Toward Sustainable FDCA-Based Copolyesters: Integrating High Performance and Closed-Loop Recyclability through Camphoric Acid-Derived Structural Modulation

Chemical recovery at the end-of-life while meeting stringent performance specifications remains a prominent challenge in the development of bio-based polyesters. Here, fully bio-based poly(butylene-co-trimethylcyclopentane-1,3-dimethylene furandicarboxylate) (PBTCF) copolyesters were synthesized from dimethyl 2,5-furandicarboxylate, 1,4-butanediol, and a rigid camphoric acid-derived cyclic diol (TCDM) via two-step melt transesterification-polycondensation. TCDM incorporation restricted segmental mobility, increasing the glass transition temperature from 38.4 to 64.3 °C while improving optical transparency and solvent resistance. PBTCF3 (3 mol % TCDM) combined a tensile strength of 55 MPa with 500% elongation at break. Furthermore, rapid depolymerization in THF/BDO/NaOH under mild conditions yielded FDCA (85.7% recovery; 99.1% purity) and BDO (97.8% purity). Recovered FDCA was converted to DMFD, which was then repolymerized with recovered BDO and fresh TCDM to produce a polyester comparable to the original in molecular weight, thermal properties, and mechanical properties. This work presents a viable approach to harmonizing high performance with sustainability in bio-based polymers.