Effect of hydroxyethylation on structure and properties of chitosan fibers

Chitosan fibers were modified with epoxyethane in the presence of sodium hydroxide to enhance the capability of water absorbency. This property offers potential application as wound dressings with enhanced capability to absorb wound exudates. Four fiber samples with different degree of substitution (DS) were prepared by changing the mole ratio of epoxyethane to glucosamine repeat units (GIcN). The resultant fibers were characterized by FTIR, C-13 solid-state NMR, TGA, XRD, and SEM. The FTIR and C-13 NMR spectra indicated that hydroxyethyl groups were mainly attached to C-6 positions. The inter- and intra-hydrogen bonding were broken while the crystallinity remained unchanged, indicated by FTIR and XRD results. TGA analysis showed that thermal stability decreased as DS increased. The modified chitosan fibers with increased hydrophilic hydroxyethyl groups exhibited lower tensile strength and elongation than initial chitosan fibers. Hydroxyethylation with lower DS enhanced the water absorbency of chitosan fibers while maintaining their fibrous structures.