THE TIME-DEPENDENCE OF CHITOSAN NONIONIC SURFACTANT SOLUTION VISCOSITY

The measurement of the viscosity of semiconcentrated chitosan (0.08-0. 14%) solutions in the system with octaethyleneglycol mono n-dodecyleth er (C(12)E(8)) was carried out using Cannon-Fenske capillary viscomete r. The interaction was - as expected - very weak, but when the time de pendent hydrodynamic behaviour of the system was considered, the inter action has been established at particular surfactant concentrations. T he most significant time dependence is shown in a form of sudden visco sity drop in a region close to and above CMC value of the surfactant, which implied existence of the interaction between chitosan and surfac tant. At low surfactant concentrations viscosity values vere constant with increasing surfactant concentration, but solution also showed tim e dependent decrease in the viscosity which has been connected with we ll known time dependent viscosity of pure chitosan solution. The visco metry enabled monitoring of the extent of chitosan/surfactant associat ion by establishing the viscosity decrease rate constant. The rate con stant was derived from the first order constant of the quadratic polyn omial curves used for the approximation of experimental values when th ese are presented in the form of viscosity-time profiles. This method showed the existence of critical surfactant concentration values (C-1, C-2, and C-3) These values are closely connected with the proposed in teraction model which is based on the assumption that spherical surfac tant micelles are bound by chitosan molecule.