Handbook of Size Exclusion Chromatography and Related ...

the normal CMC (about 0.002g/mL), and charging the PVP,turning it into a
polyelectrolytewhoseA2increasesaslinearchargedensityincreases,leadingtothe
decrease in scattered intensity,according to Eq. (3). Similarly,the charging of the
PVP leads to an electrostatically based expansion of the polymer coil, increasing
thehydrodynamic volume(and henceviscosity). The inset to Fig.13a shows how
the scattering intensity increases for fixed concentration PVP saturated by SDS (1%
SDS) as [NaCl] increases. The increase in the scattered intensity is due to the ionic
shielding between the charged PVP chains, leading to a decrease in A2. The
viscosity (not shown) likewise decreases as [NaCl] increases. In the absence of
SDS, the scattering and viscosity behavior of PVP are independent of [NaCl].
Figure 13b shows the complex way scattering intensity varies as the
concentration of PVP saturated with a fixed concentration of SDS increases.
The maxima reached are due to the effect of A3, which can be computed from the
value of cp at which the maximum occurs at q ¼ 0, cp,max,q¼0, according to
1
A3 ¼
3Mwc2 p,max,q¼0
(24)
Figure 14 The value of the association constant r (mass of SDS bound per mass of PVP)
vs. [NaCl], at saturating levels of SDS. Also shown is A2 which decreases strongly with
[NaCl] due to ionic shielding. (From Ref. 70.)
© 2004 by Marcel Dekker, Inc.