New bio-based copolyesters derived from 1,4-butanediol, terephthalic acid and 2,5-thiophenedicarboxylic acid: Synthesis, crystallization behavior, thermal and mechanical properties

A series of 2,5-thiophenedicarboxylic acid-based copolyesters (PBTTFs) were synthesized from 2,5-thiophenedicarboxylic acid (TFDCA), terephthalic acid (TA) and 1,4-butanediol (BDO). A straight forward partial substitution of non-renewable TA by renewable TFDCA was successfully done. The effects of composition on microstructure, crystallization behavior, thermal properties, and mechanical properties were investigated. When the content of TFDCA varied from 0 to 25%, the elongation at break varied from 9.1% to 348%. When the content of TFDCA was 75%, the tensile strength was 39.3 MPa and the elongation at break was 1223%. In summary, TFDCA can toughen poly(butylene terephthalate) (PBT) to the extent. For PBTTF25, PBTTF50, PBTTF75 and PBTTF87.5, the isodimorphic cocrystallization was observed. Additionally, DSC and WAXD results suggested the butylene terephthalate (BT) unit had the stronger crystallization ability compared to the butylene 2,5-thiophenedicarboxylate (BTF) unit.