CHITOSAN BEHAVIORS IN A DISPERSION OF UNDECYLENIC ACID - STRUCTURAL PARAMETERS

As a complement to a first paper (Demarger-Andre and Domard, 1993), th e influence of Structural parameters (degree of acetylation, DA and mo lecular mass, (M) over bar(v)) of chitosan was investigated in the stu dy of flocculation and redispersion of undecylenic acid dispersions. T hese phenomena were studied by UV spectroscopy, QELS and SEC. The floc culation/redispersion process does not seem to depend upon the DA, as long as the concentration of glucosamine residues is constant in the c hitosan solutions used. This suggests a mechanism of electrostatic int eractions. When (M) over bar(v) increases, less chitosan is necessary to flocculate and redisperse the system. and the size of the redispers ed particles increases. Adsorption studies based on Langmuir's model s how that within a wide range of (M) over bar(v), one major mechanism o f adsorption is involved in the redispersion process, namely electrost atic interactions of the mosaic type. Above a critical mass another me chanism of interaction occurs, which should be polymer bridging betwee n various particles.