Poly electroactivity

Tetra(o-aminophenyl)porphyrin, H-Co-Nl TPP, can for the purpose of electrochemical polymerization be simplistically viewed as four aniline molecules with a common porphyrin substituent, and one expects that their oxidation should form a "poly(aniline)" matrix with embedded porphyrin sites. The pattern of cyclic voltammetric oxidative ECP (1) of this functionalized metal complex is shown in Fig. 2A. The growing current-potential envelope represents accumulation of a polymer film that is electroactive and conducts electrons at the potentials needed to continuously oxidize fresh monomer that diffuses in from the bulk solution. If the film were not fully electroactive at this potential, since the film is a dense membrane barrier that prevents monomer from reaching the electrode, film growth would soon cease and the electrode would become passified. This was the case for the phenolically substituted porphyrin in Fig. 1. 

P.L. He, N.F. Hu, and G. Zhou, Assembly of electroactive layer-by-layer films of haemoglobin and poly-cationic poly(diallyldimethylammonium). Biomacromolecules 3, 139-146 (2002). 

Polyphthalamides (PPA), 10 216-217 ASTM standards for, 19 793 Poly(p-phenylene) (PPP), 22 207t 23 717 conducting, 7 523, 527 molecular structure of, 22 211 optical band gap, 7 529t room temperature conductivity, 7 532 water-soluble, electroactive, self-doped sulfonatoalkoxy-substituted, 23 720 Poly(p-phenylene benzobisoxazole) (PBO), 19 714... 

A poly (vinylchloride) membrane electrode was described for local anesthetics, based on dibenzo-24-crown-8 as the electroactive material, and di(2-ethyl)hexyl phthalate as the plasticizer [74]. It was reported that the electrode exhibited a Nemstian response to procaine, and other electrode properties were also presented. The analysis was performed at pH 6 to 6.5 vs. S.C.E., with a 0.2 M lithium acetate agar bridge. Less efficient crown ethers studied at this time were benzo-15-crown-5, dibenzo-18-crown-6, and dibenzo-30-crown-10. 

An enormous number of polymers have been used to prepare chemically modified electrodes. Some examples are given in Table 13.2 Albery and Hillman provide a more extensive list [8]. As indicated in Table 13.2, these polymers can be divided into three general categories—redox polymers, ion-exchange and coordination polymers, and electronically conductive polymers. Redox polymers are polymers that contain electroactive functionalities either within the main polymer chain or in side groups pendant to this chain. The quintessential example is poly(vinylferrocene) (Table 13.2). The ferrocene groups attached to the polymer chain are the electroactive functionality. If fer-... 

Nafion was rendered electroactive by cation exchange of a redox centre. Other polymers such as poly-4-vinylpyridine (PVP) may be protonated or quaternized to provide the possibility of introducing a redox anion such as [IrCl6]3- or [Fe(CN)6]3-.50 51 Alternatively, the pendant pyridyl groups on the neutral polymer may function as ligands and species such as [Ru(bipy)J2+ may be polymer bound. 

Large third order susceptibilities have recently been observed for trans-polyacetylene, heteroaromatic polymers, and poly[p-phenylene vinylene] (4-11). Such nonlinear phenomena in electroactive polymers due to intense laser irradiation has been linked to the photogeneration of charged solitons on time scales of the order 10 s, and values of (3w-w+w+w)—4x 10 esu for... 

In the most important series of polymers of this type, the metallotetraphenylporphyrins, a metalloporphyrin ring bears four substituted phenylene groups X, as is shown in 7.19. The metals M in the structure are typically iron, cobalt, or nickel cations, and the substituents on the phenylene groups include -NH2, -NR2, and -OH. These polymers are generally insoluble. Some have been prepared by electro-oxidative polymerizations in the form of electroactive films on electrode surfaces.79 The cobalt-metallated polymer is of particular interest since it is an electrocatalyst for the reduction of dioxygen. Films of poly(trisbipyridine)-metal complexes also have interesting electrochemical properties, in particular electrochromism and electrical conductivity.78 The closely related polymer, poly(2-vinylpyridine), also forms metal complexes, for example with copper(II) chloride.80... 

The construction and electrochemical response characteristics of poly (vinyl chloride) membrane sensors for donepezil HC1 are described. The sensing membranes incorporate ion association complexes of donepezil HC1 cation and sodium tetraphenyl borate (sensor 1), or phospho-molybdic acid (PMA) (sensor 2), or phosphotungstic acid (sensor 3) as electroactive materials. The sensors display a fast, stable, and near-Nemstian response over a relative wide donepezil HC1 concentration... 

Starburst polyacrylamines and their semiconducting complexes as potentially electroactive materials. [H. K. Hall, Jr., D. W. Polis, Polym. Bull. 1987, 77(5), 409-416] [ 604]. 

Shi et al. [70] were the first to demonstrate the use of an air and moisture stable ionic liquid, [C4mim][PF,s], for the electrochemical synthesis of poly(thiophene), grown onto a platinum working electrode by potentiodynamic, constant potential or constant current techniques. The use of growth potentials between 1.7 and 1.9 V (vs. Ag/AgCl) reportedly gave smooth, blue-green electroactive films, whereas potentials above 2 V resulted in film destruction by overoxidation. 

Endres et al. [82] have demonstrated the suitability of an air- and water-stable ionic liquid for the electropolymerization of benzene. This synthesis is normally restricted to media such as concentrated sulfuric acid, liquid SO2 or liquid HF as the solution must be completely anhydrous. The ionic liquid used, l-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, can be dried to below 3 ppm water, and this ionic liquid is also exceptionally stable, particularly in the anodic regime. Using this ionic liquid, poly(para-phenylene) was successfully deposited onto platinum as a coherent, electroactive film. Electrochemical quartz crystal microbalance techniques were also used to study the deposition and redox behavior of the polymer from this ionic liquid (Section 7.4.1) [83]. 

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