High Molecular Weight Poly(butylene succinate-co-butylene furandicarboxylate) Copolyesters: From Catalyzed Polycondensation Reaction to Thermomechanical Properties

Novel potentially biobased aliphatic-aromatic copolyesters poly(butylene succinate-co-butylene furandicarboxylate) (PBSFs) in full composition range were successfully synthesized from 2,5-furandicarboxylic acid (FA), succinic acid (SA), and 1,4-butanediol (BDO) via an esterification and polycondensation process using tetrabutyl titanate (TBT) or TBT/La(acac)(3) as catalyst. The copolyesters were characterized by size exclusion chromatography (SEC), Fourier transform infrared (FTIR), H-1 NMR, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and their tensile properties were also evaluated. The weight average molecular weight (M-w) ranges from 39 000 to 89 000 g/mol. The copolyesters are random copolymers whose composition is well controlled by the feed ratio of the diacid monomers. PBSFs have excellent thermal stability. The glass transition temperature (T-g) increases continuously with phi(BF) and agrees well with the Fox equation. The crystallizability and T-m decrease with increasing butylene furandicarboxylate (BF) unit content (phi(BF)) from 0 to 40 mol %, but rise again at phi(BF) of 50-100 mol %. Consequently, the tensile modulus and strength decrease, and the elongation at break increases with phi(BF) in the range of 0-40 mol %. At higher phi(BF), the modulus and strength increase and the ultimate elongation decreases. Thus, depending on phi(BF), the structure and properties of PBSFs can be tuned ranging from crystalline polymers possessing good tensile modulus (360-1800 MPa) and strength (20-35 MPa) to nearly amorphous polymer of low T-g and high elongation (similar to 600%), and therefore they may find applications in thermoplastics as well as elastomers or impact modifiers.