properties of CANs. Disulfide bonds can be considered to be a type of dynamic reversible covalent bonds, and exchange reactions of disulfide bonds proceed easily at mild temperatures, which endow materials containing disulfide bonds with self-healing properties and the reprocessability under suitable conditions. Herein, we synthesized a type of waterborne polyurethane (WPU) CAN incorporated with disulfide bonds. A reasonable structural design was used in conjunction with a self-healing kinetic analysis to predict that the highest performing CWPU-8 sample could repair a microcrack at room temperature, which was verified by optical microscopy observations combined with self-healing mechanics. The most important feature of this material is its reprocessing property, which was investigated by rheology tests. These assessments demonstrate that the self-healing behavior and the reprocessability are closely related to exchange reactions of disulfide bonds, and the structure-property relationship provides deep insights into the CANs chemistry.