Electrochemical Characterization of Polyelectrolyte Multilayers Deposited at Liquid−Liquid Interfaces

Abstract

The deposition of polyelectrolyte multilayers at an aqueous solution−organic gel interface by layer by layer deposition of anionic poly(sodium 4-styrenesulfonate) and cationic poly(allylamine hydrochloride) is described. With suitable electrolytes and electrodes in both phases, alternating current voltammetry is employed to measure the capacitance of the polyelectrolyte multilayer as a function of the number and type of layers deposited. The charge distribution across the interface is investigated by analyzing the capacitance measurements based on a theoretical model that describes the potential profile across the multilayer at the interface between the two electrolyte solutions. Subsequently, cyclic voltammetry is used to probe the transfer of cationic tetraethylammonium and the cationic Alzheimer drug 9-amino-1,2,3,4-tetrahydroacridine (tacrine) across the polyelectrolyte multilayer. The effective transfer rate constant is reduced by the presence of the multilayer film, and the lower rate observed for a polycation- compared with a polyanion-terminated multilayer is interpreted in terms of the theoretical model.