Photooxidation-induced conformational changes and degradation behaviors of poly(butylene succinate) and poly(butylene succinate-co-adipate)

Two biodegradable polyesters, poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA), were artificially aged in a UV irradiation test chamber, and their photodegradation behaviors investigated. The attenuated total reflection (ATR) infrared (IR) spectra of the initial and UV-aged samples revealed conformational changes in the tetramethylene sequences of the photoaged PBS and PBSA. The one-dimensional wide-angle X-ray scattering (WAXS) profiles showed that the (110) d-spacing of the alpha-form crystal progressively decreased during UV aging, suggesting that the crystalline polymer chains became arranged more closely along the fiber axis. Accordingly, we conclude that PBS and PBSA transform from their TGTGT to nearly TTTTT conformations upon photoaging. The observed WAXS, small-angle X-ray scattering, and IR spectral data suggest that photodegradation preferentially occurs in the amorphous phase of each polymer. The less crystallizable butylene adipate co-unit enhances the degradability of PBSA, with prolonged photooxidation leading to partial degradation of the crystalline region of the copolymer. This finding is consistent with and may be linked to the higher biodegradability of PBSA compared to PBS.