Charged colloids and proteins: Structure, diffusion and rheology

This thesis comprises a theoretical description of the microstructure, diffusion and rheological properties of dispersions of charged Brownian particles. We have developed, and thoroughly tested, various analytical theoretical methods to calculate static and dynamic properties, and have applied them to various experimental systems. The common features of these analytic methods are their high levels of accuracy, versatility, and numeric efficiency. We have calculated a large variety of equilibrium and short-time dynamic properties and also some long-time properties, including static structure factors, translational collective and self-diffusion coefficients, hydrodynamic functions, and static and high-frequency shear viscosities. Suspensions of synthetic silica spheres, moderately aspheric bovine serum albumin proteins, and thin gibbsite platelets have been examined in collaboration with experimental groups in Jülich, Tübingen, Utrecht (Netherlands) and Košice (Slovakia). (Dynamic) Light- and X-ray scattering data, and shear viscosities for these systems have been calculated for concentrations up to the liquid-solid or liquid-liquid crystal phase transition point, allowing for a detailed characterization of the suspended particles. In comprehensive parameter studies, we have validated our analytic methods of calculating equilibrium pair-correlations and (short-time) dynamics against numerous computer simulation results. The computer simulations were conducted by Prof. Banchio (Uni. Córdoba, Argentina), in the course of an extended collaboration. A model of monodisperse, charged Brownian spheres, suspended in a structureless fluid, and interacting via a screened Coulomb potential, serves as the basis of our analytic schemes. The salt content of the suspension affects the range of electrostatic repulsion, which can cause pronounced pair correlations in low-salinity systems at very low colloid concentrations. An important advancement of this thesis is the development of a new analytic integral equation scheme, named Modified Penetrating Background corrected Rescaled Mean Spherical Approximation, which allows for fast and accurate calculation of static pair correlations. The pair correlation functions computed by this method serve as input for various analytic methods of calculating diffusion properties, and static and high-frequency shear viscosities of chargestabilized suspensions. A severe complication in computing dynamic properties arises from the necessary inclusion of long-ranged, non-pairwise additive hydrodynamic interactions. To this end, we provide [...