Rheological properties of microcrystalline chitosan gels

The procedure of thermocatalic processing of chitosan developed allows one to decrease its degree of polymerization to the so-called leveling-off degree and, after the precipitation from a solution and washing, to obtain hydrogels of microcrystalline chitosan (MCC.) The flow curves of the MCC gels showed that a spatial structure was formed in the gels even at low their concentrations. The measurements of vicoelastic properties of the dispersions verified the existence of such a structure. It is shown that, at MCC concentrations above 3%, a transition from the isotropic phase to a liquid-crystalline one occurs. For comparison, the flow properties of chitosan solutions in acetic acid were studied too. The measurements showed that, at the solution concentrations considered, they did not exhibit liquid-crystalline rheological properties.