Multi-crosslinked network chitosan films containing caffeic acid and Fe3+ with high anti-oxidation and anti-UV abilities

In this study, caffeic acid (CA) and Fe3+ were added to chitosan solution to prepare chitosan/caffeic acid/Fe3+ (CCAF) composite films. CA was used to introduce covalent bonds and hydrogen bonds. Fe3+ was used to introduce metal coordination bonds which combined with hydrogen bond and covalent bonds to form a multi-crosslinked system to enhance the tensile strength (TS), improve the antioxidant properties and UV resistance performance. The results showed that the TS of chitosan/caffeic acid (CCA) film with the addition of 0.3 mmol CA was increased by 36.6 % compared with pure chitosan film. The TS of the CCAF film increased from 42.6 MPa to 73.9 MPa with an increase of 73.5 %. The free radical scavenging rate of CCA film and CCAF film, in comparison to pure chitosan film, were improved by 155.7 % and 148.24 %, respectively. The UV resistance property of the CCAF solution was tested at 365 nm and the results showed that the UV barrier rate reached 99.99 %. The water vapor transmission (WVT) and water vapor permeability (WVP) of CCAF film both showed a 25.71 % reduction compared to that of the chitosan film. Besides, the composite film also showed excellent antibacterial properties, which provided the possibility for more applications.