Photo-oxidative Degradation and Biodegradation of Poly(ether-<i>block</i>-amide) Multiblock Copolymers

This study investigated the photo-oxidative degradation and biodegradation behavior of poly(ether-block-amide) (PEBA) multiblock copolymers with varying amide segments and polyethylene glycol (PEG) contents. The copolymer films were exposed to ultraviolet (UV) light in an artificial weathering machine to simulate the photo-oxidative degradation of these polymers in the environment. The biodegradation behavior of both the original and UV-exposed PEBA multiblock copolymer films was studied by immersing them in extracted seawater for 28 d. The degree of biodegradation was evaluated on the basis of the amount of carbon dioxide generated. The changes in the morphology, chemical structure, mechanical properties, molar mass, and microstructure of the PEBA multiblock copolymer films after UV exposure and biodegradation tests were investigated using laser microscopy, Fourier transform infrared spectroscopy, tensile testing, nanoindentation, size-exclusion chromatography, and wide-angle X-ray scattering. The PEBA multiblock copolymer with a higher PEG content exhibited faster photo-oxidative degradation under UV exposure, whereas the nylon-6-segmented PEBA multiblock copolymer demonstrated excellent biodegradability. Furthermore, the biodegradability of the PEBA multiblock copolymers significantly improved after UV exposure. The biodegradability of the PEBA multiblock copolymers was confirmed through field tests conducted in Ainan, Ehime, Japan. It was observed that a nylon-6-segmented PEBA multiblock copolymer containing 56 wt % PEG underwent complete degradation in the marine environment after six months. The findings of this study provide valuable insights into the design and optimization of biodegradable polymers to alleviate microplastic pollution in the environment.