Bio-Based Polyurethane–Urea with Self-Healing and Closed-Loop Recyclability Synthesized from Renewable Carbon Dioxide and Vanillin

Developing recyclable and self-healing non-isocyanate polyurethane (NIPU) from renewable resources to replace traditional petroleum-based polyurethane (PU) is crucial for advancing green chemistry and sustainable development. Herein, a series of innovative cross-linked Poly(hydroxyurethane-urea)s (PHUUs) were prepared using renewable carbon dioxide (CO₂) and vanillin, which displayed excellent thermal stability properties and solvent resistance. These PHUUs were constructed through the introduction of reversible hydrogen and imine bonds into cross-linked polymer networks, resulting in the cross-linked PHUUs exhibiting thermoplastic-like reprocessability, self healing, and closed-loop recyclability. Notably, the results indicated that the VL-TTD*-50 with remarkable hot-pressed remolding efficiency (nearly 98.0%) and self-healing efficiency (exceeding 95.0%) of tensile strength at 60 °C. Furthermore, they can be degraded in the 1M HCl and THF (<i>v</i>:<i>v</i> = 2:8) solution at room temperature, followed by regeneration without altering their original chemical structure and mechanical properties. This study presents a novel strategy for preparing cross-linked PHUUs with self-healing and closed-loop recyclability from renewable resources as sustainable alternatives for traditional petroleum-based PUs.