Dynamically Cross‐Linked Semicrystalline Thiol–Ene Photopolymers for Additive Manufacturing of Recyclable and Adaptive Materials

Abstract Current photopolymers are mainly produced by (meth)acrylate‐based photoresins, possessing permanently cross‐linked structures that prohibit their chemical recycling. This study reports a one‐step, scalable synthesis of dynamically cross‐linked semicrystalline thiol–ene photopolymers comprising exchangeable disulfide bonds with excellent material performance, shape memory/adaptive characteristics, and chemical recyclability. These photopolymers are synthesized via stoichiometric thiol–ene click reactions using commercial reagents, including difunctional ene, alkyl dithiol giving rise to crystallinity, thiol‐terminated oligomer comprising dynamic disulfide bonds, and trithiol cross‐linker. Cross‐link density is systematically controlled by varying trithiol cross‐linker content to tune degrees of crystallinity and mechanical properties over a wide range, e.g., Young's modulus from 4 to 138 MPa, elongation‐at‐break from 40 to 370%, and toughness from 0.3 to 32 MJ m ⁻³ . Importantly, these dynamically cross‐linked photopolymers undergo complete decross‐linking via thiol‐disulfide exchange reactions with small‐molecule thiols at 120 °C in a solvent‐ and catalyst‐free manner, yielding liquid thiol‐terminated oligomers. These recycled thiol‐terminated oligomers are used to synthesize next‐generation dynamically cross‐linked thiol–ene photopolymers with identical material composition and full property retention, demonstrating closed‐loop recycling. Promisingly, these new thiol–ene photoresins demonstrate excellent feasibility for Digital Light Processing (DLP)‐based 3D printing of high‐resolution objects with complex geometries, preserved crystallinity and recyclability, and unique shape memory/adaptive characteristics.