Macroions in Solution

Abstract

In this chapter we review models and theories suitable for studying polyelectrolytes in solution. The theories were applied to various problems: a) the first is the catalytic effect on the reaction between small ions of the same charge sign, caused by addition of a polyelectrolyte to an electrolyte solution. In the next example b) we studied the stability of polyelectrolyte solutions. For highly charged systems, and/or in presence of multivalent counterions, computer simulations and recent experimental data predict clustering of macroions. The new computer simulation data support the assumption that a partial neutralization of macroions is the first step in the process of macroion clustering. In the third example c) we considered low-charge polyelectrolytes where the effects of solvent seemed to be important. We present results for a new model of a polyelectrolyte solution with the chain-like polyions where the solvent molecules, approximated as two fused charged hard spheres, are explicitly included in the calculation. This model yields osmotic pressure results in good qualitative agreement with experiment. In the last example d) we consider the Donnan membrane equilibrium in protein solutions. The theory is used to analyze experimental data for the Donnan pressure in solutions of various proteins.