Applications of multilayer polyelectrolyte films in corrosion inhibition, ion separation, and catalysis

Alternating adsorption of polycations and polyanions provides a very convenient means of depositing ultrathin films with controlled thicknesses and compositions. This dissertation investigates the application of these films in areas ranging from surface protection to encapsulation of nanoparticle catalysts. In corrosion reduction, deposition of multilayered poly(acrylic acid)/poly(allylamine hydrochloride) (PAA/PAH) films on Al yields ultrathin coatings that form a passivating layer on the surface oxide and increase oxide resistance by 2--3 orders of magnitude. Heating of PAA/PAH coatings produces cross-linked polyamides that have film resistances of about 5 MO cm 2, even when the film is only 10-mm thick. Although the resistance of these films is high, decreases in corrosion current due to cross-linked films still result primarily from passivation of the surface oxide, as oxide resistance is larger than film resistance.; Partial Fischer esterification of PAA allows tailoring of the hydrophobicity and charge density in multilayered PAR/derivatized PAA (d-PAA) films. The hydrophobicity of these films depends on both the extent of esterification and the nature of the derivatizing alcohol. Cross-linking of hydrophobic PAH/d-PAA films via heat-induced amidation stabilizes coatings over a wide pH range and allows base-promoted hydrolysis of the ester groups of PAH/d-PAA. After hydrolysis, films are extremely hydrophilic and selectively permeable to Ru(NH 3)63+ over Fe(CN)63- due to the high density of newly formed -COO- groups. To introduce fixed-charge density in PAA/PAH films, we also partially derivatized PAA using 2-nitrobenzyl bromide. Post-deposition UV irradiation of films formed using these photolabile polymers cleaves the 2-nitrobenzyl ester groups to yield fixed-charge sites. Such fixed charges can enhance Cl -/SO42- selectivities up to 17-fold relative to underivatized membranes. Transport simulations suggest that both Donnan exclusion and selective diffusion contribute to selectivity.; Alternating adsorption of polyethyleneimine (PEI)-metal ion complexes and polyanions also results in the formation of multilayered polyelectrolyte films, and post-deposition reduction of the metal ions in these films yields composite coatings containing metal nanoparticles. (Abstract shortened by UMI.)...