Frozen-in Intensity Fluctuations of Light Scattered by Partially Ionized Gels

We report results of static light scattering for partially ionized gels at different cross-link densities and different swelling degrees and for the corresponding semi-dilute solutions. The r.m.s. fluctuations of the scattered intensity obtained when scanning through various positions in the gels is proportional to the excess of scattering of the gel with respect to the semi-dilute solution, whatever the method used to vary the ratio of the actual swelling degree to its equilibrium value, i.e. varying the cross-link density or the swelling extent. The excess of scattering is attributed to a frozen-in component associated with scattering domains with a spatial extent less than ∼ 300 Å.