Solution properties of chitosans: conformation and chain stiffness of chitosans with different degrees of N-acetylation

Chitosans with degrees of N-acetylation, FA, 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 θ-conditions, Amθ, were estimated from an interpolation utilizing the obtained stiffness parameters and a published relation between B and Amθ for different polyelectrolytes. These values were then used to compute the characteristic ratios, C∞, which are defined at θ-conditions. From the Flory-Fox viscosity relationship and a theory of Bloomfield and Zimm, the radii of gyration, RG, and also the Kuhn lengths at different ionic strengths, AmI, 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 RG∞, and the Am∞ were estimated.