Effect of Coordination Sacrificial Bond Strength on Toughening Properties of Polyesters

By the coordination of dangling terpyridine (TPY) ligands with transition metal ions to form supramolecular cross-linking points as sacrificial bonds (SBs), a double-cross-linked system is constructed from the physically cross-linked semicrystalline polyesters. The mechanical properties are greatly enhanced, and the effect of coordination interaction strength on the toughening effect has been investigated by using different ions (Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺). It shows that stronger coordination bonds provide a larger Young’s modulus, but not for strength and toughness, which increase first and then decrease after achieving a maximum value at an optimal SB strength. This is due to the properties estimated at different strains, where the supramolecular and physically cross-linking points behave differently. Our results demonstrate that SB strength is not the higher, the better, which should be useful for the design of strong and tough materials.