Conduction, in polyaniline

Arylamines display electronic properties that are favorable for materials science. In particular, arylamines are readily oxidized to the aminium form, and this leads to conductivity in polyanilines, hole-transport properties in triarylamines, stable polyradicals with low energy or ground-state, high-spin structures, and the potential to conduct electrochemical sensing. The high yields of the palladium-catalyzed formation of di- and triarylamines has allowed for ready access to these materials as both small molecules and discrete oligomeric or polymeric macromolecules. 

Bodugoz-Sentiirk, H., Giiven, O., Enhancement of conductivity in polyaniline-[poly(vinylidene chloride)-co-(vinyl acetate)] blends by irradiation. Radiation Physics and Chemistry 2011, 80,153-158. 

Min, Y.G. 1995. Determination of factors promoting increased conductivity in polyaniline, Ph.D. thesis. University of Pennsylvania. 

Electrical Conduction in Polyaniline-PMMA Blends and Their Use as Cryomagnetic Temperature Sensors [103]... 

The conductivity of poly(aniline) is 10 S/cm up to pH 4, but decreases to 10 S/cm above pH 4. The polymers are stable up to 250°C (undoped) and up to ca. 150°C (doped). Conduction in polyaniline can be accounted for in terms of electrons hopping under the assistance of proton transfer, for which the presence of water plays an essential role [107]. 

Fig. 5.14 Room temperature spin-diffusion rates, as obtained from NMR (O, ) and from ESR ( ), and conductivity in polyaniline as a function of the protonation level. (From Ref. 12.) ad is the measured conductivity, and al has been calculated from Dl, using crl = ne DllkT, with rt. the carrier concentration, proportional to y.

I. L. Hoiser, A. S. Vaughan, D. Patel, S. L. Sutton and S. G. Swingler, Morphology and electrical conductivity in polyaniline/ polyolefin blends. Transactions on Dielectrics and Electrical Insulation 8,698-704 (2001). 

V. Luthra, R. Singh, S. K. Gupta, and A. Mansingh. Mechanism of dc conduction in polyaniline doped with sulphuric acid. Current Applied Physics 3, 219-222 (2008). 

Although polyacetylene has served as an excellent prototype for understanding the chemistry and physics of electrical conductivity in organic polymers, its instabiUty in both the neutral and doped forms precludes any useful appHcation. In contrast to poly acetylene, both polyaniline and polypyrrole are significantly more stable as electrical conductors. When addressing polymer stabiUty it is necessary to know the environmental conditions to which it will be exposed these conditions can vary quite widely. For example, many of the electrode appHcations require long-term chemical and electrochemical stabihty at room temperature while the polymer is immersed in electrolyte. Aerospace appHcations, on the other hand, can have quite severe stabiHty restrictions with testing carried out at elevated temperatures and humidities. 

The monomer of the conducting polymer polyaniline is the compound aniline (aminobenzene). (a) Draw the structural formula of the aniline monomer. What is the hybridization of the N atom in (b) aniline (c) polyaniline (d) Indicate the locations of lone pairs, if any, in polyaniline, (e) Do the N atoms help to carry the current Explain your reasoning. See Box 19.1. 

In view of the complexity of the material, it is difficult to unequivocally assign a particular mechanism for electronic conduction in the polymer, although some evidence exists to suggest that it involves three-dimensional variable-range hopping as found for other polymers [213], It has also been suggested that the conductivity of polyaniline is a combination of both ionic and electronic conductivity [207], and is... 

Numerous workers126-132 have combined PB with the conducting polymer polyaniline in complementary ECDs that exhibit deep blue-to-light green electrochromism. Electrochromic compatibility is obtained by combining the colored oxidized state of the polymer1 with the blue PB, and the bleached reduced state of the polymer with PG (Equation (17)) ... 

Barsukov V., Chivikov S. The Capacitor concept of the current-producing process mechanism in polyaniline-type conducting polymers. Electrochim. Acta 1996 41 1773-79. 

As our quantum-chemical calculations show, similar transformation and delocalization of bonds takes place in the conductive forms of some other types of CPs (polyaniline, polypyrolle, etc.). Delocalization of chemical bonds after activation leads to appearance of an electronic conductivity in such types of conducting polymers and creates prerequisites for their application as electrode materials of electrochemical power sources. Such activation can be stimulated by intercalation of ions, applying the potential, and by use of some other low energetic factors. 

Transition metal compounds, such as organic macrocycles, are known to be good electrocatalysts for oxygen reduction. Furthermore, they are inactive for alcohol oxidation. Different phthalocyanines and porphyrins of iron and cobalt were thus dispersed in an electron-conducting polymer (polyaniline, polypyrrole) acting as a conducting matrix, either in the form of a tetrasulfonated counter anion or linked to... 

It must be expected that a polymer material having a much lower conductivity than polyaniline will give impedance responses revealing the effect of the three time constants obtained in the model. The system investigated was chosen for this reason since pECBZ conductivity and redox capacity [94] correspond to DE = 10 7cm2,s 1 and therefore, for the same layer thickness (500nm), the diffusion time constant would be 0.025 s. Electron diffusion should therefore be detectable in the a.c. and even in the EHD frequency domain. 

Barsukov V. and Chivikov S., The Capacitor Concept of the Current-Producing Process Mechanism in Polyaniline-Type Conducting Polymers. Electrochimica Acta, 1996 41 1773-1779. 

In an attempt to overcome the low infusible character and low solubility of aniline, dispersion polymerization of aniline was conducted in water-dispersible colloidal particles that can be cast as films or blended with other materials to prepare composites. HRP mediated polymerization of aniline in a mixture of phosphate buffer and organic solvent resulted in polyaniline composed of ortho-directed units and para-directed units. Increasing the pH or adopting an organic solvent with a high dielectric constant, enhanced the production of ortho-directed units [54]. These ortho-directed polyanilines were more thermally flexible and electrically conductive. 

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