Repairable 3D printable photopolymer resins based on low-activation-energy adaptable covalent bonding

The rapid increase in the consumption of photoinitiated 3D printing materials requires sustainable and competitive new materials. This study demonstrated that covalently adaptable acrylate and methacrylate photopolymer-based resins can print objects with high resolution but maintain their repairability after printing by catalyzed transesterification reactions at high temperatures. A simple and elegant but high-yield approach was employed to effectively synthesize dihydroxypropyl methacrylate (DHPMA) monomers from glycidyl methacrylate. This resin is an ideal component in photoresin formulations for vitrimer 3D printing due to its low viscosity and high hydroxyl group content. Methacrylate phosphate (MAPs) and glycerol 1,3-diglycerolate diacrylate (GDGDA) were introduced as new transesterification catalyst and crosslinker, respectively. A series of methacrylate-based vitrimers with easily adjustable mechanical properties were developed using an appropriate design. 3D complex objects were obtained via bottom-up digital light processing (DLP) with feature sizes of approximately 50 mu m. The low activation energy (Ea) of the covalent crosslinks results in an intensive bond exchange reaction at high temperature, which provides the printed structures with thermoactivated repairability up to 95 % of the initial strength following the first healing process. The developed materials offer a potential way for a closed-loop economy of plastic.