Colloidal forces in the presence of polymers and surfactants

The first part of this work involved examination of a polymer, polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock copolymer, expected to impart steric stabilization. The surface concentrations and layer thicknesses of the PS-PEO diblock copolymers were found to be indistinguishable from PEO homopolymer. They attained low surface concentrations and the adsorbed layer thicknesses were much smaller than the unperturbed radius of gyration. The diblocks do not form the expected highly extended polymer brushes. No evidence of enhanced stability due to steric stabilization by the PS-PEO was observed. The lack of brush formation was most likely the result of the large, soluble EO block providing a kinetic barrier that prevented the PS-PEO chains from forming an end-anchored brush.; The second portion of this work dealt with understanding adsorption, coadsorption and the effects on colloidal forces for single-component solutions and mixtures of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and the cationic polyelectrolyte polylysine. Scanning angle reflectometry was used to examine adsorption while total internal reflection microscopy (TIRM) measured colloidal forces. The adsorption of CTAB to silicon oxide from water occurs via a surface-limited process and is greatly affected by the CTAB bulk concentration and the ionic strength of the solution. At low bulk CTAB concentrations and low ionic strength, the adsorption process is very slow, requiring {dollar}sim{dollar}17 hrs to reach the adsorption plateau. In high bulk CTAB concentrations and high ionic strength solutions, the adsorption process reaches its plateau in a matter of several minutes. Polylysine adsorbed irreversibly from solution and yielded moderate surface concentrations (0.2-0.4 mg/m{dollar}sp2{dollar}). For the coadsorption case, the CTAB and polylysine coadsorb from a mixture to form mixed adsorbed surface layers. This occurs in spite of the mutually repulsive nature of the similarly charged species. The total surface concentration and composition of the mixed layer is dependent on the ionic strength of the solution. The coadsorption process was also found to be controlled by non-equilibrium effects.; The adsorption of CTAB and polylysine alters colloidal forces by changing the interfacial charge density. The adsorption of CTAB and polylysine from their single-component solutions and from mixtures results in charge reversal on glass surfaces. This results in changes to the electrostatic double-layer repulsion.; The presence of dissolved polylysine results in a depletion attraction between a colloidal sphere and a flat wall. The depletion attraction increases with increasing polyelectrolyte concentration and decreasing background electrolyte. The magnitude of the interaction was found to scale with the osmotic pressure of the polyelectrolyte solution. While the magnitude of the interaction scaled with osmotic pressure, the range of the depletion interaction was dependent on the size of the molecule as well as the electrostatic interactions between the polyelectrolyte and the surfaces. (Abstract shortened by UMI.)...