Biobased Amorphous Polyesters with High Tg: Trade-Off between Rigid and Flexible Cyclic Diols

Almost all biobased polyesters are semicrystalline polymers with relatively low glass transition temperature (Tg). Amorphous polyesters derived from renewable resources with Tg higher than 100 °C are highly desired. In this work, both rigid (2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO)) and flexible (1,4-cyclohexanedimethanol (CHDM)) cyclic diols were polymerized with 2,5-furandicarboxylic acid (FDCA), leading to copolyesters (PECTFs) showing a Tg range 80.3–105.7 °C. Results showed that CBDO units contributed positively to high Tg, and the presence of CHDM could increase the molecular weight. When the content of CBDO units was 45%, PECTF-45 showed a Tg of 103.1 °C, tensile strength of 88 MPa, and tensile modulus of 2140 MPa. In addition, the transparency by cutoff at 700 nm for PECTF-45 was 89.8%, and it showed better solvent resistance compared to polycarbonate (PC). The biobased polyesters demonstrating a satisfying performance were reported in this work.