Highly Reprocessable Diels–Alder Networks with Rapid Gelation for Enhanced Printability

Extrusion-based additive manufacturing of dynamic covalent polymer networks has faced longstanding challenges, preventing widespread adoption. Dynamic cross-linking via the thermoreversible Diels-Alder (DA) reaction has shown potential, however slow reaction rates resulting in poor viscosity control and thermal instability have posed significant constraints. Herein, we present a modular, scalable, solvent-free synthetic approach tailored to extrusion-based 3D printing. Linear oligomers densely functionalized with furan pendant groups are synthesized to accelerate postextrusion gelation. Through facile control of cross-linking density, networks with stiffnesses spanning from 2 to 200 MPa are obtained. Exceptional robustness to processing conditions is demonstrated via dynamic rheology, with networks undergoing 20 reprocessing cycles, marking a significant improvement for DA-based materials. Autonomous scratch healing at 20 °C is shown by a network combining high cross-linking density and chain mobility. Structures with mm-thin upright walls were printed using minimal or no support, marking an advancement in achievable features using purely dissociative DA-cross-linked networks, without viscosity-regulating additives. Fast gelation unlocks the trade-off between solidification rates and interlayer cross-linking, facilitating shape retention while mitigating mechanical anisotropy. The proposed approach establishes a pathway toward the scalable production of recyclable, tunable dynamic networks, providing a versatile platform for additive manufacturing, self-healing applications, and sustainable material development.