Ion transport in a chemically prepared polypyrrole/poly(styrene-4-sulfonate) composite

The electrochemistry of a chemically prepared polypyrrole/poly(styrene-4-su lfonate) powder has been investigated by cyclic voltammetry and impedance! spectroscopy in a variety of aqueous electrolytes. The facile p-doping/undo ping of thick layers of the polymer composite is shown to be due to the hig h ionic conductivity imparted by electrolyte solution in pores. As a conseq uence, the ionic conductivities of the polymer layers are strongly dependen t on the concentration and conductivity of the electrolyte solution used bu t relatively insensitive to the doping level of the polymer. In contrast, e lectrochemically prepared polypyrrole/poly(styrene-4-sulfonate) films show much lower ionic conductivities with a pronounced dependence on doping leve l. It is concluded that layers of the chemically prepared material are appr oximately 10 times more porous than the electrochemically prepared films. H igh ionic conductivities previously obtained for polypyrrole/poly(styrene-4 -sulfonate) layers bonded to Nafion membranes have been shown to be due to HNO3 generated in pores by ion exchange of residual Fe3+ with H+ in the Naf ion.