Effect of counterions on complex coacervation

In a recent paper, we developed a thermodynamic theory on the complex coacervation in the absence of low molecular ions, under the assumption that the coacervation is a condensation phenomenon of aggregates of polyanion and polycation in the aqueous solution, by obtaining the interaction potential U_S between these aggregates on the basis of Flory's method. In this paper, we have extended the theory to a more complicated phenomenon of the counterion-containing solutions. This treatment has led the interaction potential having an additional contribution to U_S resulting from an entropy increase by the counterion distribution. The phase diagram between solution (sol) and separated phase has been obtained as a function of the difference of charges between polyanion and polycation. It has been found that the presence of counterions sensitively suppresses the coacervation.