Polypyrrole neutral state properties

Figure 11.19 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 perchlorate electrolyte. Additionally, the cyclic voltammogram is shown. The film has metal-like properties at positive potentials (E> OV) and neutral state properties at negative potentials (E < -0.5 V).

As illustrated previously, PT derivatives have been the focus of much research due to their unique combination of electronic properties that include electrical conductivity, electrochromism, and structural versatility. These PTs typically have a moderate bandgap, which is in the middle of the visible spectrum while others such as polyaniHnes and polypyrroles have higher bandgaps. This gives the PTs a colored appearance (most normally red) in the neutral state and they tend to become more absorbing and opaque upon oxidation (Table 20.4). 

Poly(pyrrole), known for over 50 years, is one of the most studied poly-mers. First synthesized by electrochemical polymerization in 1968, poly(pyrrole) is electrically conductive, stable, and insoluble when doped. The mechanism of its electrosynthesis was studied by Genies et Thin films of electropolymerized poly(pyrrole) (< 0.1 fim) are electroactive, and they can be switched between the neutral and the oxidized state at +0.1 V versus SCE. This particular property of polypyrrole can be applied in constructing conductivity... 

Few reports on polypyrrole-based electrochromic devices have appeared due to air instability of the neutral undoped state of the polymer. A polypyrrole-based optical window performing in water has been proposed [423]. DePaoli et al. [424] have produced a device from electrochemically deposited polypyrrole dodecylsulfonate which results in improved properties over polypyrrole doped with perchlorate. 

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