Abstract: N,N,N-trimethyl chitosan methylsulfate (TMCMS) was prepared by a two-step reaction. First, N,N-dimethyl chitosan (DMC) was synthesized by reaction of chitosan with formic acid and formaldehyde. Then, DMC reacted with dimethyl sulfate to yield TMCMS. It was characterized by FT-IR, 1H NMR and elemental analysis. Its average quaternization degree was 74.6% calculated according to elemental analysis results. Differential scanning calorimetry and thermogravimetry results demonstrated its thermal stability was lower than chitosan. However, its water-solubility was obviously better than chitosan, its solubility in water reached 20 mg/mL at 25 ℃, and its 2 mg/mL solution was stable in a wider pH range (3-12).

Key words: chitosan, dimethyl sulfate, N,N,N-trimethyl chitosan methylsulfate, quaternary ammonium salt, synthesis