DLP 3D printing of high-performance thermosetting polymers with photothermal dual-curing resin containing reversible covalent bonds

The utilization of photopolymers as structural materials remains challenging, primarily due to their inadequate mechanical properties arising from insufficient curing degree. Photothermal dual-curing strategy can enhance the mechanical properties; however, they still face significant challenges including storage stability and internal stress-induced cracking during the thermal curing process. In this study, a polyurethane acrylate containing reversible pyrrolidone urea bonds was constructed and then blended with epoxy resin to fabricate a novel hybrid resin for DLP 3D printing technology. The hybrid resin achieved precise printing via photopolymerization of acrylates in the first UV curing stage, while the dynamic bonds dissociated and in-situ triggered the curing of epoxy resin in the second thermal curing stage, significantly enhancing the mechanical properties. This design ensured the storage stability of the hybrid resin, attributed to the high dissociation temperature of the dynamic bonds, while dissipated internal stress through flexible chain segments in polyurethane, effectively avoiding cracking risks. More crucially, the hybrid resin formed a uniform single-network structure through photothermal dual-curing mechanism and dynamic exchange reaction, thereby imparting superior mechanical properties and thermal resistance. The alternating rigid-flexible molecular structure endowed the material with excellent shape memory performance. This work presents a novel strategy for developing stable, low-stress and high-performance photopolymer resins for UV curing-based 3D printing. • A novel photo-thermal dual-curing DLP resin is constructed with polyurethane acrylate and epoxy. • The polyurethane acrylate contains dynamic pyrrolidone urea bonds. • The hybrid resin achieves precise 3D printing via photopolymerization of acrylates. • The dynamic bonds dissociate in the thermal curing stage and in-situ trigger the curing of epoxy resin. • The printed objects exhibit superior mechanical properties and excellent shape memory performance.