Preparation, water solubility and rheological property of the N-alkylated mono or disaccharide chitosan derivatives

N-alkylation of chitosan was performed in a mixture of methanol and 1% acetic acid containing different amounts of mono-saccharides or disaccharides including glucose, galactose, glucosamine, fructose, lactose, maltose and cellobiose. All the N-alkylated chitosan derivatives with monosaccharides were insoluble in aqueous solution (pH 7), while N-alkylated chitosan derivatives with disaccharides were easily soluble in distilled water, and the N-alkylated chitosan derivatives with lactose were soluble only at high pH. The degree of substitution (DS) of the N-alkylated chitosan derivatives increased with increasing disaccharides levels and with increasing reaction time. The reduced viscosity of the N-alkylated chitosan derivatives with disaccharides decreased with increasing DS. Apparent viscosity and pseudoplasticity of the N-alkylated disaccharide containing derivative solutions generally decreased with increasing DS. Although apparent viscosities of N-alkylated chitosan derivatives with low DS decreased with increase in pH or ionic strength, changes in high DS N-alkylated chitosan derivatives with pH values or ionic strength were not marked. (C) 2002 Elsevier Science Ltd. All rights reserved.