New biodegradable polyesters synthesized from 2,5-thiophenedicarboxylic acid with excellent gas barrier properties

Abstract

Lacking available eco-friendly aliphatic-aromatic copolyesters with balanced mechanical properties, gas barrier properties and biodegradability is a foremost challenge in the field of degradable materials. 2,5-thiophenedicarboxylic acid (2,5-TDCA) as a new aromatic monomer with five-membered aromatic-ring can be synthesized from the renewable glucaric or muconic acid. In this work, a series of poly(butylene succinate-co-butylene 2,5-thiophenedicarboxylate) (PBSTh) copolyesters with TDCA units ranging from 10 to 80 mol% were synthesized by melt polycondensation. The results of 1H-NMR, 13C-NMR and GPC revealed that the obtained random copolyesters possessed high number-average molecular weight from 54,800 to 88,600 g/mol. The copolymerized TDCA units was beneficial to improve the thermal stability, and Td,5% in N2 rose from 324°C of poly(butylene succinate) (PBS) to 344∼371°C of PBSThs. The mechanical properties of PBSThs were good with tensile modulus >29 MPa, tensile strength >11.4 MPa and elongation at break >523%, respectively. PBSThs showed better gas barrier properties than the well-known poly(butylene adipate-co-butylene terephthalate) (PBAT) and the BIFps of CO2 and O2 were 5.1∼60.2 times and 5.1∼32.0 times to PBAT, respectively. Also, the excellent biodegradability was proved both in enzymatic and compost environments and PBSThs have higher degradation rates than PBAT when the content of TDCA unit is lower than 60 mol%. In conclusion, the investigation of PBSThs has shown that the incorporation of 2,5-TDCA is effective in enhancing the overall properties of PBS and PBSTh can be a promising candidate in the field of biodegradable polymers.