Redox behavior poly

Hexacyanoferrates were immobilized on Au covered with SAM of 3,3 -thiodipropionic acid [86]. It has been found from voltammetric studies that the surface coverage of hexacyanoferrate is close to one monolayer and such an electrode exhibits very good surface redox behavior. Cheng et al. [87] have described the formation of an extremely thin multilayer film of polybasic lanthanide heteropolytungstate-molybdate complex and cationic polymer of quaternary poly(4-vinylpyridine), partially complexed with osmium bis(2,2 -bipyridine) on a gold electrode precoated with a cysteamine SAM. Consequently, adsorption of inorganic species might also be related to the properties of SAMs. This problem will be discussed in detail in a separate section later. 

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]. 

Poly(bithiophene) films from these two ionic liquids are morphologically similar (Figure 7.14), even though the redox behavior (Figure 7.9) is markedly different, suggesting that the dominant differences in the films produced are on an atomic or sub-micron rather than macroscopic level. The morphology ofthe poly (bithiophene) films appears to be similar to that described by Roncali et al. [74] who reported a thin film on the surface of the electrode, covered by a thick brittle powdery deposit, from the galvanostatic polymerization of bithiophene in acetonitrile. The nodular structures are smaller in the poly (bithiophene) films than in the poly (thiophene), which is consistent with the formation of shorter chain polymers [73], but this does not... 

Type 2 Cu2+ shows considerable variation in its redox behavior, and only recently has it been shown to undergo oxidation-reduction in a kinetically competent fashion in Poly-porous laccase. 

The redox behavior of poly(vinylferrocene) (VFc° ) has been utilized in the construction of a microelectrochemical diode along with a redox-active viologen-... 

A rather neat example of the manipulation of film electroneutrality maintenance mechanism is provided by the redox behavior of poly(xylylviologen) (PXV) films, in which the nominal counterion is poly(styrenesulfonate) (PSS). In this case, the counterion is effectively immobile, and the question arises as to whether the PXV and PSS ion charges compensate each other or are separately compensated by (other) electrolyte ions. This will clearly have implications for the possible sources and sinks of ionic charge available to satisfy electroneutrality upon PXV redox switching, and the EQCM is ideally placed to make the distinction. It was found that... 

Yamamoto, T., et al. 1997. Poly(aryleneethynylene) type polymers containing a ferrocene unit in the pi-conjugated main chain. Preparation, optical properties, redox behavior, and Mbssbauer spectroscopic analysis. Macromolecules 30 5390. 

It should be mentioned that polymers that behave in a similar way to PANl can also be prepared from compounds other than aniline (e.g., from azobenzene [201]). Substituted anilines—especially the formation and redox behavior of poly(o-tolu-idine) (POT)—have been studied in detail [328-343]. 

Poly(pyrrole-N-propionic acid) can be prepared in a single step by the hydrolysis of 3-(pyrrol-l-yl)propionitrile (Figure 5.27) [71]. In addition, it could be polymerized electrochemically in propylene carbonate using sodium perchlorate. Bartlett et al. [72] electrochemically synthesized poly(3-(pyrrolyl)-carboxylic acid) (1), poly(3-(pyrrolyl)-butanoic acid) (2) and poly(3-(pyrrolyl)-pentanoic acid) (3) in acetonitrile/LiC104 (Figure 5.28). The redox behavior of poly(3-(pyrrolyl)-carboxylic acid) (1) and poly(3-(pyrrolyl)-butanoic acid) (2) was reported to be pH dependent similar to the results of Pickup [66], and Delabouglise and... 

Physico-chemical properties of the microdomain of polymer complexes have been studied by means of Ih-NMR I, light scattering , or fluorescence polarization. Here, the authors tried to evtiluate the microdomain of polymer complexes by the electrochemical cissay. The formation of polyion complex affected the redox behavior of poly-(viologen)s considerably. Fig. 1 shows the cyclic voltammograms for PXV-PSS complex coated electrode. The first redox peak shifted to positive side, and peak broadening was observed by the complex formation. It is clear that the redox behavior was restricted by the complexation. It is known that the electron transfer process must accompany the migration of counter ions to maintain electroneutrality. As in polymer complex microdomain, polyelectrolyte chains interacted with each other and decreased their free volume, they should thereby provide the domain with smaller porosity. 

The foregoing paragraphs were concerned with the description of the redox behavior of the conducting polymers, but nothing was said about the influence of chemical substituents in the parent monomer and their influence on the redox activity. In fact, these have a considerable influence and a substantial amount of work has been done on this aspect. The main effect of the substituents is to disrupt the degree of conjugation in the polymer and thus decrease its conductivity. This in turn reduces the redox activity. For example, poly(yV-methylpolypyrrole) shows very reduced redox activity and poor electronic conductivity. 

The use of poly(aniline) as a battery electrode on account of its redox and proton transfer behavior was described in 1968 [110,111]. In 1986 poly(aniline) was presented as a novel conducting polymer its preparation and redox behavior were described [112 114]. The phenomena of anodic oxidation and discharge by means of reversed polarity have been known since 1891 [3]. 

However, changes in the structure and the geometry of the polymer chains can also modify the redox behavior of the polymer to the same extent. From UV-visible absorption spectroscopy complementary data, Roncali et al. suggested that the complexation of Li+ by the polyether side chains increased simultaneously the coplanarity of the conjugated backbone and the rigidity of the polymer framework [241, 242]. Nevertheless, the ionic effect observed with poly(4) in the solid state could be considered to be weak because of the slight bathochromic shift of the absorption maximum of the polymer (about 10 nm). 

The influence of alkali cations such as Na, U, and K on the redox behavior of poty(13a) and poty(13b) has been analyzed from multisweep cyclic voltammetry erqreriments. The electrochemical response of poty(13b) was found to be unaffected by the presence of alkali cations. In contrast, a large shift of the oxidation peak of poly(13a) toward more positive potentials was observed in the presence of Na. Upon the cationic complexation, the electron density contributed by the otygen atoms of the crown ether to the conjugated potymer backbone was decreased, and consequently, the oxidation potential of the polymer was enhanced. 

Kiya Y, Hutchison GR, Henderson JC et al (2006) Elucidation of the redox behavior of 2,5-dimercapto-l,3,4-thiadiazole (DMcT) at poly(3,4-ethylenedioxythiophene) (PEDOT)-modified electrodes and application of the DMcT-PEDOT composite cathodes to lithium/lithium ion batteries. Langmuir 22(25) 10554—10563... 

In a novel approach to controlled chemical release using CPs, rather than incorporating the chemical to be released as the dopant in the CP according to the standard method, Kossmehl [726(a)] used the redox behavior of a CP, poly (thiophene), to electrochemically modulate the wettability of the polymer surface. When used in the form of tiny dots on an ink transfer cylinder, the CP could be made hydrophilic (doped) or hydrophobic (de-doped), thereby respectively picking up or not picking up ink particles. The printed image could thus be continuously changed electrochemically. 

Yamamoto T, Etori H (1995) Poly(anthraquinone)s having a jc-cmain chain. Synthesis by organometallic polycondensation, redox behavior, and optical properties. Macromolecules 28 3371-3379... 

Tang YJ, Zeng XQ (2008) Poly(vinyl ferrocene) redox behavior in ionic liquids. J Electrochem... 

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