Electrooxidative polymerization monomers

Another approach uses a cobalt tetrakis(o-aminophenyl)porphyrin polymer film, prepared by electrooxidative polymerization of the monomer on top of the electrode as conductive film-mediator-couple [19]. 

Monomers 1, 2, and 4 are very insoluUe in almost all organic solvent. Thus we had to explore non-traditional solvent systems to effect our electropolymerization. 1, 2, and 4 were found to be soluble in CH2CI2 and 1,2 dichloroethane with small amounts (<5% v v) of TFA. Trifluoroacetic acid and TEA in CH2CI2 have been shown to stabilize radical cations formed during oxidation (34). Since die conductivity of this solution was low, we added 0.1 M TBAPF6, and subsequent excursions to oxidative potentials showed no clear oxidation peaks nor any products precipitating onto the electrodes. We reasoned that PFe maybe acid labile, so we synthesized triethylammonium trifluoroacetate as a supporting electrolyte and added TFA to solubilize the monomer. This solvent electrolyte system provided an excellent media for die electrooxidative polymerization of 1,2, and 4. 

After Little s proposal, many researchers have pursued such an exciting system in vain. Even metallic behavior was rarely seen in doped organic polymers, gels, and actuators. As mentioned in Sect. 3.4.4, MCso with linearly polymerized Ceo" exhibited one-dimensional (M = Rb, Cs) or three-dimensional (M = K) metallic behavior [144]. Recently a doped poly aniline was reported to exhibit a metallic temperature dependence for a crystalline polymer chemical oxidation of monomers grew crystallite polyaniline [329] early doping studies on polypyrrole (PFg) and poly(3,4-ethylene-dioxythiophene)X (X = PFg, BF4, and CF3SO3) prepared by electrooxidation at low temperatures also showed a metallic temperature dependence below 10-20 K (Scheme 16) [330, 331]. 

Conductive polymers may be synthesized via either chemical or electrochemical polymerization methods. Electrodeposition of conductive polymers from electrolytes is, thus, feasible provided that the depositing polymer is not soluble in the electrolyte.206 Conductive polymers can be deposited from the electrolytes containing the monomers via either electrooxidation or electroreduction, based on the monomer type used. Similar to that of metals, the electrodeposition of polymers is based on nucleation and growth. The deposition mechanism involves oxidation of monomers adsorbed on the electrode surface, diffusion of the oxidized monomers and oligomerization, formation of clusters, and eventually film growth.213... 

Ultrasound was also used for the dispersion of a surfactant pyrrole, prior to electrooxidation to the conducting polymer [233]. An amphiphilic (pyrrolylalkyl) ammonium monomer dispersion was used to coat the electrode surface with monomer, subsequently electropolymerized to thin films using an aqueous electrolyte for this step. Ultrasound has also been used to assist impregnation of pyrrole monomer into, for example, a conventional polymer matrix prior to polymerization to yield a composite of the conducting and conventional polymers, but is also a pretreatment effect of ultrasound rather than a sonoelectrochemical one [234],... 

Besides, ILs unit could be attached to the sidewall of CNTs by radical grafting, in which acid-oxidation pretreatment of CNTs could be avoided. Chen et al. reported that thermal-initiation free radical polymerization of the IL monomer 3-ethyl-l-vinylimidazolium tetrafluoroborate ([VEIM]BF4] on the CNT surface (Fig. 4.18a] [62]. Then under similar method, the Pt and PtRu nanoparticles with narrow size distribution (average diameter (1.3 0.4] nm for PtRu, (1.9 0.5] nm for Pt] are dispersed uniformly on the CNTs and show better performance in methanol electrooxidation than that without ILs units (Fig. 4.18b]. 

Investigations of the polymerization kinetics of aniline and its relatives (as opposed to the oxidation kinetics observed in the initial electrooxidation step) are few. Most studies reported so far are devoted to morphological aspects, nucleation [285-288], nucleation dimensionality, and related features. Preferably, electrochemical (i.e., traditional) methods of investigation were employed. The first application of proton resonance spectroscopy to the investigation of polymerization kinetics of PANI has been reported [289]. Only chemical oxidation (precipitation and dispersion polymerization) was employed the spectroscopy was used just to monitor the concentration of the monomer in the solution phase. Various oxidizing compounds of different effectiveness were studied. An investigation of the chemical oxidation with... 

Hlavaty et al. [629] electrooxidized N-vinylpyrrole and N-allylpyrrole. The former monomer yields only an electroinactive film, because of the products formed via competitive polymerization that involves the vinyl group. The latter monomer yields an electroactive polymer with properties similar to PPy according to in situ infrared spectra. 

Whereas the above strategies tend to confer a two-dimensional character on the conjugated PT backbone, the possibility of building up three-dimensional conjugated systems has been envisioned very recently. In a first attempt in this direction, tetrahedral PT precursors in which four polymerizable monomers are linked to a central silicon atom have been synthesized. While the insolubility of 69 did not allow any polymerization (A. Guy and J. Roncali, unpublished), electrooxidation of 70 leads to the deposition of a tetrakis cation radical salt that can be subsequently converted into a material containing sexithienyl units by further electrooxidation [128]. Although reported electrochemical, spectroscopic, and EDX data are in accord with the expected 3D structure, further physical characterizations are needed to definitively confirm this conclusion. 

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