CHITOSAN BEHAVIORS IN A DISPERSION OF UNDECYLENIC ACID - STRUCTURAL PARAMETERS

As a complement to a first paper (Demarger-Andre and Domard, 1993), the influence of Structural parameters (degree of acetylation, DA and molecular mass, (M) over bar(v)) of chitosan was investigated in the study of flocculation and redispersion of undecylenic acid dispersions. These phenomena were studied by UV spectroscopy, QELS and SEC. The flocculation/redispersion process does not seem to depend upon the DA, as long as the concentration of glucosamine residues is constant in the chitosan solutions used. This suggests a mechanism of electrostatic interactions. When (M) over bar(v) increases, less chitosan is necessary to flocculate and redisperse the system. and the size of the redispersed particles increases. Adsorption studies based on Langmuir's model show that within a wide range of (M) over bar(v), one major mechanism of adsorption is involved in the redispersion process, namely electrostatic interactions of the mosaic type. Above a critical mass another mechanism of interaction occurs, which should be polymer bridging between various particles.