Phenols electropolymerization

Electropolymerization is also an attractive method for the preparation of modified electrodes. In this case it is necessary that the forming film is conductive or permeable for supporting electrolyte and substrates. Film formation of nonelectroactive polymers can proceed until diffusion of electroactive species to the electrode surface becomes negligible. Thus, a variety of nonconducting thin films have been obtained by electrochemical oxidation of aromatic phenols and amines Some of these polymers have ligand properties and can be made electroactive by subsequent inincorporation of transition metal ions... 

Polymer films can also be electropolymerized directly onto the electrode surface. For example, Abruna et al. have shown that vinylpyridine and vinyl-bipyridine complexes of various metal ions can be electropolymerized to yield polymer films on the electrode surface that contain the electroactive metal complex (see Table 13.2) [27]. The electronically conductive polymers (Table 13.2) can also be electrosynthesized from the corresponding monomer. Again, a polymer film that coats the electrode surface is obtained [25]. Electropolymerized films have also been obtained from styrenic, phenolic, and vinyl monomers. 

MWCNTs were functionalized with iron phthalocyanines (FePc) to improve the sensitivity towards hydrogen peroxide. A highly sensitive glucose sensor with an FePc-MWCNT electrode based on the immobilization of GOx on poly(o-amino-phenol) (POAP)-electropolymerized electrode surface [219]. A hemin-modified MWCNT electrode to be used as a novel 02 sensor was obtained by adsorption of hemin at MWCNTs and the electrochemical properties of the electrode were characterized by cyclic voltammetry [220]. 

Such size-exclusion film is prepared by electropolymerizing polyphenol in the presence of the phenol monomer. 

The use of MPc complexes as electrocatalysts for the detection of analytes relies on the formation of modified electrodes. Thiol, alkylthio, or arylthio substituted MPc complexes readily form self-assembled monolayers (SAMs) on gold. Amino substituted MPc complexes can easily be electropolymerized onto electrodes. Direct adsorption of the monomer onto electrodes (especially carbon electrodes) also occurs. The modified electrodes are then employed for detection of analytes ranging from neurotransmitters, thiols, phenols, and other biologically and environmentally important molecules. 

A number of desirable properties were exhibited in this work, which include ease of monomer synthesis, mild positive electropolymerization potential, polymer stability to continuous potential cycling, and stability to storage under ambient conditions. Unfortunately, the nature of the polymer backbone could not be definitely assigned. Nevertheless, the utility of pendant phenol and aniline groups for anchoring metal complexes to an electrode surface is a method worth further investigation. 

Electropolymerization. One coating method consists in the oxidative electropolymerization onto the surface of the electrode. Films of poly(oxy-phenylene) were initially deposited from a 1 1 (by volume) water methanol solution containing 0.25 M 2-allylphenol, 0.2 M 2-butoxyethanol, and 0.4 M ammonium hydroxide or allylamine by biasing the wires at a constant voltage of 4 volts for half an hour (50). Under these conditions the phenolic groups of the monomers are oxidized, generating a free radical, which ini-... 

Electropolymerization and Properties of Films Formed from Phenolic and Tyrosine Monomers... 

Fig. 7 Schematic of the tyrosine and phenolic monomers studied, DELT and DEDT self-assembly, and the adsorption vs electropolymerization processes occurring at the Pt electrode surface. For simplicity, we have not attempted to indicate the - 0-ether linkage products that may also represent a minor fraction of the linkages foimd in the electropolymerized phenolic film products. This figure was reprinted with permission from [71]...

A capacitive sensor with a molecularly imprinted polymer film as a sensitive layer has been reported. The layer was prepared by electropolymerization of phenol on a gold electrode with the template molecule, phenylalanine. The sensor capacitance was decreased by the addition of phenylalanine, but there was almost no change with glycine, tryptophan and phenol. The response time was 15 min (time for a half of the stationary value, 60 min), and the dynamic range was given as 0.5 to... 

Rhodes, C.P., J.W. Long, and D.R. Rohson, Direct electrodeposition of nanoscale solidpoly-mer electrolytes via electropolymerization of sulfonated phenols. Electrochemical and Solid State Letters, 2005. 8(11) pp. A579-A584... 

All electrochemically stable metal complexes that are substituted by pyrrole, thiophene, aromatic amino, aromatic phenol and some other groups such as vinyl, are suitable for anodic electropolymerizations from solution (organic solvent or water) in the presence of a conducting salt (counter ions in the oxidized films). 

The electropolymerization technique, applied to oxidizable monomers (phenols and their derivatives) and developed in the seventies to obtain homogeneous thin dielectric fdms [2], was extended to heterocyclic conducting polymers as early as 1979 with polypyrrole (PPy) [3], and some time later to poly aniline (PANI, 1981) [4,5] and poly thiophene (PT, 1982) [6]. It was shown that adherent homogeneous conductive sohd... 

A recent method of preparing a very thin molecularly imprinted film on a QCM is the electropolymerization of phenols and aromatic amines [42]. The preparation... 

In an early approach towards MIP-based sensors using capacitance measurement, thin MIP membranes were prepared by in situ polymerization of MAA/ EDMA and then sandwiched as a sensing layer in afield effect device a capacitance decrease was observed due to specific binding of the template L-phenylalanine anilide [103]. Recently, two promising alternative approaches towards ultrathin MIP films for capacitive sensors had been reported electropolymerization of phenol for imprinting of phenylalanine [74], and photo-initiated graft copolymerization of AMPS/MBAA for imprinting of desmetryn [82] and creatinine [83] (cf Sections III.C.2, III.C.3). 

Conductometric sensors measure the change in conductivity of a selective layer in contact with two electrodes upon its interaction with the analyte. Conductometric sensors are often based on field-effect devices. For example, capacitance sensors such as the above-mentioned field-effect capacitor [5] belong to this group. Capacitive detection was also employed in conjunction with imprinted electropolymerized polyphenol layers on gold electrodes [36]. The sensitive layer was prepared by electropolymerization of phenol on the electrode in the presence of the template phenylalanine. The insulating properties of the polymer layer were studied by electrochemical impedance spectroscopy. Electrical leakages through the polymer layer... 

Electropolymerization of phenols proceeds similarly to that for pyrrole poly(phenol) itself is probably a mixture of para- and meta-linked units. Films are generally continuous and free from such defects as pinholes. They have been used for corrosion protection, as permselective films, " and as pH sensors. Like poly(pyrrole) films, electropolymerized phenol films have a number of features that make them attractive for immobilizing an enzyme. First these films can be grown under electrochemical control from aqueous buffered solution at neutral pH. Second a wide variety of phenol derivatives are available that allow some control over the films physical characteristics. Third these films are permselective, which could be useful in preventing interfering species from reaching the... 

Sasso et used electropolymerized films of 1,2-diaminobenzene, a monomer that produces films with properties very similar to those of the phenols, to... 

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