Polypyrrole polystyrene-sulfonate electrolyte

It was mentioned that the properties of the polymer film depend on the type of anion. In Figure 11.20, another RC versus potential diagram is shown for a polypyrrole film prepared by anodic oxidation in a polystyrene-sulfonate electrolyte. The large ion cannot... 

Figure 11.20 High frequency part of capacitance and resistance of a polypyrrole film as function of the potential. The film was prepared by anodic oxidation in a polystyrene-sulfonate electrolyte. Additionally, the cyclic voltammogram is shown, whereby the film becomes electron conducting at more positive potentials (E > -0.5 V) and ion conducting at negative potentials (E < —0.8 V).

Osaka, T., Momma, T., and Nishimura, K., Electroactivity change of electropoiymer-ized polypyrrole/polystyrene-sulfonate composite film in some oiganic electrolytes, Chem. Utt., 1787-1788 (1992). 

Some applications of polypyrrole, such as drug delivery devices, require specific ion transport. Control of the ion transport process requires determination of the identity of the mobile ion, which is complicate by the fact that there are several ions present in the system. Moreover, Shimidzu and co-woiicers [138,139] demonstrated that ion transport in polypyrrole can be modified by the use of polymeric anions as dopants. Miller and Zhou [140] proved that the electrochemical switching of polypyrrole could achieve controlled release of small anions (such as CIO4), while the incorporation of an immobile polyanion (such as polystyrene sulfonate) resulted in cation transport. The polyanions become trapped within the polypyrrole matrix due to their large size and, perhaps more important, their entanglement with the polypyrrole chains. This increases the stability and mechanical strength of polypyrrole and improves electrical conductivity and electroactivity [141,142]. Therefore it has been of significant interest in the polymerization of pyrrole in polyanion electrolyte solutions [143,144]. 

The choice of an appropriate electrolyte for the doping of polypyrrole during electrochemical polymerization can improve the mechanical properties of the films obtained. Thus, polypyrrole films electrogenerated in the presence of large electrolytes, as /7-toluensulpho-nate, tosylate, benzene sulfonate, etc., yield flexible films with tensile strengths similar to polystyrene [113]. We can extrapolate this behaviour by combining the... 

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