Electropolymerization kinetics

The electropolymerization kinetics have been studied by a few groups of investigators Beck et al. [78], Otero et al. [79], and Park et al. [73]. Beck et al. reported that the reaction limited current density, shows... 

The electropolymerization kinetics of 3,6-dimethylthieno[3,2-6]thiophene was studied by cyclic voltammetry, chronoamperometry and chronopotentiometry on glassy carbon in the presence of a 0.1 M LiC104 solution (2001JAE839). 

This means that we can follow the empirical kinetics of the electropolymerization process, at a constant overpotential (Fig. 6), by tracking the weight of the rinsed and dried polymer film,37 41 as we do in homogeneous polymerization processes of conducting or nonconducting poly-... 

The final conclusion from the different kinetic studies that simultaneously followed productivity, consumed current, storage capacity of the obtained films, and the current efficiency in generating electroactive polymer in the final film is that any electropolymerization of conducting polymers occurs together a partial degradation of the electroactive polymer. The final film is a mixed material. From the kinetic studies we know the variables that increase or deplete the degradation reaction in relation to the polymerization reaction. 

The final conclusion of this short discussion is that electropolymerization is a fast method (a film of about 5 //mean be obtained by polarization in 1 rnin) that uses a complex mechanism (Fig. 12) in which electropolymerization, cross linking, degradation, and chemical polymerization can coexist to produce a mixed material with a cross-linked and electroactive part and a passive fraction.67-71 However, ifwe control the variables acting on the kinetics of the different simultaneous reactions, the complexity also provides flexibility, allowing us to obtain materials tailored for specific applications. 

A remarkable recent example of the influence of electropolymerization temperature on the properties of PAn products is observed in the potentiostatic polymerization of aniline in the presence of chiral (+)-HCSA to give optically active PAn/(+)-HCSA films. The CD spectra of the polymers electrodeposited at < 25°C were inverted compared to the spectra of analogous emeraldine salts deposited at > 40°C, indicating an inversion of the preferred helical hand for PAn chains.38 The observations may be rationalized in terms of a temperature-induced interconversion between two initially (kinetically) formed diastereomeric PAn products. 

B. D. Curtis, C. J. Dubois, D. L. Electrochemical Reduction of CO2 Catalyzed by a Dinuclear Palladium Cooperativity OrganometalUcs 1995, 14, 4937. (k) Ogata, T. Yanagida, S. Brunschwig, B. S. Fujita, E. Mechanistic and Kinetic-Studies of Cobalt Macrocycles in a Photochemical CO2 Reduction System - Evidence of C0-CO2 Adducts as Intermediates /. Am. Chem. Soc. 1995,117, 6708. (1) Arana, C. Keshavarz, M. Potts, K. T. Abruna, H. D. Electrocatalytic Reduction of CO2 and 0-2 with Electropolymerized Films of Vinyl-Terpyridine Complexes of Fe, Ni and Co Inorg. Chim. Acta 1994, 225, 285. 

Electropolymerization Reaction Mechanism, Influence of Additives, Kinetic Considerations and Influence on the Related Polymers... 

But the most smdied electropolymerizable porphyrins are the tetra-amino-and tetrahydroxyphenyl-substituted ones. Indeed, both of them were developed to elaborate electrodes having potentiometric responses to several kinds of anions, such as iodide for example . Co(II) tetrakis(p-hydroxyphenyl)porphyrin 53-based films were used for the elaboration of potentiometric and fibre optic pH sensors with minimal interferences from anions. Zn(II)-53-based films were also used and characterized for kinetics studies of hydrogen evolution at their surface . Zn(II)-53 as well as Pd(II)-53 and free base tetra(4-methyl pyridinium) porphyrin (H2-54) were electropolymerized on indium tin oxide substrates, leading thus to starting materials for the making of donor/acceptor... 

Moreover, the combination of SPR and an electrochemical allows for in situ kinetic investigation, a doping-dedoping process, and optical property changes during electropolymerization of electroactive monomers and has also been recently used in immunosensor applications [45, 49-52]... 

We have shown that pyrrole can be electropolymerized on various oxidizable metals such as iron, mild steel, aluminum, copper, tin and zinc, and that this can be achieved in one or two steps. During our investigations, the strategy adopted was to circumvent the unfavorable thermodynamic data by the optimization of kinetic conditions. To this end, we have developed various processes, in which the metal is initially passivated with respect to corrosion... 

Das, I., Agrawal, N.R., Gupta, S.K., Gupta, S.K., Rastogi, R.P. Fractal growth kinetic and electric potential oscillations during electropolymerization of pyrrole. J. Phys. Chem. A 113, 5296 (2009)... 

For the electropolymerization of aniline it is necessary to include a protonation step, as the polymer is protonated in the acid medium employed [13]. The foregoing mechanism shows that the growth of the polymer can be influenced by the kinetics of any of the steps in the process. Consider the cyclic voltammogram for the electrodeposition of polycarbazole shown in Fig. 1. Initially, the charge transfer controls the kinetics. After the first peak due to the oxidation of the carbazole monomer, a shoulder or hump may also be discerned at more positive potentials. This is the signature of a nucleation step. 

In reality, there is no absolute proof in favour of either of these mechanisms, but it appears to be generally agreed that cationic coupling is the most important mechanism for the formation of poly(/ -phenylene). It must be emphasized that in the case of the electropolymerization of pyrole and thiophene, which are electropolymerized in much the same way as benzene, the radical-cationic coupling mechanism was proven from kinetic results deduced from ultra-fast cyclic voltammetry experiments [153]. Isotopic studies... 

Electrical kinetics From the chronoamperograms obtained during each electropolymerization, the con-... 

From kinetic studies we have experimental evidence to accept the coexistence of several processes during pyrrole electropolymerization. The relative rate of the different reactions, and thus the final composition and properties of the electrogenerated polypyrroles, will depend on the chosen parameters of synthesis. The reverse reasoning always is true and fundamental from a technological point of view defining a property, conditions of synthesis can be selected in order to optimize it. 

Reaction 4 attempts to recover the considerable influence of electrolytes in empirical kinetics, through its discharge on the polymer. The formed radical is immediately transferred to a monomer molecule. This indirect initiation can explain the behaviour of pyrrole electropolymerization at high potentials in water [51]. The other electrolyte influences act on the metal oxide production [49], by stabilization of the monomeric radical cations [130] and through polymer oxidation. 

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