Conductive polymer coatings

Conducting polymer is a broad concept referring to polymers with the abihty to conduct charge and ean be classified according to the assoeiated type of conductivity. When conductivity arises from ionic mobility only, the polymers are termed ion-conducting polymers. One representative system is poly(ethylene) oxide (PEO) and its interaction with salts (Doscher et al, 1951). In the case of polymeric systems with redox active species, electronic condnctivity exists and 

The corrosion behaviotrr of steel substrate coated with PANi was firstly reported by DeBerry (1985), although an earlier work by Mengoli and colleagues (1981) already refers to polymerization of PANi on iron. Since then, the majority of reported studies in this field involve the application of PPy, PTh and PANi, arrd 

12 Proton and electron transfer in PANi.The most oxidized form (pernigraniline) is not shown (Tallman etai, 2002). 

Conducting polymers exhibit unique characteristics that can be used in the context of corrosion protection. The reduction potential of conducting polymers like PPy, PTh and PANi is positive with respect to some of the most active metals like iron, zinc, aluminium and magnesium (Table 9.1). This fact can anticipate anodic protection as a relevant protection mechanism. Another point is that doping 

Conducting polymers can be prepared by chemical or electrochemical techniques. Electrochemical synthesis provides easier routes when compared with chemical synthesis and allows control over film formation, especially relevant if polymers are required as thin films deposited on the surface of metallic substrates. However, electrochemically synthesized polymers are usually more porous, a feature that requires consideration when a barrier effect is necessary. Another important aspect in the corrosion field is that the application of potential/current necessary to promote electropolymerization may accelerate dissolution (corrosion) of the metal. In some cases, an oxide pre-layer is deposited between the metal and the polymer to promote adhesion and hinder metal dissolution during the electropolymerization process (Tallman et al., 2002 Spinks et al., 2002). Alternatively, the application of layered coatings based on different conducting polymers can be a strategy to overcome the problem of metal dissolution. In the work of Lacroix et al. (2000), a layer of PPy was firstly deposited on zinc and mild steel in neutral conditions, followed by deposition of PANi in an acidic medium, because the direct deposition of PANi on those metallic substrates was not possible in an acidic medium, causing dissolution of the metal. 

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Figure 16. General transmission-line model for a conducting polymer-coated electrode. CF is the faradaic pseudo-capacitance of the polymer film, while Rt and Rt are its electronic and ionic resistance, respectively. R, is the uncompensated solution resistance.

Figure 20. Schematic diagrams of mediated electrochemistry of a solution species at a conducting polymer-coated electrode.

Collins, G.E. and Buckley, L.J. Conductive polymer-coated fabrics for chemical sensing, Synth. Met., 78, 93 (1996). 

Conducting polymers have also been prepared as coatings on both natural and synthetic fibres and fabrics. For example, silk and wool [143,144] or nylon [145] have been coated. The Milliken Corporation developed the first commercial process for producing conducting polymer coated fabrics [146]. 

Probable applications in various fields like electro chromic displays, electronic devices, modified electrodes, chemical- and bio-sensors etc. [ 133] may be envisaged. Potentially, nanodimensional oxide- (Si02, Mn02 and Zr02) based composites of these polymers have shown promise as optical materials [50]. Conducting polymer-coated low Tg latexes of sub-micron (50-500 nm) dimensions are reported to find use in antistatic and anticorrosion applications [ 113]. In the light of this information it would be of interest to explore the usability of the corresponding MMT-based composites in these directions. 

Small LL interfaces have been used by Girault and co-workers (33-38) and by Senda et al. (39, 40). We have used a small hole formed in a thin glass wall (41-43). Figure 16 shows the voltammetric response of lauryl sulfate anion transport between water and nitrobenzene. Recent analytical applications of these microinterfaces have resulted in construction of gel-solidified probes. The advantage of such a modification is ease of handling (44-47). The immobilization can be extended further to studies of frozen interfaces, or even to solid electrolytes. Significantly, ITIES theory also applies to interfaces that are encountered in ion-doped, conductive, polymer-coated electrodes. 

T. Uchikoshi, S. Furumi, T. Suzuki, and Y. Sakka. Electrophoretic deposition of alumina on conductive polymer-coated ceramic substrates. J. Ceram. Soc. Japan, 114, 55-58 (2006). 

In the development and fabrication of molecular-based electronics, it is essential to have a good understanding of the chemistry and electronic struemre of the electroactive polymer interface with other polymers, semi-conductors and metals. A better understanding of the CT interactions at the polymer/metal interface will also facilitate the application of conductive polymer coatings for metal passivation and corrosion prevention [268]. An overview of measurement methods and quantum chemical calculation techniques for smdying the chemical and electronic structure of conjugated... 

Arjsiriwat S, Tanticharoen M, Kirtikara Aoki K et al. Metal-dispersed conducting polymer-coated electrode used for oxidase based biosensor. Electrochemistry Communications 2000 2 441-444. 

Takano, N., Takeda, S. and Takeno, N. (1991) Asymmetric electrooxidation of sulfides on chiral conducting polymer coated electrode. Intern. Sympos. Organic Reactions, Kyoto, hwg. 19-21. 

Other anode systems specially developed are sprayable conductive polymer coatings, metallized zinc coatings, and conductive paints. Typical primary anode for the conductive polymer or paints is platinized niobium wire attached to the concrete prior to application. Estimated cost is 76/m with a service life of five years. 

Conducting-Polymer Coating Techniques for Usual Oxidizable... 

Nanostructured Conducting-Polymer Coatings and Anticorrosion Protection... 

R. Hasanov and S. Bilgic, Monolayer and bilayer conducting polymer coatings for corrosion protection of steel in IM H2S04 solution. Prog. Org. Coatings, 64, 435-445 (2009). 

C. K. Tan and D.J. Blackwood, Corrosion protection by multilayered conducting polymer coatings, Corros Sci., 45, 545-557 (2003)... 

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