A MODEL OF GROWTH BY HETEROCOAGULATION IN SEEDED COLLOIDAL DISPERSIONS

A mathematical model for growth by hetero-coagulation in seeded colloidal dispersions incorporating electrostatic interactions, dispersion forces, and Brownian diffusion has been developed. Electrostatic effects are incorporated via an accurate numerical solution of the linearized Poisson-Boltzmann equation for the potential around two unequal spheres. Stokes-Einstein Brownian diffusivities have been calculated using exact mobility results for the two-sphere geometry. Our analysis of the complete model reveals that simpler theories based on neglect of hydrodynamic interactions are valid over a wide range of conditions encountered in hetero-coagulation. Scaling laws and "contour maps" are presented for growth rates as a function of the ratio of particle/seed diameters and of the ratio of particle size to double layer thickness. An analysis for the evolution of polydispersity is presented and it is shown that conditions in seeded systems usually favor a monodisperse size distribution. © 1990.