Fully Biobased High-Molecular-Weight Polyester with Impressive Elasticity, Thermo-Mechanical Properties, and Enzymatic Biodegradability: Replacing Terephthalate

The widespread utilization of petroleum-based plastics causes severe environmental and health issues, prompting the production of biobased high-performance polymers for a sustainable future. This work attempts to develop 100% eco-friendly polymers with comparable properties and the advantages of petro-based plastic, which may find useful applications in beverage packaging. A series of poly(alkylene sebacate-co-furanoate) copolyesters were synthesized using a two-stage melt polycondensation reaction utilizing biomass-derived substituents. Dimethyl furan 2,5-carboxylate and dimethyl sebacate, and different diols such as a 1,4-butane diol or 1,5-pentane diol were used for the synthesis of fully biobased polyester, namely poly(butylene sebacate-co-furanoate) (PBSF) and poly(pentylene sebacate-co-furanoate) (PPeSF). Solution viscosity, gel-permeation chromatography, FT-IR, and NMR spectroscopies confirm the formation of typical high-molecular-weight aliphatic-aromatic polyesters. The glycol chain length played a key role in forming high molecular weight polymers and affected the crystalline, rheological, and thermomechanical properties. Thermal investigations revealed a decrease in the melting and glass-to-rubber transition temperatures as well as a reduction in the crystallization capability with different glycol-chain lengths, a possible odd–even effect phenomenon. Compared to terephthalate-based copolyesters, furan-derived polyesters’ higher molecular weight, asymmetric, and nonplanar ring structure suffered significant chain entanglements, strengthening their elasticity, as validated by the rheological properties. Furthermore, biobased copolyester was successfully processed into films and characterized for mechanical, elastic recovery, and enzymatic degradation properties. From mechanical performance and enzymatic degradation studies, furan-derived polyester exhibited impressive elasticity upon stretching and good degradation capabilities compared to its terephthalate counterpart. PBSF exhibited remarkable extensibility with elongation of more than 600% and tensile strength of 8.4 MPa with an excellent recovery rate of 70% (to the original state) after stretching. These aliphatic-aromatic polyesters are biobased and can offer both mechanical and biodegradable alternatives to petroleum-based terephthalate counterparts or commercial polyester poly(butylene adipate-co-terephthalate).