Synthesis of Soluble Carboxymethyl Chitosan from Low Molecular Weight of Chitosan

Abstract

Carboxymethyl chitosan was obtained under heterogeneous conditions as a product of the reaction of chitosan and monochloroacetic acid in the presence of sodium hydroxide. In the previous experiment, showed that the solubility of carboxymethyl chitosan increased with the decreased of molecular weight of chitosan. However, the  solubility of carboxymethyl chitosan in water and acid solvent  were still necessary to be maximized.  In this experiment aims to determine the effect of condition process such as NaOH concentration, mass ratio chitosan to monochloroacetic acid, and time eterification towards degree of substitution (DS) and the solubility of carboxymethyl chitosan. Some variables that were used to synthesize carboxymethyl chitosan were concentrations of sodium hydroxide (20-50 %w/v), etherification times (1-4 hr), and mass ratio chitosan to monochloro acetic (1:1, 2:1 and 1:2 (v/v). Characterization performed on the synthesized carboxymethyl chitosan including FTIR, degree of substitution (DS), and solubility properties. The solubility of carboxymethyl chitosan increased almost linearly with increasing concentration and etherification times. The maximum DS value being obtained for carboxymethyl chitosan sample synthesized in 50% (w/v) sodium hydroxide with 4-hour reaction and temperature at 60^oC, that is 1.79 and solubility of carboxymethyl chitosan were 86.3%; 95.2%; 92.3% in water, 1% of HCl and 1% of CH_COOH respectively.