Constructing High-Transparency, Self-Healing and Reprocessable Poly(thiourethane) Elastomers Based on Zn2+-Multidentate Pyrimidine Coordination.

To develop self-healing polyurethane materials with high transparency and superior mechanical performance, in this work, the poly(thiourethane) elastomers were prepared by incorporating the dynamic thiourethane bonds via thiol-isocyanate click reaction, followed by the addition of 1-(3-aminopropyl)imidazole (IZ), 3-hydroxypyridine (HP), and 2,4-diamino-6-hydroxypyrimidine (HPM) as ligands to produce three different polyurethane networks (named PTU-IZ, PTU-HP, and PTU-HPM). Zinc chloride (ZnCl2) was further introduced to construct metal-coordinated crosslinking networks, recorded as PTU-IZ-Zn, PTU-HP-Zn, and PTU-HPM-Zn, respectively. The effects of ligands and Zn2+ coordination on the materials' optical transmittance, mechanical properties, self-healing capability, and reprocessability were systematically investigated. The results demonstrate that HPM and Zn2+ will facilitate the formation of more effective crosslinking, which significantly enhances the mechanical properties of PTU-HPM from 4.61 MPa up to 9.04 MPa (PTU-HPM-Zn), while maintaining high transparency (89.0% light transmittance at 650 nm). Self-healing tests reveal that the PTU-HPM-Zn scratches can fully repair within 4 h at 70 °C. Reprocessability tests demonstrate that the internal crosslinked network of the material undergoes reversible dissociation, enabling a topological transition from a crosslinked to a linear structure and thereby imparting excellent thermal reprocessability. This study provides novel insights for the design and fabrication of high-performance transparent self-healing polyurethane materials.