High thermal resistance biobased copolyester from 2,5-Thiophenedicarboxylic acid with excellent gas barrier properties

Driven by sustainable development strategies, bio-based polyesters have received significant attention due to renewable bio-derived monomers and various unique properties. In this study, a series of high molecular weight bio-based poly(ethylene- co -2,2,4,4-tetramethyl-1,3-cyclobutylene thiophenedicarboxylate) (PETTh) copolyesters on the basis of an emerging bio-derived aromatic diacid, 2,5-thiophenedicarboxylic acid (TDCA), was synthesized by a conventional two-step melt polycondensation method. Copolymers were random copolyesters with weight-average molecular weights ( M w ) in the range from 65,400 to 84,100 g/mol. Their comprehensive properties, including thermal transition properties, thermal stability, mechanical properties, gas barrier properties, as well as optical transparency were systematically investigated. Rigid 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) cyclic diol contributed a positive effect to thermal resistance, leading to the glass transition temperature ( T g ) growing from 65.3 °C of PETh to 85.3 °C of PET 42 Th. Furthermore, the mechanical properties, gas barrier properties and optical transparency were improved as diol segment was incorporated. Especially, all copolyesters displayed great ductility with elongation at break between 54 and 195 %. Meanwhile, the gas barrier properties of copolyesters were 3.9-fold to 16.3-fold for CO 2 and 3.0-fold to 6.0-fold for O 2 better than PET. Therefore, PETTh copolyesters might potentially substitute for commercial PET and they are extremely suitable for food packaging materials.