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

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-thiophenedicar-boxylic 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-thio-phenedicarboxylate) (PBSTh) copolyesters with TDCA units ranging from 10 to 80 mol% were synthesized by melt polycondensation. The results of H-1-NMR, C-13-NMR and GPC revealed that the obtained random copo-lyesters 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 T-d,T-5% in N-2 rose from 324 degrees C of poly(butylene succinate) (PBS) to 344 similar to 371 degrees 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 O-2 were 5.1 similar to 60.2 times and 5.1 similar to 32.0 times to PBAT, respectively. Also, the excellent biodegrad-ability 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.