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 ( T g ), 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 1 H NMR, DSC, TGA, etc . The copolyesters are all amorphous polymers. Brittle-ductile transition was observed during tensile testing of PETh 10 F (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 T g (84–81 °C), modulus (∼3.2 GPa), strength (yielding 95 MPa, breaking 60 MPa) and oxygen barrier (5.4–5.0 times PET).