Donnan equilibria of simple electrolytes in polyelectrolyte solutions. Part 2.—Extension to polycations and the effect of charge densities

Abstract

Salt exclusion parameters Γ[=(m^′_s–m_s)/m_e, where m_e denotes the polyelectrolyte concentration, m_s and m^′_s represent the salt concentrations of the solutions with and without polyelectrolyte] of polyelectrolyte–simple salt solutions have been determined for poly(2-methacryloxyethyltrimethylammonium) chloride (PMETAC), polyallylamine hydrochloride (PAAm), partially neutralized polyacrylate (PA) and sodium polystyrenesulfonate (NaPSS). For PA, Γ was examined at differing polyelectrolyte charge densities. An empirical equation with a single parameter k, Γ=k/[1 +(1 +kx)^1/2], where x=m_e/m_s, described the results to a good approximation. An empirical but unique relation was obtained between the k values and the osmotic coefficient in salt-free polyelectrolyte solutions, ϕ_p, irrespective of the polymers and salts, when the present results were supplemented with previous data.