Computational and Experimental Study on the Mechanism of CO2 Production during Photo-Oxidative Degradation of Poly(butylene adipate-co-terephthalate): Differences between PBA and PBT Segments

As an important polymer in conventional applications, the service stability and biodegradability of poly(butylene adipate-co-terephthalate) (PBAT) have been well explored. However, the CO2 production mechanism during the photo-oxidation process remains unclear. Herein, CO2 production pathways in the photo-oxidative degradation of PBAT were investigated via calculations and experiments. A simulation strategy was established based on time-dependent density functional theory, and results show that ultraviolet (UV) radiation promotes the decarboxylation of poly(butylene terephthalate) under oxygen-free conditions, along with the oxidation and decomposition of poly(butylene adipate) segments under oxygen-rich conditions. Hole-electron analysis indicates that UV radiation alters the bonding states, lowering the energy barriers for the key reactions. In situ Fourier transform infrared spectroscopy and outdoor aging experiments substantiate the calculation results. Hence, this work sheds light on the photo-oxidative behavior of PBAT, enhancing our understanding of its application potential.