STATIC STRUCTURE FACTORS OF BINARY SUSPENSIONS OF CHARGED POLYSTYRENE SPHERES - EXPERIMENT AGAINST THEORY AND COMPUTER-SIMULATION

The microscopic static structure of dilute binary colloidal suspensions, for compositions covering the full molar fraction range, are investigated using static light scattering experiments. The mixtures of liquid-like ordered suspensions are made from charged polystyrene particles having averaged radii of 42 nm and 65 nm. The data are compared with the results of integral equation theories using the extended re-scaled mean spherical approximation and the hypernetted chain approximation and Rogers-Young closure schemes, and to Monte Carlo computer simulations. The values of charges needed in the Yukawa-type pair potentials arc determined from fits to the scattering data of the pure components, and they are kept constant for the mixtures. Of the various theoretical schemes used, the Rogers-Young method is found to be the most satisfactory. In order to fully describe the experimental data, it is necessary to take the intrinsic polydispersity of the two pure components into account.