A bio-based rare-earth complex for simultaneously enhancing the flame retardancy, antibacterial activity, and self-healing ability of polyurethane

The development of intrinsically multifunctional polymeric shielding materials that simultaneously integrate fire safety, mechanical robustness, self-healing capability, and radiation attenuation remains a significant challenge for advanced biomedical protection applications. Herein, this work proposes a bio-based rare-earth coordination strategy for the fabrication of a lead-free multifunctional polyurethane elastomer through the incorporation of a gadolinium–pyridoxal 5′-phosphate (PLP-Gd) coordination complex into the polyurethane molecular network. Through a systematic investigation of the thermal degradation behavior of polyurethane, the catalytic role of the PLP-Gd complex in regulating the degradation pathway and promoting char formation was revealed. Benefiting from the synergistic effects of gadolinium-based high-atomic-number shielding centers, phosphorus-containing flame-retardant groups, and dynamic coordination/covalent interactions, the resulting PLP-Gd-PU exhibits substantially enhanced overall performance. Specifically, the optimized elastomer demonstrates improved flame retardancy, with a limiting oxygen index (LOI) of 22.6%, a 62.5% reduction in peak heat release rate (PHRR), and significantly suppressed toxic smoke release. Meanwhile, the dynamic reversible crosslinking structure imparts the material with solvent-assisted repairability., achieving ahealing efficiency of 71.4% after 24 h under mild conditions. More importantly, owing to the homogeneous distribution of Gd-containing coordination units, the elastomer exhibits X-ray attenuation performance, achieving a shielding efficiency of 20.6% at 80 kVp, while maintaining high tensile strength (24.5 MPa) and durable antibacterial activity against both Gram-positive and Gram-negative bacteria. This work provides a general molecular-engineering strategy for the design of environmentally friendly, self-healable, and intrinsically integrated medical radiation-shielding polymers, offering new opportunities for next-generation smart biomedical protective materials.