High barrier polyesters based on 2,5-furandicarboxylic acid and disulfide bond: Smart degradation induced by low concentrations of redox reagent

Abstract

Bio-based and biodegradable polymers opens up opportunities to overcome resource depletion and plastic pollution. However, the degradation mechanism based on ester bond breakage makes it difficult to achieve controllable degradation induced by external stimuli. In this work, we present a new 2,5-furandicarboxylic acid-based copolyesters (PBFDi) by partially replacing carbon–carbon backbones with disulfide bonds and discuss the influence of disulfide bonds on thermal stability, crystallization behavior, mechanical and barrier properties of polyesters. They could maintain stable for 1 h at processing temperatures of 220 °C, meeting the needs of long-term melt processing. The asymmetric structure of the furan ring and the slower free rotation of disulfide bonds help restrict the mobility of chains and obstruct gas permeation, resulting in 9.3–126.7 times increase in O2 barrier than commercial PBAT. With the introduction of small amount (≤40 %) of disulfide bond units, the hydrolysis rate is relatively slow and can maintain stable during storage and use. As expected, the copolyesters show redox dual-responsive degradation. Even at low concentrations (0.01 M and 0.1 M) of H2O2, the transition from hydrophobicity to hydrophilicity can be achieved, expected to accelerate the hydrolysis of PBFDi. The fast cleavage of disulfide bonds induced by DTT could be influenced by the copolymerized FDCA units. Lastly, the redox dual-responsive mechanism is elucidated, and how the rigid FDCA co-monomers affect the redox dual responsiveness is also clarified.