Electrochemical evidences and consequences of significant differences in ions diffusion rate in polyacrylate-based ion-selective membranes

Abstract

The origin and effect of surface accumulation of primary ions within the ion-selective poly(n-butyl acrylate)-based membrane, obtained by thermal polymerization, is discussed. Using a new method, based on the relation between the shape of a potentiometric plot and preconditioning time, the diffusion of copper ions in the membrane was found to be slow (the diffusion coefficient estimated to be close to 10⁻¹¹ cm² s⁻¹), especially when compared to ion-exchanger counter ions – sodium cations diffusion (a diffusion coefficient above 10⁻⁹ cm² s⁻¹). The higher mobility of sodium ions than those of the copper–ionophore complex results in exposed ion-exchanger role leading to undesirably exposed sensitivity to sodium or potassium ions.