Vitrimer chemistry for 4D printing formulation

Vitrimerization is one of the new methods under development to convert polymer wastes into high-value compounds. The chemistry of vitrimers is such that the presence of dynamic chemical bonds changes the permanent covalent bonds into covalent adaptable networks, which are reversible. This allows for recycling and reprocessing of polymers by maintaining their initial properties after several cycles, which is included in the preparation of polymer resins to convert polymer waste into materials that can be formulated for three-dimensional (3D) printing resins. Four-dimensional (4D) printing has also been recently introduced as sustainable 3D printing of responsive polymers with dynamic applications, such as soft robotics, medicine, and medicals. Therefore, the synthesis of polymers with dynamic chemistry based on vitrimers can add unique properties such as shape memory, shape recovery, self-healing, and flexibility to the 3D printed products. Vitrimerization chemistry could contribute to polymer waste by producing 4D-printed resins. This article presents the vitrimerization chemistry used in different polymers to produce 4D printing resins with the mentioned capabilities and lists their recipes for the preparation of formulations used in 4D printing so that the researchers can use them in a practical way to possibly achieve simultaneous shape-programmable, self-healing, and recyclable features in printed structures.