  Stable colloidal dispersions with evenly distributed particles are important
for many technological applications. Due to Brownian motion colloidal particles
have constant collisions with each other which often lead to their aggregation
driven by the long range van der Waals attraction. As a result the colloidal
systems often tend to precipitate. A number of methods have been devised to
minimize the effect of long-range van der Waals attraction between colloidal
particles or to override the influence of the attraction in order to provide
the colloidal stability.In the PhD thesis we investigated the colloidal
stabilization in solutions of free polymers which is commonly referred to as
depletion stabilization. Previous theoretical studies of free-polymer induced
(FPI) stabilization were based on oversimplified models involving uncontrolled
approximations. Even the most basic features of the depletion stabilization
phenomenon were unknown. It was unclear how the PI repulsion depends on the
solution parameters, polymer structure and monomer/surface interactions.The
free polymer chains were modeled as random walks in a self-consistent molecular
field that satisfied to diffusion-like integro-differential equation. As the
molecular field we used the chemical potential that for semi-dilute polymer
solution can be represented as a virial expansion where we took into account
only second and third virial coefficients of the polymer solution. Varying the
parameters like polymer stiffness, polymer length, polymer concentration and
solvent regime (like theta solvent) whether it is for purely repulsive
colloidal surface, adsorbed surface or surface with grafted polymer layer we
were able to enhance the repulsive barrier due to the free polymers between the
particles and therefore found conditions for kinetic stabilization of the
system.
