Poly(ethylene 2,5-thiophenedicarboxylate-co-2,5-furandicarboxylate) copolyesters with improved ductility and PEF-comparable high performance

Poly(ethylene 2,5-furandicarboxylate) (PEF) is an important biobased polyester with not only high glass transition temperature (Tg), excellent strength and rigidity but also superior gas barrier properties. However, its poor ductility could limit its applications. In this study, 2,5-thiophenedicarboylic acid (TDCA) was used to modify PEF by copolycondensation. By introducing 10–40 mol% TDCA, poly(ethylene 2,5-thiophenedicarboxylate-co-2,5-furandicarboxylate) (PEThF) copolyesters with intrinsic viscosity of 0.63–0.77 dL/g were synthesized and characterized with 1H NMR, DSC, TGA, etc. The copolyesters are all amorphous polymers. Brittle-ductile transition was observed during tensile testing of PETh10F (PEThF containing 10 mol% 2,5-thiophenedicarboxylate unit). PEThFs containing 20–30% 2,5-thiophenedicarboxylate unit showed not only clearly improved ductility but also well-maintained performance advantages of PEF including high Tg (84–81 °C), modulus (∼3.2 GPa), strength (yielding 95 MPa, breaking 60 MPa) and oxygen barrier (5.4–5.0 times PET).