Concentration-dependence of faradaic currents and conductivity in a polystyrene sulfonic latex suspension

The conductivity, κ, in a suspension of polystyrene sulfonic latex without supporting electrolyte showed a linear dependence on the volume fraction, vf, of the latex for vf<0.03 with a finite intercept. In contrast, this deviated upward from the linear line for vf>0.03. These variations were qualitatively consistent with the dependence of the voltammetric reduction current of H+ on vf without supporting electrolyte. The current values were only a few percent of the theoretical diffusion-controlled current that could be observed in the suspension with supporting electrolyte. This fact indicates the electrostatic immobilization of the hydrogen ions by sulfonic latex particles. A plot of the current against κ at common values of vf showed that the current for vf>0.07 was smaller than the value predicted from the conductivity. This can be explained in terms of a combination of the increase in electrostatically unbounded H+ estimated by conductance measurements and electric migration in which the electrochemical depletion of [H+] also causes the depletion of the latex.