Thermal-Driven Self-Healing and Recyclable Waterborne Polyurethane Films Based on Reversible Covalent Interaction

By introducing novel stimuli-responsive Diels–Alder (DA) diol into polymer chains, a series of environmentally friendly, self-healing, and recyclable waterborne polyurethanes based on DA/retro-DA reactions (WPU-DA-x) were successfully prepared through a modified acetone process. The properties and appearance of the resultant WPU-DA-x latex were analyzed by considering particle size and zeta potential which show these dispersions with an outstanding storage stability. Simultaneously, the molecular mechanism of the self-healing behavior was extensively investigated via 1H NMR, FT-IR, and UV–vis spectroscopies exhibiting effective reversibility of the DA/retro-DA chemistry. Moreover, WPU-DA-x films with outstanding mechanical performance show an excellent self-healing capability due to the couple/decouple process of the DA reactions, and the self-healing process was qualitatively and quantitatively studied. At the same time, the networked WPU-DA-x could be recycled via hot-pressing and solution casting. At last, the thermal stability of WPU-DA-x films was distinctly enhanced, as shown by the TGA results. The fruitful outcomes indicate that WPU-DA-x exhibited a great potential application as a smart material.