Effect of ligand bond structure on self‐healing properties of XNBR / CuCl 2 at different temperatures

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Abstract
Metal coordination bonds can be coordinated to specific functional groups in polymers. This special coordination can give the material excellent self‐healing and mechanical properties. Nitrile rubber (XNBR)/CuCl 2 composites were prepared by solid‐state blending. By changing the coordination reaction temperature, different coordination bonds were formed between the nitrile rubber and copper ions. The starting temperature of the coordination reaction was determined to be 100°C by observing the changes in the coordination reaction curve. With the increase of temperature from 100°C to 190°C, the copper ions' oxidation state was raised to 3, while part of C ≡ N was transformed to C=N at high temperature. Quantitative analysis revealed that the linear coordination [Cu 2+ –N L ] was predominantly triple‐coordinated, and the curved coordination [Cu 3+ –N B ] was coordinated in the form of ionic clusters. In addition to this, the formation of linear coordination bonds was easier and more reversible based on the calculation of the apparent activation energy of the coordination reaction. Macroscopically, the mechanical properties and self‐repairing ability of XNBR/CuCl 2 ‐10‐100°C were higher than those of XNBR/CuCl 2 ‐10‐190°C. The design of cross‐linked XNBR with good mechanical properties and recycling performance was of great significance in protecting the environment and realizing sustainable development. Highlights: XNBR/CuCl 2 ‐10‐100°C composites mainly form linear coordination [Cu 2+ –3N L ]. XNBR/CuCl 2 ‐10‐190°C composites form bending coordination [Cu 3+ –NB]. [Cu 3+ –N B ] is stronger than [Cu 2+ –N L ] but less reversible.
Funding Information
  • Natural Science Foundation of Shandong Province (ZR2016AB07)

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