Fabrication of malleable, repairable, weldable, recyclable and robust epoxy vitrimers from itaconic acid for recycled adhesion

Epoxy vitrimers with robust mechanical properties, facile self-healing and recycling are highly desired and maintain a challenge. In the present work, a series of novel itaconic acid (IA) based epoxy vitrimers incorporated dynamic β-hydroxy ester bonds and boronic ester bonds were successful fabricated using IA derivate with double terminal epoxy and 2,2′-(1,4-phenylene)bis[5-methyl-1,3,2-dioxaborinane-5-carboxylic acid] (BDCB) with two carboxyl groups by a reaction between epoxy and carboxyl. The obtained IA-based epoxy vitrimer possesses comparable thermal stability (T5d = 255 °C) and mechanical properties (tensile strength = 68.3 MPa), elongation at break = 16.8 % and toughness = 6.43 MJ·m−3) to conventional epoxy resins, due to the rigid network frameworks. Meanwhile, the IA-based epoxy vitrimer show excellent self-healing, welding, physical reprocessing and chemical recycling due to the rearrangement of network typology by thermally-induced dioxaborolane metathesis and transesterification. The self-healing efficiency of the surface scratch reaches 100% at 150 °C for 2 h. High welding efficiency is observed as high as 84.2%. The mechanical properties of both the reprocessed and the chemical recycled IA-based epoxy vitrimers maintain 85.5% and 78.9% of the original one, respectively. The IA-based epoxy vitrimers can be applied in recycled adhesion with the adhesion strength of 16.2 MPa.