Polyelectrolyte adsorption and self-assembly on charged surfaces

Polyelectrolyte adsorption on charged surfaces is of fundamental importance in materials science and biology. Thermodynamic models based on electrostatics and statistical mechanics have been developed in this dissertation to study polyelectrolyte adsorptions. The chemical potentials of the surface components are equated to their counterparts in the bulk solution by minimizing the free energy. This method enables us to self-consistently analyze polyelectrolyte adsorption including interactions neglected by Poisson-Boltzmann approach and equivalent mean field models.; Nanopatterns induced by polyelectrolytes adsorption onto oppositely charged surfaces are analyzed. The nanopattern size passes through a maximum upon salt concentration increase. The adsorption is shown to depend on polyelectrolyte effective charge density after ion condensation along polyelectrolytes. We extend the model to analyze surface induced micellization of hydrophobic-charged block copolymers at copolymer bulk concentrations below the critical micelle concentration. Systems with strong charge groups and systems with weak charge groups are considered. The effects of surface charge density, polyelectrolyte block line charge density, surface tension of the hydrophobic block, and degrees of polymerization of the blocks on the surface induced micellization are studied. The addition of salt may increase the critical micelle concentration. The monomer excluded volume has significant effect on systems with weak charge groups.; The mechanism of polynucleotide adsorption to like-charged surfaces in divalent salt solution is studied including the pH effect on the surface charge density and the interactions between divalent ions and surface groups. The adsorption is driven by the cooperative effect of divalent ion condensation along polynucleotides and their reaction with the surface groups. Calculated divalent salt concentration and pH value variations on polynucleotide adsorption are consistent with atomic force microscope results. Long-period X-ray standing waves is employed to study the adsorption of mercurated-polyuridylic acid in a ZnCl2 solution onto a negatively charged hydroxyl-terminated silica surface. These in situ measurements, which simultaneously reveal the Hg and Zn distribution profiles, are in good agreement with our model. The model also shows that polyelectrolyte surface density increases with the divalent ion reaction constant and the polyelectrolyte line charge density, but decreases after the addition of monovalent salt.