Synthesis, characterization and slow release properties of O-naphthylacetyl chitosan

O-naphthylacetyl chitosan (NA-chitosan) was first prepared via protecting the amino groups with phthalic anhydride, followed by reaction with 1-naphthylacetyl chloride. The intermediates were hydrolyzed with anhydrous hydrazine to obtain final product. The derivatives of each step were characterized with Fourier transform infrared spectroscopy (FT-IR) and 13C solid state nuclear magnetic resonance (NMR). Results showed NA-chitosan had both naphthylacetyl and amino groups in the main chain of the polysaccharide. Elemental analysis showed that the substitution degree of hydroxyl was 0.4. Thermogravimetric analysis (TGA, DTG) of NA-chitosan was observed with much lower decomposition peak at 283 °C than that of chitosan at 300 °C. The release of 1-naphthylacetic acid was dependent on both pH values and the medium temperature, and at pH 12.0, 60 °C the release period could last for 55 days.