STATIC AND DYNAMIC LIGHT-SCATTERING BY AQUEOUS POLYELECTROLYTE SOLUTIONS - EFFECT OF MOLECULAR-WEIGHT, CHARGE-DENSITY AND ADDED SALT

Aqueous solutions of quaternized poly(2-vinylpyridine) were investigated by static (SLS) and dynamic (DLS) light scattering over a wide range of polyelectrolyte, cpe, and salt concentrations, cs (10-3 ≤ cpe ≤ 102 gl-1, 10-5.5 ≤ cs ≤ 10-1moll-1). Using DLS the cooperative diffusion coefficient D was measured as a function of cpe and cs. D exhibits a characteristic behaviour in each of three different concentration regimes. In the 'dilute lattice' regime, where λ = cpe cs ≪ 1, one diffusion coefficient is observed. In the transition regime, where λ ≈ 1, D increases with increasing polyelectrolyte concentration and a slow diffusive mode gradually appears. For λ ≫ 1 ('semidilute lattice regime') a fast diffusive process, which is interpreted as the gel mode of a transient network, and a slow diffusive process, which is associated with long-range concentration fluctuations, are observed. For the dynamic behaviour, the absolute ionic strength of the solution is only of minor importance. © 1990.