An in-situ reactor was elaborately designed for O-alkylation of chitosan in an ionic liquid ([BMIM]Cl) solvent, using N, N'-carbonyldiimidazole as bonding agent. The original chitosan and the modified chitosan were characterized by FT-IR and XRD analysis. FT-IR spectra revealed that the alkylation of chitosan selectively occurred at hydroxyl groups, with unprotected amino groups untouched. It was proposed that the particular properties of the ionic liquid solvent should be responsible for the selectively alkylation. The result from X-ray diffraction showed that the crystallinity of O-alkylation of chitosan decreases, most likely due to the decomposition of CS in the ionic liquid. The solubility test of O-alkylated chitosan in aqueous HAc solution (w/w: 0.1%) confirmed that the product could be easily dissolved in aqueous HAc solution because of its abundant free amino groups. It was suggested that the O-alkylated chitosan was suitable for the coming cell transfection test in vitro.
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