Abstract:

The main thread-line connecting the different parts of this dissertation is various non-double layer interactions present in the colloidal system.

The first chapter is a general introduction to the double layer and non-double layer interactions.

In chapter 2 and 3, the double layer and hydration interactions have been coupled into a single set of equations because both are dependent on the polarization of the water molecules. The coupled equations involve the electric fields generated by the surface charge and surface dipoles, as well as the field due to the neighboring dipoles in water. The obtained equations were employed to explain the restabilization observed experimentally at large ionic strengths for colloidal particles on which protein molecules were adsorbed.

In chapter 4, a general expression for the force generated between the two charged plates immersed in an electrolyte solution containing relatively small charged particles was derived based on Langmuir's approach. For charged plates immersed in a solution of an electrolyte and charged small particles, the effects of particle charge, particle charge sign, particle size and volume fraction of the particles on the force acting between the two plates were examined. In chapter 5, a cell model was proposed to examine the behavior of a dispersion of large particles immersed in an electrolyte solution containing small particles.

In chapter 6, two-dimensional Poisson-Boltzmann equation was solved to calculate the double layer interactions between two plates grafted polyelectrolyte. In chapter 7, a lower dielectric constant in the polymer adsorption layer is suggested The hairy adsorption layer can have a long range effect on the repulsive double layer interactions.

In chapter 8, the bridging force induced by polyelectrolyte was investigated by using a self-consistent-field approach which takes into account the van der Waals interactions between the segments of the polyelectrolyte molecules and the plates, as well as the electrostatic and volume exclusion interactions. A positive contribution to the force between two plates is generated by the van der Waals interactions between the segments and the plates.