CHARACTERIZATION OF CHITOSAN - INFLUENCE OF IONIC-STRENGTH AND DEGREE OF ACETYLATION ON CHAIN EXPANSION

This paper concerns a new method of characterizing chitosans with different degrees of acetylation (DA = 2, 11.5 and 21%); it consists of steric exclusion chromatography using a multidetection instrument allowing determination of M, [eta] and R(G) for each point of the chromatograms. From these data, the Mark-Houwink parameters for intrinsic viscosity and the exponent relating R(G) and M are determined In the same way, the role of the solvent is discussed and the solvent AcOH 0.3 M/AcONa 0.2 M is proposed to reduce the presence of aggregates which perturbs static molecular weight determination by light scattering. The role of the ionic concentration and of the degree of acetylation on the stiffness of chitosan is then discussed and a theoretical treatment is proposed allowing the determination of.the intrinsic persistence length (L(p) = 50 angstrom) and the prediction of the dimensions in solution (R(G) and [eta]). L(p) is found to be independent of DA in the range tested.