Electropolymerization electrochemical electrochemistry

These facts are different demonstrations of the same event degradation reactions occur simultaneously with electropolymerization.49-59 These reactions had also been called overoxidation in the literature. The concept is well established in polymer science and consists of those reactions between the pristine polymer and the ambient that promote a deterioration of the original polymeric properties. The electrochemical consequence of a strong degradation is a passivation of the film through a decrease in the electrical conductivity that allows a lower current flow at the same potential than the pristine and nondegraded polymer film did. Passivation is also a well-established concept in the electrochemistry of oxide films or electropainting. 

Metal nanoparticles housed in zeolites and aluminosilicates can be regarded as arrays of microelectrodes placed in a solid electrolyte having shape and size selectivity. Remarkably, the chemical and electrochemical reactivity of metal nanoparticles differ from those displayed by bulk metals and are modulated by the high ionic strength environment and shape and size restrictions imposed by the host framework. In the other extreme end of the existing possibilities, polymeric structures can be part of the porous materials from electropolymerization procedures as is the case of polyanilines incorporated to microporous materials. The electrochemistry of these types of materials, which will be termed, sensu lato, hybrid materials, will be discussed in Chapter 8. 

Sasso S V, Pierce R J, Walla R and Yacynych A M 1990 Electropolymerized 1,2-diaminobenzene as a means to prevent interferences and fouling and to stabilize immobilized enzyme in electrochemical biosensors A aA Chem. 62 1111-7 Gerhardt G A, Oke A F, Nagy G, Moghaddam B and Adams R N 1984 Naflon-coated electrodes with high selectivity for CNS electrochemistry Brain Res. 290 390-5... 

In contrast to the area of redox protein electrochemistry, redox enzyme electrochemistry has received much greater attention, driven in many cases by the desire to construct practical, self-contained enzyme electrodes for commercial applications. Redox enzyme electrochemistry is also easier to study in many ways because the substrate or product is often detected electrochemically rather than the enzyme itself. Various types of electroactive polymers have been used with redox enzymes, including redox polymers, redox-active hydrogels, and electropolymer-ized films of conducting and nonconducting, polymers. We discuss each type of polymer in turn, starting with electropolymerized films. 

Usually the functional moiety is covalently linked to the conjugated backbone, but it can be sometimes added to ECP as a dopant when it is under an ionic form e.g., sulfonated P-cyclodextrins have been successfiilly incorporated in one step as anionic dopants in PPy by electropolymerization [230]. In some cases, electrochemistry can be combined to chemical reactions to derive functional ECPs functional PANI materials can be obtained from the reduction of the emeraldine form by alkylthiols [255] and the functionality degree on the PANI backbone can be monitored by successive oxidation-reduction cycles various functionalized PANIs can also be synthesized through electrophilic substitution or nucleophilic addition reactions [256]. For example. Figure 18.10 shows the similar electrochemical behaviors of sulfonated PANI made from reduction of emeraldine by sulfite salt followed by reoxidation, compared to thin films deposited from solution of highly sulfonated PANIs. 

Naoi K, Outa Y, Maeda M, Nakamura S (1995) Electrochemistry of surfactant-doped polypyrrole film(l) formation of columnar structure by electropolymerization. J Electrochem Soc 142 417 22... 

Whenever vinyl monomers are electropolymerized, two situations must be distinguished depending on whether the vinyl monomer is the precursor of the initiating species or not. Either the polymerization is directly initiated by the activated monomer or the initiation is indirect whenever the active species (radical, anion, or cation) is generated by a compound other than the monomer (conducting salt, solvent, or properly selected additives). Besides these electroinitiated polymerization processes, a very recent report also demonstrated that electrochemistry is a valuable tool to mediate atom transfer radical polymerization (ATRP). Indeed, an externally applied electrochemical potential can activate the copper catalyst by a one-electron reduction of an irutially added air-stable cupric species (Cu /ligand) allowing... 

Electrochemical polymerization offers particular advantages in that polymerized porphyrins can form electroactive, adherent and stable films on solid electrodes. Oxidative electropolymerization of several porphyrins and metalloporphyrins have been reported . Special focus has been placed on amino-substituted porphyrins due to the propensity of aniline to form electroactive polymers. Murray et al. reported on the electropolymerization of tetrakis(o-aminophenyl)porphyrin and several para-, ortho-, and meta-substituted tetrakis(aminophenyl)porphyrins with Co as a central metal s. They found that poly-Co(o-NH2)TPP films are effective catalysts for the electroreduction of oxygen in aqueous solution. Metalloporphyrin films on solid electrodes have been mainly characterized by voltammetry and resonsance Raman spectroscopy. The electrochemistry of ruthenium paradiethylamino substituted tetraphenylporphyrins recently have been investigated . This study reports the ac impedance and UV-visible reflectance spectroscopic studies of paradiethylamino substituted tetra-phenylporphyrin films formed via an oxidative electropolymerization process. 

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