Mechanically Robust and Depolymerizable Polyesters With Near‐Complete Monomer Recovery for Circular Additive Manufacturing

Designing polymers that combine tunable macromolecular architecture with complete chemical recyclability remains a fundamental challenge in sustainable polymer chemistry. Here, we report a δ-lactone copolymer platform synthesized via controlled ring-opening polymerization of δ-dodecalactone (δ7) and δ-valerolactone (δ0), enabling regulation of molecular architecture, mechanical response, and depolymerization pathways within a single polyester chemistry suitable for additive manufacturing (AM; or 3D printing). Segmental programming of δ7 and δ0 domains yields a synergistic combination of chain mobility and reversible crystalline reinforcement, producing recyclable, high-stiffness 3D-printing precursors with elastic modulus elevated by 2-3 orders of magnitude relative to prior δ-lactone materials. End-group functionalization generates methacrylate-terminated copolymers and acrylate-terminated macromonomers that undergo efficient photopolymerization without disrupting the depolymerizable backbone. Blending these components produces photocurable formulations with rheology governed by intrinsic polymer design, enabling compatibility with direct ink writing and digital light processing via temperature-mediated control of segmental crystallinity. This strategy eliminates external monomers or permanent crosslinkers, preserving chemical integrity and recyclability. Increasing molecular weight shifts the system into an entanglement-dominated thermoplastic regime for fused filament fabrication. Sequential thermal-catalytic unzipping exploits ceiling-temperature differences to recover δ7 and δ0 monomers with ∼95% efficiency even from crosslinked networks, with repolymerization yielding materials indistinguishable from virgin polymers.