Charge-stabilized suspensions of spherically shaped particles show a variety of interesting properties. As a consequence, there has been considerable interest in the investigation of the microstructure and the dynamic properties of well characterized model systems, such as polystyrene spheres dispersed in water and charged silica spheres dispersed in an organic solvent. Among various experimental techniques, static and dynamic light scattering have been the major tools for the characterization of colloidal suspensions. Whereas there is an essentially quantitative understanding of monodisperse suspensions, only very recently good progress was achieved, both theoretically and experimentally, in understanding certain properties of colloidal mixtures and intrinsically polydisperse one-component suspensions. Colloidal mixtures show additional phenomena, e.g., a variety of microstructures and phase behaviour, tracer-diffusion and interdiffusion, which do not exist in monodisperse systems. This article offers a survey on our current knowledge of the dynamics and statics of charge-stabilized suspensions in the fluid phase, with emphasis on the authors own work. It further contains a summary of basic concepts, and of analytical and numerical methods, which are relevant for the theoretical description of charge-stabilized suspensions. Special effort is made to point out the salient differences between colloidal mixtures and monodisperse suspensions. The calculated or computer-simulated quantities characterizing the suspensions are compared, whenever available, with the results of light scattering experiments. The article is divided into two major parts. The first part (chapters 2 and 3) is concerned with static properties. It includes a discussion of the origin of the repulsive and attractive forces between charged colloidal particles, the concepts of the effective charge and global correlation functions, the influence of the finite size of the counterions on the microstructure of concentrated ionic micellar solutions, and the extension of the rescaled mean spherical approximation to colloidal mixtures. The central issue of the first part is, however, the theoretical modeling of intrinsic polydispersity, and the calculation of static structure factors and radial distribution functions by various integral equation methods. The relative accuracy of these methods is assessed from the comparisons with computer simulations and light scattering results. The main body of this article is contained in the second part (chapter 4), which is concerned with the dynamics of charge-stabilized suspensions. A thorough discussion of the various levels of description of the suspension dynamics is given in terms of the time scales characterizing various relaxation processes associated with the colloidal particles and the molecules of the host fluid. The description of the dynamics of the colloidal particles, based on the generalized Smoluchowski equation, is justified for the time interval accessible in dynamic light scattering experiments. A summary of general properties of the generalized Smoluchowski equation is provided, and various ordering relations for diffusion coefficients are presented. The combined influence of the electrostatic and solvent mediated hydrodynamic interactions on the short-time dynamics of monodisperse and polydisperse charge-stabilized suspensions is investigated in great detail. It is shown that the effect of hydrodynamic interaction is strongly enhanced by the presence of long-ranged electrostatic repulsion, and its influence is more pronounced for collective diffusion than for short-time self-diffusion. The additional influence of polydispersity is found to be quite significant. Finally, a thorough study of tracer-diffusion in charge-stabilized suspensions is presented. Mean square displacements and long-time tracer-diffusion coefficients are calculated with two alternative approximations, i.e., a mode-coupling scheme and a single relaxation time ansatz. The range of validity of these approximations is assessed by numerous comparisons with Brownian dynamics simulation results, and with large-wavenumber dynamic light scattering and forced-Rayleigh data. It is observed that tracer-diffusion is quite sensitive to the amount of intrinsic polydispersity.
