Modeling colloidal interactions using structural data: Insights from coated silica dispersions

Some questions raised by the modeling of the interactions between colloids using scattering data are examined. After a brief overview of the predictions and limitations of the basic potentials with short-range attraction, we first analyze recent data on coated silica dispersions, using a model with short-ranged repulsion and an improved treatment of the short-ranged attraction. We discuss in particular the unicity of the potential extracted from the structural data, the state dependence of the fitting parameters and their link with the characteristics of the particles, the effect of the particle size, and the density and temperature in pure components and in mixtures. The analysis of the data in the silica dispersions is next confronted with charged colloids and star polymers. Based on the prediction for the position of the main peak of the scattering intensity in six dispersions at different state points, the possible role of many-body effects in the scattering intensity is confirmed. Finally, the use of gelation data for refining the potential extraction is discussed.