Rapid self-healed vitrimers via tailored hydroxyl esters and disulfide bonds

Conventional epoxy vitrimer containing single type of dynamic covalent bonds constitutes a class of polymer materials that integrates the advantages of thermoplastics and thermosets. However, the response of single type of dynamic covalent bond is slow, so it is very meaningful to combine multiple dynamic covalent bonds with adjustable proportions into one network for endowing vitrimers with diversified properties, especially rapid self-healing performances. Based on this consideration, we designed a series of epoxy vitrimers containing β-hydroxyl esters and disulfide bonds with adjusting any proportions. To this end, carboxylic acid-extended epoxy resins containing dynamical β-hydroxyl esters were first prepared through chemical reactions between conventional epoxy resin and suberic acid (SA), and then cured by aromatic disulfides (SS) to form vitrimers containing β-hydroxyl esters and disulfide bonds. Here, the SA part offers soft segments and dynamic β-hydroxyl esters, the curing agent SS part supplies hard segments and dynamic disulfide bonds. The properties of vitrimers with dual dynamic bonds are easily tailored by changing the ratio of SA and SS. Vitrimers with dual dynamic bonds exhibit excellent rapid self-healing properties closing to 80% after healing only 10 min, and the theoretical healing efficiencies are in good agreement with the actual values.