Conducting polymers film properties

Empirical kinetics are useful if they allow us to develop chemical models of interfacial reactions from which we can design experimental conditions of synthesis to obtain thick films of conducting polymers having properties tailored for specific applications. Even when those properties are electrochemical, the coated electrode has to be extracted from the solution of synthesis, rinsed, and then immersed in a new solution in which the electrochemical properties are studied. So only the polymer attached to the electrode after it is rinsed is useful for applications. Only this polymer has to be considered as the final product of the electrochemical reaction of synthesis from the point of view of polymeric applications. 

It is now 20 years since the first report on the electrochemistry of an electrode coated with a conducting polymer film.1 The thousands of subsequent papers have revealed a complex mosaic of behaviors arising from the multiple redox potentials and the large changes in conductivity and ion-exchange properties that accompany their electrochemistry. 

As illustrated in the previous sections, the electrochemical properties of conducting polymer films are strongly influenced by polymer-ion interactions. These interactions are in turn influenced by the nature of the solvent and the solvent content of the film. Consequently, the electrochemical behavior of conducting polymer films can be highly solvent dependent. Films can even become electrochemically inactive because of lack of solvation.114,197... 

Waltman, R. J. Bargon, J. Electrically conducting polymers a review of the electropolymerization reaction, of the effects of chemical structure on polymer film properties, and of applications towards technology. Canad. J. Chem. 1986, 64, 76-95... 

Given the nature of the polymer and the conduction pathway, a simple homogeneous model cannot be applied to thin conducting polymer film-electrolyte systems [27,28,31]. For thin films (< lOOnm) with pore sizes estimated to range from 1 to 4 nm, the porous surface-electrolyte interface will dominate the electrical and physical properties of the sensor. Since the oxidation of the porous surface occurs first, the interface properties play a major role in determining device response. To make use of this information for the immunosensor response, the appropriate measurement frequency must be chosen to discriminate between bulk and interface phenomena. To determine the optimum frequency to probe the interface, the admittance spectra of the conducting polymer films in the frequency range of interest are required. 

Unfortunately, even for the simplest and most studied case, the polyacetylene film, there is not a homogeneous network [5]. The mixing of the amorphous and the crystalline part makes the average properties observed, much more difficult to interpret. Not only does the very complex structure of the conducting polymer films produce scattered data for the conductivity, but the spectroscopic data are often dependent on the packing and chain conformation. As a consequence, the electronic properties of conducting polymer films may vary from one sample to another. Therefore, a major difficulty arises in deciding whether or not the difference observed was as a result of the chosen chemical structure and polymerisation route or of the way the molecules were packed. 

The response of the SAW device Is the combined result of changes In the mass loading, conductivity, or elastic properties of the surface film. Equations describing the effects of changes In these properties on the frequency of the device have been derived previously (2. )- For many sensor studies, non-conducting polymer films are employed. One equation, given below, describes Che response behavior for a SAW device coated with a thin, lossless, isotropic, non-conducting film. 

The effects of chemical structure on polymer film properties and applications were reviewed. The uses of conductive polymers in the bioanalytical sciences and in biosensor applications were investigated. Synthesis, characterization, and applications of CPs were reported, and the main aspects of CPs in chemical sensors and biosensors were covered. The advantages and limitations of conductive polymers for different biomedical applications like tissue engineering, biosensors, drug delivery, and bioactuators were reported. Different preparation methods for conductive polymers and the use of conductive pol5miers for electromagnetic interference (EMI) shielding applications were reviewed. ... 

A conductive polymer film of polypyrrole doped with polymolybdate anions was electrodeposited onto steel and found to provide corrosion protection in neutral and acidic 3.5% NaCl solution [152]. The anodic codeposition of polypyrrole and Ti02 onto mild steel in an oxalic acid medium has been described [153,154]. The PPy and Ti02 composite showed a considerable improvement in anticorrosion properties with respect to PPy films in salt spray and weight-loss tests. It was suggested that these composite films could be applied as a primary coating replacement for the phosphatized layers on mild steel [154]. 

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