Electrochemical Oxidative Polymerization

In the electrochemical oxidative polymerization a monomeric precursor of the conductive polymer is polymerized at an electrode. During the polymerization, ionic dopants from the electrolyte are incorporated into the polymer. For capacitor application, first, an auxiliary electrode layer has to be deposited on the surface of the insulating dielectric. Such auxiliary electrodes can be made, for example, by chemical oxidative polymerization as described in Section 

2 or by deposition of a manganese dioxide layer through pyrolysis. - For electrolytic polymerization the auxiliary electrode is contacted with an external electrode or it is connected with a bridging layer to the anode lead. 

Pol5uner built up in the porous anode body by electrolytic pol5unerization is quite difficult because of the large inner surface and tire high aspect ratio of the small pores. The current density on the outer surface of tire anode is always orders of magnitudes higher than on the inner surface. Therefore polymer growth is 

A key factor for the formation of dense outer polymer layers is the concentration of the monomer. At low concentrations the polymer formation is limited by diffusion, which results in inhomogeneous porous layers. Since the solubility of EDOT in water, which is the favored solvent for industrial applications, is very low, outer layer formation with EDOT is hindered. Sufficiently high concentrations of EDOT in water to grow a dense polymer layer can be realized by forming microemulsions through the use of surfactants. -  

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When considering the synthesis of phospholes, one has to forget most of the classical and powerful methods employed for the preparation of thiophenes and pyrroles. For example, Paal-Knorr condensation, direct ortho-lithiation, halogenation with NBS or I2/Hg2+ and Vilsmeier-Haack formylation are not operative in phosphole chemistry. Likewise, no chemical or electrochemical oxidative polymerization... 

Polypyrrole (PPy) has been studied in the form of thin films deposited on electrode surfaces, by electrochemical oxidative polymerization of pyrrole with anions (e.g. C104, HSO4 ) present in solution, resulting in relatively air-stable, highly conducting films. Chemical oxidation of pyrrole with Cu(II) or Fe(III) salts in solution has also been reported.58,59,60,61... 

PAn s are most commonly prepared through the chemical or electrochemical oxidative polymerization of the respective aniline monomers in acidic solution. However, a range of polymerization techniques has now been developed, including... 

Until relatively recently, "polyaniline", probably the oldest known synthetic organic polymer, consisted of an ill-defined class of materials, obtained by the chemical or electrochemical oxidative polymerization of aniline. Early studies were fraught with problems of uncertain compositions, and it was not until the mid-1980 s, with the advent of better characterized materials, that significant physical studies became possible. 

The polymerization is thought to proceed via cationic processes. PPP prepared by this method essentially has a linear structure and DP of about 50 this DP is comparable to that of PPP prepared via Grignard coupling. Dehydro electrochemical oxidative polymerization of benzene has also been reported. ... 

Conducting polymers are usually synthesized from the appropriate monomers by either chemical or electrochemical oxidative polymerization. Electrochemical polymerization is preferred for better penetration inside the nanopores. Polypyrrole (PPy) is one of the most important and extensively studied conducting polymers (Moreno et al. 1999 Vrkoslav et al. 2006 Lewis et al. 1997 Akundy and Iroh 2001). The deposition of PPy into PSi templates could be achieved by the electrochemical oxidation of pyrrole monomers at constant current or potential in the acetonitrile solution containing tetrabutylammonium perchlorate as supporting electrolyte. Typical potential (E-t) and current transients (i-t) recorded during the deposition of PPy into mesoporous silicon templates are shown in Fig. 3. The mechanism of polymer infiltration into the pores is of major importance in order to obtain the desired structures and control the final morphology. 

The mechanism for the electrochemical oxidative polymerization of polythiophene parallels the general mechanistic pathway outlined for the formation of polypyrrole... 

Alternative Synthetic Approaches. Most EAPs are prepared via chemical or electrochemical oxidative polymerization, precursor routes, or coupling chemistry. However, several alternative approaches have recently heen gaining attention. 

In general, the oxidative pol5mierization of phenols imdergoes a stepwise growth mechanism, although the electrochemical oxidative polymerization has been suggested to be a chain reaction mechanism (34). However, phenolic dimers... 

Scheme 14.27. a-silylated thiophenes used as monomers for chemical and electrochemical oxidative polymerization. 

Raman spectrum and photoluminescence of poly (2,5 bis (2-thienyl) 3-alkylthiophene) In this chapter the polymers are denoted pA3Th-C or pA3Th-E ( is defined in Table 14.16, C(E) refers to chemical (electrochemical) oxidative polymerization). The Raman analysis developed for polythiophene cannot be strictly applied because the Raman spectra are not identical. In particular, the R and p criteria may be redefined. However, some qualitative argimients of this analysis can be used in order to compare polymers prepared from silylated and hydrogenated monomers. 

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