Synthesis and Properties Investigation of Thiophene-aromatic Polyesters: Potential Alternatives for the 2,5-Furandicarboxylic Acid-based Ones

In order to explore new substitutes for 2,5-furandicarboxylic acid (FDCA) or poly(ethylene 2,5-furandicarboxylate) (PEF) and try to develop more ideal bio-based polyesters, several thiophene-aromatic polyesters (PETH, PPTH, PBTH, and PHTH) were synthesized from dimethyl thiophene-2,5-dicarboxylate (DMTD) and different diols, including ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol. The chemical structures of obtained polyesters were confirmed by nuclear magnetic resonance spectroscopy ( 1 H-NMR and 13 C-NMR). Determined by GPC measurement, their average molecular weight ( M w ) varied from 5.22 × 10 4 g/mol to 7.94 × 10 4 g/mol with the molar-mass dispersity of 1.50–2.00. Based on the DSC and TGA results, the synthesized polyesters PETH, PPTH, and PBTH displayed comparable or even better thermal properties when compared with their FDCA-based analogues. From PETH to PHTH, their T g varied from 64.6 °C to −1 ×C while T 5% ranged from 409 °C to 380 °C in nitrogen atmosphere. PETH showed elongation at break as high as 378%, tensile strength of 67 MPa, and tensile modulus of 1800 MPa. Meanwhile, the CO 2 and O 2 barrier of PETH was 12.0 and 6.6 folds higher than those of PET, respectively, and similar to those of PEF. Considering the overall properties, the synthesized thiophene-aromatic polyesters, especially PETH, showed great potential to be used as an excellent bio-based packaging material in the future.