Toughness refers to the ability of a material to absorb energy during plastic deformation and fracture. Material strength and toughness are two important mechanical properties. Plastic toughening has always been an important topic in the scientific research of polymer materials, but in general, toughening and strengthening are often contradictory. The toughness and impact properties of polymer are improved, but the strength and stiffness of the materials are reduced; In reinforced plastics, it usually leads to the reduction of toughness and impact strength. Therefore, how to obtain polymer materials with excellent comprehensive properties, which are both reinforced and toughened, is a big challenge in the scientific research of polymer materials.
At present, the introduction of dynamic chemical bonds into polymer materials is an effective method to improve their toughness. Because these dynamic bonds (reversible covalent bond or non covalent weak interaction, etc.) are relatively weak, they will first break and dissipate energy under external force. At the same time, they can quickly re-form so that the material will not be completely destroyed. Therefore, they can significantly improve the toughness while maintaining high strength. The structures of metal complex are changeable and dependent on the molar ration of ligands and metal ions with variable coordination numbers. Therefore, the fracture of local coordination bond will not destroy the structure of the complex as a whole. The fracture of coordination bond makes the energy dissipate in time. Therefore, the introduction of coordination bonds into polymers can effectively improve the toughness of materials.
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