High Glass Transition Temperature Copolyesters from Biobased 2,5-Thiophenedicarboxylic Acid with Excellent Mechanical Properties

Thermally resistant polymers are extensively used in packaging, electronic products, and automobiles, while synthesizing high glass transition temperature polymers from biomass remains challenging. Herein, a series of biobased poly(cyclohexanedimethylene-<i>co</i>-2,2,4,4-tetramethyl-1,3-cyclobutylene thiophenedicarboxylate) (PCBTh) copolyesters were synthesized via a conventional two-step melt polycondensation method using biobased 2,5-thiophenedicarboxylic acid. The comprehensive properties of PCBTh copolyesters, including thermal resistance, thermal stability, mechanical properties, gas barrier properties, and optical transparency, were systematically investigated. With the incorporation of rigid 2,2,4,4-tetramethyl-1,3-cyclobutanediol up to 50 mol % into the molecular chains, the glass transition temperature of PCBTh copolyesters was synergistically enhanced from 71.4 to 102.5 °C. Meanwhile, the tensile modulus and tensile strength increased to 1650 and 53 MPa, respectively, with an elongation at break of 38%. These results demonstrate that PCBTh copolyesters are promising biobased materials for high thermal resistance packaging applications.