Shape reconfiguration and functional self-healing of thermadapt shape memory epoxy vitrimers by exchange reaction of disulfide bonds

Abstract

Epoxy-based shape memory materials still face many challenges from preparation to application. Designing dynamic covalent bonds into the cross-linked network of epoxy can bring many new properties to them, which is expected to solve some of the problems faced. In this paper, epoxy vitrimers with different contents of exchangeable disulfide bonds were synthesized by the polymerization of hydrogenated epoxy resins with diacids containing dynamic disulfide bonds. The effect of disulfide bond content on the properties of epoxy vitrimers was systematically studied. By activating the exchange reaction of disulfide bonds, the permanent shape of epoxy vitrimers can be reconfigured, even from two to three dimensions. The time required for reconfiguring is affected by the content of disulfide bonds, the more disulfide bonds, the shorter the time required. The epoxy vitrimers with more content of disulfide bonds were found to have lower recovery ratio loss after the same shape memory cycle by thermal bending experiments. More importantly, the epoxy vitrimers with more content of disulfide bonds also exhibited better functional self-healing properties. The decreased recovery ratio can be healed by periodic heat treatment, thus ensuring that the epoxy vitrimers perform more shape memory cycles and maintain a high shape recovery ratio. These experimental results will serve as a basis for expanding the range of applications and prolonging the service life of epoxy-based shape memory materials.