Colloidal Systems with Attractive Interactions: Evaluation of Scattering Data Using the Generalized Indirect Fourier Transformation Method

Abstract

Different attractive interacting colloidal systems are characterized by means of static light scattering. As most of these samples are rather concentrated, multiple scattering is suppressed by partial contrast match and the use of very a thin sample cell (13 μm). This is possible with the laboratory built flat cell light scattering instrument, which is also capable of time-resolved measurements. The systems under investigation are oil-in-water emulsions with added polymer micelles or latex spheres, which give rise to depletion interaction. A second set of samples consists of electrostatically stabilized dense silica suspensions, which are destabilized by ionic strength or pH shift initiated by an in-situ reaction. The potential change from repulsive to attractive is measured time-resolved in real time. These suspensions are model systems for the so-called direct coagulation casting (DCC) method. Scattering data are evaluated using the generalized indirect Fourier transformation (GIFT) method. We added some new routines for calculating structure factors for attractively interacting systems to the already existing software package. We now can choose between a depletion interaction and an attractive square well potential, which was used for the DCC samples. The obtained results are in good agreement with the values known from preparation for the depletion samples and those predicted from DLVO calculations for the DCC series, respectively.