Synthesis, characterization, and application of films made from highly substituted N-perfluoroacylated chitosan

Highly substituted perfluoroacylated chitosan can alter the physicochemical properties of chitosan; however, the currently synthesized perfluoroacylated chitosan has a low degree of substitution. In this study, we present a simple method for the homogeneous preparation of highly substituted N-perfluoroacylated chitosan, conducted at room temperature without requiring strict anhydrous or oxygen-free conditions. Various perfluorocarbon chains were successfully attached to chitosan through a reaction between perfluorinated acid esters and amines, catalyzed by DBU. The synthesized N-perfluoroacylated chitosan, with high degree of substitution, demonstrated excellent solubility in common organic solvents. Comprehensive characterization was performed using elemental analysis, nuclear magnetic resonance (including two-dimensional NMR), gel permeation chromatography, infrared spectroscopy, X-ray diffraction, and thermal analysis. The resulting films exhibited high water contact angles. Notably, as the fluorocarbon chain length increased, tensile strength gradually decreased, while elongation at break improved. Additionally, water uptake, water vapor transmission rate, and oxygen transmission rate all exhibited a declining trend. The films exhibited good biocompatibility, and in the grape preservation experiment, HFBC treatment effectively delayed grape aging and deterioration while enhancing quality preservation. These results suggest that HFBC film holds promising potential for food packaging applications.