Daan S. van Es

Films of poly(ethylene furanoate) (PEF) and poly(neopentyl furanoate) (PNF) of different molecular weights were artificially weathered in a Q‐SUN test chamber for up to 500 h. The chemical and physical changes of the films have been evaluated with a wide range of techniques. All films, independent of molecular weight or crystallinity, show evidence of partial cross‐linking and the formation of new carbonyl species. Furthermore, all irradiated films show changes in thermal properties and crystallization behavior. The extent of degradation was higher for the amorphous films as compared to their semi‐crystalline counterparts, suggesting that UV degradation predominantly occurs in the amorphous phase. The apparent higher UV‐sensitivity of PNF, as compared to PEF, suggests that the nature of the diol, and the resulting polymer properties, affects the UV‐stability of the polymer. Nevertheless, comparison with poly(ethylene terephthalate) (PET) shows that the different electronic structure and properties of the furan ring are the most likely cause of the observed UV‐instability.