Voltammetric Studies of Counterion Diffusion in the Monodisperse Sulfonated Polystyrene Latex

Abstract

Steady-state voltammetry for the reduction of hydrogen ion at a Pt microelectrode was carried out in an aqueous suspension of a monodisperse sulfonated polystyrene latex with hydrogen ion as counterion to the latex particles. The measured transport-limited current for the reduction of the hydrogen ion was related to the gradient-diffusion coefficient of the hydrogen ion over a wide range of concentration of inert, 1:1 electrolyte. The gradient-diffusion coefficient for hydrogen ion in the deionized, ordered latex crystal was less than 1/40th of the value found without the latex. Addition of a 100-fold excess of electrolyte (with respect to hydrogen ion concentration) resulted in a value for the gradient-diffusion coefficient close to that without the latex. A neutral molecule, 4-hydroxy-TEMPO, oxidized anodically in the suspension under these same conditions yielded transport-limited currents that were little affected by changes in salt concentration. This suggests that most of the hydrogen ions are elect...