Abstract
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.
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