Comparable Investigation on Enhancing Poly(butylene furandicarboxylate) Performance with Sustainable Citric Acid-Derived Monomers

Structural modulation is essential for the advancement and broader application of high-performance biobased polyesters. In this study, two series of PBF-based copolyesters, PB x O y F and PBO x F y, were synthesized by reacting citric acid-derived octahydro-2,5-pentalene diol (OPD) and octahydro-2,5-pentalenediol bis(methyl carbonate) (OPBMC) with 2,5-dimethylfuran dicarboxylate and 1,4-butanediol. These copolyesters exhibited a random microstructure and viscosity average molecular weights ( M η ) between 27.7 and 48.6 × 10 3 g/mol. The characteristics of copolyesters were closely linked to their composition and the types of substituent units. As the citric acid unit content increases, the thermal stability of the copolyesters decreases but remains adequate up to 300 °C. Concurrently, their crystallinity diminishes, primarily as a result of the incorporation of OPBMC units. The glass transition temperature ( T g ) of PBF significantly elevated with the addition of both OPD and OPBMC units, with OPD showing a stronger effect. The incorporation of rigid OPBMC units into PBF chains improved elongation at break, elastic modulus, and tensile strength, whereas an increase in OPD units resulted in increased brittleness and reduced mechanical properties. PBF-based copolymers incorporating citric acid units exhibit high T g, tunable properties, and sustainability, making them promising candidates for eco-friendly packaging materials.