Effect of N-acylation on structure and properties of chitosan fibers

This article described the physico-chemical transition of the chitosan fibers by N-acylation. N-Acyl chitosan fibers were prepared by a post-treatment of chitosan fibers with carboxylic anhydrides (e. q., acetic, propionic, butyric, hexanoic anhydride) in methanol at room temperature. N-Acyl chitosan fibers were analyzed by FT-IR, TGA, DSC, XRD and SEM. N-Acylation with longer hydrocarbon side chain resulted in a higher spatial organization of the chain to the long axis and showed lower moisture retention. The N-acyl chitosan fibers with short acyl chain exhibited gradually lower tensile strength. N-Hexanoyl chitosan fibers showed higher tensile strength than N-acetylated ones. The chemical structure of chitosan fibers was gradually altered from hydrated form (anti-parallel structure) to dehydrated form (parallel structure) with a treatment of carboxylic anhydrides.