New insights into the mechanism of photodegradation of chitosan

Chitosan films were subjected to accelerated artificial weathering at lambda >300 nm and 60 degrees C in the presence of O-2. The resulting variations in the chemical structure were characterized by IR spectroscopy and UV-vis spectroscopy, and a photooxidation mechanism was proposed based on the identified oxidation photoproducts. The formation of gluconolactone derivatives leading to chain scissions was shown. In addition, low molecular weight photoproducts, which accounted for chitosan deacetylation, were detected. Furthermore, crosslinking reactions occurred, as revealed by gel fraction characterization. Variations in the mechanical and surface properties were characterized by AFM, and the reduction in macroscopic properties was correlated with the structural changes observed at the molecular scale by a multiscale approach.

Automated summary

Chitosan films were subjected to accelerated artificial weathering in the presence of oxygen, resulting in changes in chemical structure, formation of gluconolactone derivatives, detection of low molecular weight photoproducts, occurrence of crosslinking reactions, and variations in mechanical and surface properties. These changes were observed and correlated at molecular scale, showing a reduction in macroscopic properties.