Bio‐Based Aliphatic‐Aromatic Random Copolyesters Derived From 2,5‐Furandicarboxylic Acid: From Crystalline Thermoplastics to High‐Elongation Flexible Plastics

ABSTRACT 2,5‐Furandicarboxylic acid (FDCA), as a key bio‐based platform compound, represents an ideal alternative to terephthalic acid (TPA). This study aims to improve the toughness of PNF through copolymerization modification. To the best of our knowledge, FDCA, NPG, and aliphatic glutaric acid (GA) were employed as monomers for the first time to synthesize a series of novel bio‐based random copolyesters—poly(neopentylene glutarate‐co‐neopentylene furanoate) (PNGF)—via melt polycondensation, with GA molar fractions ranging from 0% to 53%. The structure and properties of the copolyesters were systematically characterized by 1 H NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD). The results demonstrate that PNGF forms random copolymers with compositions precisely controllable by the monomer feed ratios. With increasing GA unit content, the glass transition temperature ( T g ) of the copolyesters gradually decreased, and the melting point ( T m ) and cold crystallization temperature ( T cc ) of the crystallizable samples (PNGF40–PNF) shifted to lower temperatures as well, while excellent thermal stability was maintained ( T dmax > 400°C). Mechanical testing revealed a transition in material behavior from rigid thermoplastics (high PNF content) to flexible, highly stretchable plastics (high GA‐unit content), with the maximum elongation at break reaching 917% (PNGF20) and the maximum Young's modulus reaching 1963 MPa (PNGF45).