Polypyrrole and Its Composites

The prindple of electroconduction in pol3q)3nrole (PPy), similar to other conjugated potymers, depends on the c arriage of electrical charge in the pofymer chain by the movement of the bipolaron (dication) and polaron (raciic al cation) produced within the backbone of the polymer by the oxidation of the chain (Figs. 7.3 and 7.4). 

Potyp3 ole was formed at a constant current until 4.5 C/ cm of current density was achieved from 0.15 M p5n-role in 0.1 M KCIO4 solution. The nanowires formed were 40-90 nm in diameter according to SEM analysis, and some of them were bridging the insulating gaps between gold electrodes. 

An X-ray photoelectron spectroscopy study has been conducted to determine the chemical composition of the synthesized nanomaterial. 

The developed sensors were tested toward different concentrations of hydrogen gas at room temperature, and their sensitivities were compared. 

1 Synthesis of Polypyrrole and PEDOT Carbon Nanofiber Composites 

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A number of new polymer composites based on conducting polymers combined with various inorganic materials have recently been described. Polypyrrole and oxide composites have been prepared by the incorporation of Fe304 particles into the CP matrix [77,151]. The oxide particles increased the corrosion protection of the films for iron in a 3% NaCl medium, apparently by increasing the oxidizing properties of the film [77] or by helping to maintain the polymer in its oxidized state [151]. 

Polypyrrole (PPy) is intrinsically conducting polymer with conjugated double bonds. PPy and its composites are used as biosensors, gas sensors, wires, micro-actuators, anti-electrostatic coatings, electrolyte capacitors, electronic devices and functional membranes, etc. [28]. PPy can be synthesized by any of the chemical techniques reported in the literature (such as change of solvent, oxidant, dopant, the ratio of oxidant to pyrrole, reaction temperature, reaction time, etc.) [29, 30]. The room temperature conductivity of PPy is of the order of 10 S/cm [31]. The preparation technique aflfects the electrical conductivity of PPy and it is reported to be enhanced up to 90 S/cm prepared by chemical oxidative polymerization method [32]. The doping of PPy with a suitable dopant such as LiF may increase its conductivity to 4.56 x 10" S/cm [33]. 

P.A. Fiorito and S.I.C. de Torresi, Hybrid nickel hexacyanoferrate/polypyrrole composite as mediator for hydrogen peroxide detection and its application in oxidase-based biosensors. J. Electroanal. Chem. 581, 31 (2005). 

The final step entailed coating both the inner and outer surfaces of the LiMn204 tubules with the conductive polymer polypyrrole [125]. It has been shown that such LiMn204/polypyrrole composite electrodes have lower resistance and higher capacity than electrodes prepared from LiMn204 alone [125]. Furthermore, the high porosity and fast (relative to... 

As a result of the advances in catalyst discovery for aqueous ethylene polymerization, silica-polyethylene nancomposites have been prepared with structures that vary with changing catalyst structure and silica composition." It is likely that many more advances in the area of high-tech composites with potential biological and nanotechnology applications will be made in the next few years through aqueous polymerization processes. In addition to free radical polymerizations and catalytic polymerizations, it should be noted that oxidative polymerizations can also be performed in aqueous media to yield conducting polymers. Recently, this has been used to prepare polypyrrole-coated latex particles that are expected to be interesting synthetic mimics for micrometeorites. 

Oxide, flouride, and polymeric films, as well as certain others, are used as protective coatings for HTSC materials (for example, see [505]). The electrodeposition of conducting polymers such as polypyrrole [433,491, 493, 506], polythiophene and its derivatives [493, 507], and polyaniline [478] is the most effective process. Anodic electropolymerization in acetonitrile solutions proceeds without any degradation of the HTSC substrate and ensures continuous and uniform coatings. Apparently, this method is promising not only for the fabrication of compositions with special properties based on HTSC [50, 28,295] as mentioned above, but also for the creation of junctions with special characteristics [507]. 

It has been shown that a pressed polypyrrole/ polycarbonate composite gives rise to microscopic conduction phenomena, and its conductivity is stable up to 200 C. Results obtained with a composite containing 20% of PPY in polycarbonate, pressed under 2000 bars up to 280°C, show that the material is still conductive (2 S/cm) and can be used as absorbing material having stable microwave properties. 

Imprinted polymers exhibiting, at the same time, electrical conductivity facilitate their assembly with an electrochemical transducer in an integrated device. In this context, the preparation of composite particles consisting of an electrically conducting polymer (polypyrrole) and an acrylic MIP should be mentioned [42]. The polypyrrole that was grown into the preformed porous MIP did not alter its recognition properties. However, in this way MIP particles could be mechanically and electrically connected to a gold-covered silica substrate. 

Karadas, N., and Ozkan, S. A. (2014). Electrochemical preparation of sodium dodecylsulfete doped over-oxidized polypyrrole/multi-walled carbon nanotube composite on glassy carbon electrode and Its application on sensitive and selective determination of anticancer drug Pemetrexed, Talanta, 119, pp. 248-254. 

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]. 

Sulfur/polypyrrole binary composite was prepared by a simple one-step ball milling method as cathode for LIB, and it was demonstrated that by making the composite with polypyrrole, the dissolution of polysulfide in the electrolyte is reduced [39]. The result of Li/S battery with S/PPy showed high initial discharge capacity of 1320 mAh/g and a stable reversible capacity of 500 mAh/g after 40 cycles. 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

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