Objective Cellulose-based films have demonstrated significant potential as substitutes for traditional plastics. However, cellulose films are typically characterized by limited functionality. Janus films possess unique asymmetric interfacial wettability, enabling them to overcome the limitations of traditional films. However, the current single-sided chemical modification method and in-situ fixation method still have obvious drawbacks. In view of this, we took advantage of the fact that cellulose and chitosan have different solubilities in solvents to prepare Janus film by a one-step molding method, achieving the functionalization of cellulose-based films.

Method Aldehyde-functionalized cellulose was synthesized via the selective oxidation of cellulose in the presence of sodium periodate. Based on different solubility of cellulose and chitosan in the N,N-dimethylacetamide/lithium chloride solvent systems, Janus oxidized cellulose/chitosan films with an asymmetric structure were fabricated through the Schiff base reaction. The as-prepared films were comprehensively characterized and evaluated for their performance using infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis, etc. Also, the water-holding capacity, swelling ratio, contact angle, and antibacterial activity were determined.

Result The Janus films featured a dual-sided heterogeneous structure, where the chitosan side exhibited significantly higher roughness compared with the oxidized cellulose side. The contact angle of oxidized cellulose side was below 75°, whereas that of the chitosan side exceeded 99°. This film demonstrated remarkable antioxidant properties with a maximum DPPH radical scavenging rate of 83.28%. Its elongation at break can reach up to 113.90%, and a film (5 cm × 1 cm) can support 0.5 kg. Furthermore, the Janus film displayed excellent thermal stability, anti-swelling characteristics, antibacterial activity against Escherichia coli and Staphylococcus aureus, as well as effective UV-blocking performance.

Conclusion Based on the complementary functionalities of cellulose and chitosan, multifunctional Janus oxidized cellulose-chitosan films are successfully fabricated via the Schiff base reaction. These films exhibit pronounced disparities in hydrophilicity/hydrophobicity and surface microstructure, and demonstrate excellent performance in terms of antioxidant capacity, mechanical performance, anti-swelling behavior, and thermal stability, rendering it highly promising for applications in packaging and biomedicine.