9727717 Schlenoff Interface-Induced Polyelectrolyte Structures Interfaces are known to assist in the formation of novel and useful polyelectrolyte structures. These include polymer brushes, whcih are employed in stabilizing emulsions and dispersions. A brush is produced when a polymer with a surface- seeking end group or block is exposed to a solid-liquid or liquid- solid interface. Typical brush-forming macromolecules include polyelectrolyte diblock copolymers, where a short hydrophobic block drives the polymer to the surface from aqueous solution. Since the hydrophilic, brush-forming segment of the molecules is a polyelectrolyte, the conformation of the brush will be a strong function of the nature and concentration of the counterion. Since brushes will be exposed to a variety of ions when they are applied to stabilizing dispersions, it is essential to determine the effect of these ions on brush adsorption. Focusing in particular on the liquid/liquid interface - rarely studied yet quite pervasive - brushes will be produced here using radiolabeled polyelectrolytes. The label permits accurate in situ determination of the amount of polymer adsorbed to the interface. Using a suite of recently-developed radiometric techniques, the surface coverage will be evaluated in the presence of monovalent and divalent counterions, as well as other charged polymers. Questions of a fundamental nature that will be addressed include whether the polymer is adsorbed in the thermodynamically reversible, or irreversible (kinetic limited) mode. This project will also focus on ultrathin polymer films made from the layer-by-layer deposition of alternately charged polyelectrolytes. These newly-discovered polyelectrolyte structures are straightforward to prepare and have potential applications as thin film conductors, light-emitting layers and bioactive (enzyme-containing) thin films. The mechanism by which charge is balanced and distributed within these films is not underst ood. In the proposed work, the charge within the multilayer films will be probed using radiolabeled counterions. Conditions for producing multilayers with a range of counterion concentrations will be established using novel electrochemically active polyelectrolytes as building blocks. These polyviologens will be synthesized by a new method and will be tested for application as electrochromic and electrocatalytic thin films. %%% This project will enhance our understanding of polyelectrolyte multilayers, thin films, and interfaces, which have important implications to colloids, adhesion, lubrication, and surface science. ***
