Conductive polymer films, electrical behavior

In this paper we describe the preparation of thin polymer films by surface catalysis and anodic deposition. The results indicate that both synthesis routes produce orientationally ordered films that have similar infrared spectra. It is also shown that thin ordered films of poly(thiophene) have different electrochemical behavior than the fibrous films that are electrically conducting. 

Our experimental results suggest that the switching mechanism is not due to the formation of conductive filaments between the two metal electrodes, which was observed in a polymer film by others [31,32]. It is unlikely that filament formation is the reason for the electronic transitions in our device, since the electrical behavior of our device is strongly dependent on the structure and concentration of the gold nanoparticles. In addition, ac impedance studies, from 20 to 10 Hz (Figure 8.8), indicate that the electronic transitions in our device are different from the dielectric breakdown found in polymer films. We observed dielectric breakdown in a device with a polystyrene film sandwiched between two A1... 

An electrically conductive polymer composite of polypyrrole and poly(ethyl methacrylate) has been prepared by an emulsion polymerization procedure [ 142]. In this case, the relation between conductivity and the polypyrrole content of the composite exhibited a percolation behavior, with conductivities as high as 6-7 S/ctn. Such composites might be amenable to melt processing for coating formation. Composite films consisting of polypyrrole or poly(N-ethylaniline) filler dispersed in a polyimide matrix have been described for potential use as corrosion control coatings for the A1 alloy AA 2024-T3 [143]. 

It is also possible to modify the deposited conducting polymer in order to change its electrical, optical and other properties. For instance, polyaniline film was modified by subsequent electrodeposition of diaminomethylbenzoate (Fig. 4.6) [10,129]. As a comparison of the spectrum of PANI— where the absorbance related to the delocalized electrons at A > 600 nm is clearly apparent— with the spectrum of the modified PANI shown in Fig. 4.7 reveals, the electronically conductive parent polymer can be transformed into a redox polymer. However, the electrochemical behavior, the color [10] and the conductivity [129] of the polymer during the modification procedure can easily be regulated, and so the required properties can be finely turned [10,129]. 

Although the motion of protons does not lead to electrical conduction in the case of benzoic acid, electronic and even ionic conductivity can be found in other molecular crystals. A well-studied example of ionic conduction is a film of polyethylene oxide (PEO) which forms complex structures if one adds alkaline halides (AX). Its ionic conductivity compares with that of normal inorganic ionic conductors (log [cr (Q cm)] -2.5). Other polymers with EO-units show a similar behavior when they are doped with salts. Lithium batteries have been built with this type of... 

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