PREPARATION AND NMR CHARACTERIZATION OF HIGHLY SUBSTITUTED N-TRIMETHYL CHITOSAN CHLORIDE

N,N,N-Trimethyl chitosan chloride (TMC) is a chemically modified chito san with improved aqueous solubility, compared with the native chitosa n. It is essential to follow a synthesis procedure in which the degree of substitution of the final product can be controlled by means of th e number of reaction steps, the duration of each reaction step and the amount of methyl iodide as reagent. A two-step reaction yields produc ts with high degrees of substitution (40-80%). Comparison of the NMR s pectra of the product TMC, after a two-step reaction, indicates that t here is a peak assigned to the substituted amino group that shifts fro m 2.5 to 3.1 ppm upon acidification. This peak must be assigned to N(C H3)(2) and not to N(CH3)(3)(+). A three-step reaction procedure yields products with a degree of substitution > 80%, but with substantially decreased water-solubility. (C) 1998 Elsevier Science Ltd. All rights reserved.