Bio-based non-isocyanate polyurethane with clusteroluminescence, self-healing, and closed-loop recyclability

Bio-based non-isocyanate polyurethanes (NIPUs) have attracted considerable research interest owing to their environmentally benign synthesis routes and alignment with the principles of sustainable materials development. In this study, bio-based non-isocyanate polyurethanes (D-NIPUs) exhibiting clusteroluminescence, self-healing capability, and full recyclability were synthesized at atmospheric pressure using binary cyclic carbonates and bio-based diamines as feedstocks. By adjusting the molecular weight of the diamine, the mechanical properties of D-NIPUs can be systematically controlled. Among them, D-NIPU1 exhibits excellent mechanical properties, with a tensile strength of up to 15 MPa. Owing to the reversible hydrogen-bonding network formed by the high density of amide and urethane linkages along the polymer backbone, as well as the dynamic transcarbamoylation reaction between hydroxyl and carbamate groups, D-NIPU3 exhibits exceptional autonomous self-healing capability, achieving over 90% recovery of tensile strength after 8 h of thermal healing at 90 °C. Moreover, D-NIPUs can undergo controlled chemical degradation in ethanol via the transcarbamoylation reaction, yielding oligomeric species that can be directly repolymerized to establish a closed-loop recycling system. After three consecutive degradation–repolymerization cycles, the recycled D-NIPU3 retained 87.6% of its initial tensile strength. Notably, D-NIPUs contain no conventional chromophores, yet they exhibit significant UV-induced fluorescence. This is due to clusteroluminescence arising from carbamate groups with restricted molecular motion. This study proposes a promising strategy for designing sustainable NIPUs that integrate green synthesis, functional integration, and recyclability via chemical degradation, offering broad application prospects in coating applications such as electronic waste recycling, self-healing packaging for flexible electronics, and green anti-counterfeiting.