6533b7d1fe1ef96bd125d500

RESEARCH PRODUCT

Static and dynamic light scattering by aqueous polyelectrolyte solutions: effect of molecular weight, charge density and added salt

subject

description

Abstract Aqueous solutions of quaternized poly(2-vinylpyridine) were investigated by static (SLS) and dynamic (DLS) light scattering over a wide range of polyelectrolyte, c pe , and salt concentrations, c s (10 −3 ≤ c pe ≤ 10 2 gl −1 , 10 −5.5 ≤ c s ≤ 10 −1 moll −1 ). Using DLS the cooperative diffusion coefficient D was measured as a function of c pe and c s . D exhibits a characteristic behaviour in each of three different concentration regimes. In the ‘dilute lattice’ regime, where λ = c pe c s ⪡ 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.