Tunable Thermal-Induced Degradation in Fully Bio-Based Copolyesters with Enhanced Mechanical and Water Barrier Properties

Bio-based fumaric acid act as a key monomer for the fabrication of high-performance and thermal-induced degradation polymers. Obtained poly(butylene 2,5-furandicarboxylate/fumarate) copolyesters had a high number-average molecular weight from 27,500 to 37,600 g/mol. Trans C═C bonds and the conjugated effect provide interesting properties. Influenced by the thermal history, the elastic modulus and tensile strength (>50 MPa) are much higher than PBAT. Trans C═C bonds of fumaric acid and intermolecular interactions of furan rings restrict the diffusion of gas and water molecules. Specifically, the water barrier is 4–12 times better than PBAT, filling the gap in biodegradable food packaging. The hydrolysis resistance of fumarate segments provides good durability during their life span. The functionalization of PBFFu by thiol-Michael addition was performed at room temperature. Three substituent groups bring different conditions of pendant amino groups, resulting in the thermal-induced intramolecular cyclization from 40 to 100 °C. Fumaric acid could be a critical point to achieve the coordination of high-performance and temperature-induced degradation.