A study of the interfacial behavior of polyoxyethylene at a mercury—aqueous solution interface: Compact and diffuse layers

Abstract

The adsorption of polyoxyethylene (POE) at a mercury-solution interface has been studied, using NaF, KF, and KCl as supporting electrolytes and polymers over a molecular weight range from 400 to 4000. In the first part, a flat configuration of the adsorbed macromolecule is put forward from an analysis of data concerning three characteristic properties of the adsorbed layer. In the second part, information on the diffuse layer in the presence of a saturated layer of POE is obtained from experiments at various salt concentrations. While the classical models of Gouy-Chapman (GC) and Stern-Grahame for the diffuse and global double layer are well verified for concentrations higher than 10 −2 M, a deviation from the theoretical expectation is found for more dilute solutions, increasing with the absolute value of the surface charge. It seems difficult to interpret this effect in terms of an artifact due to the experimental techniques or to solution impurities. Similar deviations from the GC model are expected in the case of electrophoretic measurements. A comprehensive explanation is not given but the results show that it is related to the particular nature of the double layer in the presence of polymer.