Rigorous calculations of linearized Poisson-Boltzmann interaction between dissimilar spherical colloids and osmotic pressure in concentrated dispersions

Abstract

We present computational results on the static properties of concentrated dispersions of bidisperse colloids. The long-range electrostatic interactions between dissimilar spherical colloids are determined using the singularity method, which provides rigorous solutions to the linearized electrostatic field. The NVT Monte Carlo simulation is applied to the bulk suspension to obtain the radial distribution function for the concentrated system. The increasing trend of osmotic pressure with increasing total particle concentration is reduced as the concentration ratio between large and small particles is increased. The increase of electrostatic interaction between similarly charged particles caused by the Debye screening effect provides an increase in the osmotic pressure. From the estimation of total structure factor, we observe the strong correlations developed between dissimilar spheres, and the small spheres are expected to tend to fit into the spaces between the larger ones. As the particle concentration increases at a given ionic strength, the magnitude of the first peak in structure factors increases and also moves to higher wavenumber values. (C) 2003 Elsevier Inc. All rights reserved.