Partially bio-based and tough polyesters, poly(ethylene 2,5-thiophenedicarboxylate-co-1,4-cyclohexanedimethylene 2,5-thiophenedicarboxylate)s

Novel tough bio-based polyesters poly(ethylene 2,5-thiophenedicarboxylate-co-1,4-cyclohexanedimethylene 2,5-thiophenedicarboxylate)s (PECTFs) were synthesized from 2,5-thiophenedicarboxylic acid (TDCA), 1,4-cyclohexanedimethanol (CHDM) and ethylene glycol (EG). The microstructure, thermal and mechanical properties were investigated. Poly(ethylene 2,5-thiophenedicarboxylate) (PETF) displayed the glass transition temperature (~64 °C) and tensile strength (~72 MPa) similar to poly(ethylene terephthalate) (PET). However, the nonlinear structure of TDCA resulted in an angle of 148° between carboxylic acid carbons and the S atom resulted in a permanent dipole, so the thiophene ring-flipping was hindered and the low elongation at break (~24%) was observed for PETF. The peak corresponding to the secondary relaxation shifted to lower temperature due to the incorporation of CHDM, which yielded ductile copolyesters with high elongation at break. When the CHDM content was equal to or higher than 29%, a high elongation at break (>160%) was observed.