Controlling the Mechanical Properties of Catalyst-Free Epoxy Vitrimers via Designing Molecular Networks

In this work, different fractions of poly(sebacic acid anhydride) (PSA) are used to control the molecular networks of epoxy vitrimers synthesized from diglycidyl ether of bisphenol A (DGEBA) and glutaric anhydride (GA) under the initiation of 1,4-benzenedimethanol (BDM). It is found that the toughness and self-healing performance of the modified epoxy vitrimer are significantly improved by the introduction of PSA with a long alkyl chain. Particularly, with the addition of 10 wt % PSA, the impact toughness and elongation at break of the epoxy vitrimer are increased by 1966.2 and 855.2%, respectively; meanwhile, the self-healing and reprocessing performances are improved. Furthermore, relative mechanisms are proposed in terms of the reaction of PSA with a long alkyl chain in the molecular network structure. Specifically, under the initiation of the hydroxyls of BDM, not only carboxyl groups can be formed via the ring-opening of GA but also sebacic acid (SA) can be formed via the reaction of the anhydride of PSA, so that abundant dicarboxylic acids can react with the epoxide groups of DGEBA, and thus PSA with a long alkyl chain can be introduced into the molecular networks of the epoxy vitrimer. As a result, the transesterification and the relaxation of the molecular networks are advanced, and the toughness is significantly improved. This work supplies a simple method to prepare toughened catalyst-free epoxy vitrimers with self-healing and reprocessing properties.