Thermodynamic properties and phase equilibria of charged hard sphere chainmodel for polyelectrolyte solutions

A recent thermodynamic perturbation theory for flexible polyelectrolyte sol utions is extended to study thermodynamic properties and phase equilibria f or polyelectrolyte solutions with different polyion chain lengths. Osmotic pressure, activity coefficient of an individual ion (polyion or counterion) and average activity coefficient are calculated. Except for the activity c oefficient of the polyion, the chain length dependence of the properties is small. Also presented are vapour-liquid equilibrium coexisting curves, vap our pressures and critical points. As the polyion chain length approaches i nfinity the critical properties (temperature, pressure and density) become constants.