SOLUTION PROPERTIES OF CHITOSANS - CONFORMATION AND CHAIN STIFFNESS OF CHITOSANS WITH DIFFERENT DEGREES OF N-ACETYLATION

Chitosans with degrees of N-acetylation, F(A), ranging from 0 to 0.6 were randomly degraded to different molecular weights and characterized by measuring intrinsic viscosities and osmotic pressure. In order to determine the stiffness parameter, B and the Mark-Houwink-Kuhn-Sakurada (MHKS) equations at different ionic strengths, intrinsic viscosities were measured at various ionic strengths. The Kuhn lengths at theta-conditions, A(mtheta), were estimated from an interpolation utilizing the obtained stiffness parameters and a published relation between B and A(mtheta) for different polyelectrolytes. These values were then used to compute the characteristic ratios, C(infinity), which are defined at theta-conditions. From the Flory-Fox viscosity relationship and a theory of Bloomfield and Zimm, the radii of gyration, R(G), and also the Kuhn lengths at different ionic strengths, A(mI). were calculated. In order to investigate the influence of the N-acetyl groups in contrast to the polyelectrolyte effect of the NH3+- group on the overall conformation, the intrinsic viscosity data were extrapolated to infinite ionic strength, and the resulting MHKS equations, the R(Ginfinity) and the A(minfinity) were estimated.