Enhanced degradability of novel PBATCL copolyester: Study on the performance in different environment and exploration of mechanism

Abstract

To enhance the biodegradability of poly (butyleneadipate-co-terephthalate) (PBAT), ε-caprolactone (ε-CL) was introduced as a fourth monomer, resulting in poly (butyleneadipate/terephthalate-co-caprolactone) (PBATCL) with different adipic acid/terephthalic acid (A/T) ratios and CL contents. These polyesters maintained superior thermal stability and improved hydrophilicity compared to PBAT. Samples were placed under artificial conditions, including non-enzymatic and enzyme-containing phosphate-buffered saline, and two natural soil and oceanic environments for 180 days to investigate the material’s degradation behaviors. PBATCL exhibited poor non-enzymatic hydrolysis similar to that of PBAT, but dramatically improved degradability in the presence of enzymes and microorganisms. Therefore, the material can be quickly degraded in natural environment by adjusting the composition ratio. The degradation mechanism was further investigated from a chemical structure perspective via the two dimensions of water-soluble intermediates and the residual matrix, and we found that the content of adipic acid (AA) and CL contributed to degradability. The ester bond formed by AA and CL is susceptible to hydrolysis, while the CL introduction also promotes the ester bond reactivity between the aromatic segments. Furthermore, Cell Counting Kit-8 (CCK-8) experiments showed that the degradation products were non-toxic and harmless to organisms. These results lay the foundation for designing targeted biodegradable polymers and provide a reference for understanding thedegradation mechanism of such materials.