Entropy-driven toughening and closed-loop recycling of polymers via divergent metal-pyrazole interactions.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41309603.
- Also identified by DOI 10.1038/s41467-025-65700-4 and PMC identifier 12661056.
- Licence recorded as CC BY-NC-ND.
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Abstract
Developing dynamic polymeric materials that possess closed-loop recyclability under mild conditions and outstanding mechanical properties is a highly desirable but challenging pursuit. This study presents a entropy-driven toughening strategy through divergent metal-pyrazole (DiMP) coordinations, achieving a mechanically robust and recyclable polyurethane (PU) elastomer. DiMP interactions feature multiple discrete complexes (i.e., CuL<sub>2</sub>, Cu<sub>2</sub>L<sub>2</sub>, and CuL<sub>3</sub>, where L = dipyrazole ligand) to minimize the entropy-gain mediated compensatory effect during bond dissociation and accordingly increase energy dissipation upon polymer deformation. The DiMP-crosslinked PUs (DiMPUs) exhibit an unprecedented 11-fold improvement in toughness (310.8 MJ m<sup>-3</sup>), a tensile strength of 59.0 MPa, and exceptional elastic recovery (94%), attributed to gradient energy dissipation mechanisms involving dynamic DiMP coordinations and synergistically hierarchical hydrogen bonds. Crucially, the selective acidolysis of pyrazole-urea bonds, together with the inherently weak protonation affinity of pyrazole relative to amine, allows monomers to be efficiently recovered and reengineered into virgin materials, manifesting the closed-loop recyclability. This work provides a sustainable blueprint for dynamic polymers balancing mechanical robustness and environmental circularity.