Abstract
Marco Heinen: „Analytic theory of charged colloids and proteins”
IFF Jülich
Systems of charged colloids and globular proteins are studied within the model of Brownian spheres interacting directly by a Yukawa-like pair-potential and indirectly by solvent-mediated hydrodynamic forces. The solvent is described as a structureless overdamped fluid, coupled to the particles by hydrodynamic boundary conditions. A novel analytic integral equation scheme for the equlibrium pair-structure in the colloidal fluid phase is presented. This so-called MPBRMSA method allows for a fast computation of the static structure factor with excellent accuracy. Thereby, convenient real-time fitting of experimental data becomes possible, as well as a fast delivery of microstructural input to dynamics theories. A hybrid scheme of short-time dynamics is constructed, which includes non pairwise-additive hydrodynamic interactions in an approximate way. Diffusion properties and the suspension viscosity are calculated with good accuracy in the full liquid regime, as demonstated by comparisons with computer simulations. Static (long-time) shear viscosities of dispersions with moderate structural ordering are calculated in a simplified mode-coupling scheme. The set of static and dynamic theories is used to investigate suspensions of silica and PMMA spheres, PNIPAM microgels, and BSA proteins.