Determination of colloidal interaction potentials from small angle scattering data

The scattering curves of monodisperse, globular particles measured by small angle scattering are products of a form factor and of a structure factor. The form factor contains the information on particle shape and size and can often be measured for dilute samples. The structure factor contains the contributions due to particle interactions. It should be approximated by a structure factor model based on the Percus-Yevik, hypernetted chain, or soft mean spherical approximation closure relations. Combining these relations with a flexible model for the interaction potential, it is possible to determine the interaction potential from the scattering data. Scattering curves of charged spherical colloids and of spheres interacting by depletion forces are therefore simulated and evaluated, resulting in potentials that are close to the ones used for the simulation. The applicability of the approach is finally tested on a 5% solution of lysozyme at pH 4.5, which gave an interaction potential that agreed well with the one expected for such a sample.