Mechanochemical H‐Bonding Organocatalysis Enabled Controlled Synthesis and Recycling of High‐Molecular‐Weight Poly(ɛ‐Caprolactone)

ABSTRACT The use of organocatalysts for the ring‐opening polymerization (ROP) to achieve high‐molecular‐weight poly(ε‐caprolactone) (PCL) remains challenging. In this study, we present a mechanochemical hydrogen‐bond‐catalyzed ROP (mechano‐HROP) strategy. This approach combines a tris‐urea/base co‐catalysis together with ball milling to achieve rapid and controlled solid‐state polymerization of ɛ‐caprolactone (ɛ‐CL) at room temperature. The mechano‐HROP demonstrated exceptional polymerization activity ( k obs = 0.053 min −1 ) while suppressing transesterification reactions compared to conventional bulk ROP. This method enabled the complete conversion of monomers into high‐molecular‐weight PCLs with M n up to 185.0 kDa and narrow distribution ( Ð < 1.28). The PCL synthesized via mechano‐HROP exhibited high chain‐end fidelity, as evidenced by MALDI‐TOF analysis and successful chain extension from its active chain ends. Density functional theory calculations confirmed the presence of an intramolecular hydrogen‐bonding self‐activated imidate species under solvent‐free condition. Furthermore, we introduced a mechanochemical methanolysis method for PCL recycling under solvent‐free and room temperature conditions. Kinetic comparisons with stirred methanolysis highlight the efficiency of mechanochemistry in PCL depolymerization. In summary, this work establishes a highly efficient mechanochemical route for the synthesis and recycling of high‐molecular‐weight PCLs.