Organic polymers electropolymerization

With respect to the widely investigated metalloporphyrins for catalytic epoxidation, progress was made in the area of polymer-supported ruthenium porphyrins for asymmetric epoxidation. Manganese-porphyrin complexes attached via peptide linkers to organic polymers showed enhanced selectivity and catalyst stability due to donor atoms in the linker that could coordinate to the metal center. This shows that improvement can be achieved not only by optimization of the polymer or metal complex but also by appropriate choice of the linker. Furthermore, electropolymerization by anodic oxidation of suitable manganese-porphyrin complexes proved to be a promising technique for the preparation of efficient immobilized epoxidation catalysts. 

Poly(indole) has found applications as an organic polymer coating. The performance of layered semiconductors has been shown to be improved by the electropolymerization of layers of poly (indole) on the defective sites of the surface. Carbon fibers may be coated with poly(indole) by electropolymerization. More recently, poly(indole) has been employed for the polymer coating for a glucose sensor [125]. 

Recently most of the polymer studies, not only ionic but radical polymerization, too, have been carried out in organic media. However, polymer chemists engaging in electropolymeiization have come upon many difficult problems when they introduced the electrolytic processes to their own field of chemistry, because there has been little knowledge of the electrochemistry in organic media free from water. The problems were how to choose organic solvents and supporting electrolytes which would not affect the polymerization, electrodes and cells to be used in the electropolymerization. 

The counterion employed also has a marked effect on the electropolymerization process in organic solvents. For example, the polymerization of poly(methyl carboxypyrrole) (PMCP) proceeds differently in para-tolucncsul Ionic acid (pTS), tetrabutylammonium perchlorate (TBAP), tetrabutylammonium tetrafluoroborate (TBABF4), and tetrabutylammonium hexafluorophosphate (TBAPF6).63 As reported in that work, the rate of polymerization (at constant potential) and the time required for the onset of polymer deposition varied with the counterion employed. 

The derivatized monomers will influence the electropolymerization process in various ways. Differing functional groups will influence the solubility of the monomer, oligomers, and resultant polymer. For example, PPy s can be made soluble in organic solvents by alkylation at the 3-position.68 69 This influences the polymerization process because polymer may always be produced at the bare electrode (because there is no deposit). The production of soluble polymers provides a well-controlled means of polymerization. An indication of the achievable solubilities is given in Table 2.1. Although the side chain promotes solubility, the degree attainable is still dependent on the dopant incorporated and the solvent used for electropolymerization. 

G. Troch-Nagels, R. Winand and A. Weymeersch and L. Renard, Electron conducting organic coating of mild steel by electropolymerization, J. Appl. Electrochem., 1992, 22, 756 D.E. Tallman, Y. Pae and G.P. Bierwagen, Conducting polymers and corrosion Polyaniline on steel, Corrosion, 1999, 55, 779. 

Different examples of hydrogenation of organic molecules with conducting polymer modified electrodes have been described rather recently in the literature. Two different kinds of modification have been considered for this application insertion of metallic particles, and functionalization of pyrrole with transition metal complexes leading, after electropolymerization, to active electrodes. 

Owing to the intense research into PANI, one can ensure that new materials will be created in the coming months and years composites, co-polymers, (graft copolymers of PANI and nitrilic rubber [104]), PANI self-doped with organic acids, and so on. It was announced very recently that PANI electropolymerized in cam-phor.sulfonic acid (CSA) presented electrochromic properties analogous to PANI electropolymerized in common acids [105], In fact, it seems that PANl-CSA presents noteworthy stability during electrochromic cyclings [58]. 

Vinylic monomers such as acrylonitrile (AN) or methacrylonitrile (MAN) undergo an electropolymerization when submitted to electroreduction at metallic cathodes in an anhydrous organic medium [1,2], This synthesis leads to two different kinds of products (i) a physisorbed polymer which can be removed by rinsing with an appropriate solvent and (ii) a so-called grafted polymer, which is not removed with a solvent, even under sonication, and bearing carbon/metal interface chemical bonds which have been identified by X-ray Photoelectron Spectroscopy [2] and EXES [3], The former can be up to several micrometers thick, whereas the latter has a thickness which never exceeds a few hundreds Angstroms. 

---