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<p>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.</p>

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Entropy-driven toughening and closed-loop recycling of polymers via divergent metal-pyrazole interactions

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年11月27日

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  • Lei Huang,
  • Jiujie Xia,
  • Zeyuan Jin,
  • Xinman Hu,
  • Xiping Chen,
  • Ning Zhao,
  • Changyou Gao,
  • Wenxing Liu

摘要

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., CuL2, Cu2L2, and CuL3, 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−3), 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.