Stereochemical Regulation in Furan-Based Polyesters: Achieving High T g and Excellent Ductility via Synergistic Cyclic Ring Modification

Abstract Developing biobased polyesters as sustainable alternatives to petroleum-based counterparts is urgently needed, yet furan-based polyesters often suffer from intrinsic brittleness. Conventional toughening strategies typically compromise heat resistance, creating a persistent trade-off. To overcome this challenge, we designed a series of furan-based copolyesters poly(ethylene-co-cyclohexanedimethylene-co-2,2,4,4-tetramethylcyclobutane-1,3-diyl furandicarboxylate) (PECTF) by incorporating two rigid cyclic diols, 1,4-cyclohexanedimethanol (CHDM) and 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), and crucially regulated the stereochemistry of CHDM by systematically increasing its trans-isomer content. The high structural regularity imparted by the trans-isomer, combined with the intrinsic rigidity of CBDO, effectively suppresses macroscopic segmental motion while preserving localized flexibility via conformational transitions. As a result, the optimized copolyester PECT35F-90 achieves an exceptional balance of properties, including a high glass transition temperature of 101.7 °C, a tensile strength of 33.8 MPa, an elongation at break of nearly 30%, and a moderate toughness of 12.65 MJ·m–3. Moreover, the resulting films exhibit superior optical transparency, highly efficient UV-shielding capability, and strong resistance to common organic solvents. In vitro cytotoxicity and hemolysis assays further confirm excellent biocompatibility. This stereochemical regulation strategy offers a robust pathway toward high-thermal-resistant and tough sustainable polyesters for advanced packaging applications.