Synthesis of recyclable polyesters via a <i>cis</i> -fused ring strategy

ABSTRACT The development of chemically recyclable polymers is critical for addressing the environmental and resource limitations of the traditional linear plastic economy. Owing to its intrinsic reversibility, ring-opening polymerization (ROP) offers great potential for the development of recyclable polymers. However, achieving a balance between monomer polymerizability, polymer performance and recyclability remains a key challenge. This study explores the design and synthesis of a novel cis-fused cyclobutane-butyrolactone monomer (C4GBL) for use in ROP, leading to the formation of a polymer with 1,2-cyclobutane units in the main chain. C4GBL was synthesized using ethylene and bio-based maleic anhydride, and the resultant polymer exhibits high thermal stability (Td,5% = 380°C). Thermodynamic analysis of the ROP of C4GBL revealed a ceiling temperature (Tc) of −24°C, indicating that both polymerization and chemical recycling are feasible under appropriately tuned conditions. Density functional theory optimization reveals that the rigid fused cyclobutane forces the lactone segment of C4GBL into a near-eclipsed conformation, enhancing ring strain and polymerization reactivity. Collectively, this work establishes the cis-fused ring strategy as a new design principle for recyclable polyesters.