Av. Dobrynin et M. Rubinstein, Counterion condensation and phase separation in solutions of hydrophobic polyelectrolytes, MACROMOLEC, 34(6), 2001, pp. 1964-1972
We have developed a theory of counterion condensation in solutions of hydro
phobic polyelectrolytes. In the framework of Oosawa's two-zone model we dem
onstrate that solutions of necklaces can be unstable with respect to phase
separation. This phase separation is triggered by the concentration-induced
counterion condensation. For the range of parameters at which the polyelec
trolyte solution is stable, we predict nonmonotonic dependence of the chain
size on polymer concentration. This nonmonotonicity in the chain size mani
fests itself in the dramatic increase in solution viscosity at the crossove
r to concentrated polyelectrolyte solution. There is also a possibility of
two peaks in the scattering function of qualitatively different physical na
ture observed in different concentration regimes. The scattering intensity
at the peak position increases with polymer concentration in low concentrat
ion (necklace) regime and decreases with concentration in concentrated poly
electrolyte solutions.