2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) was prepared by the reaction of chitosan with 2,3-epoxypropyltrimethyl ammonium chloride. The effect of pH in reaction mixture on yield and solubility of the products was investigated, and reaction mechanism was discussed. HPLC was used to characterize the change of molecular weight. The results showed that the yield of water soluble HACC was higher at pH 6. 0 than at pH 4. 0, 7. 0 and 9.0, respectively. And the molecul...