Polyaniline behavior

Banerjee S, Kumar A (2010) Dielectric behavior and charge transport in polyaniline nanofiber reinforced PMMA composites. J Phys Chem Solids 71 381... 

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]. 

Andreev, V.N., Effect of solution acidity on the electrochemical behavior of Nafion-polyaniline films, Russ. J. Electrochem., 41, 200, 2005. 

Polythiophene randomly grafted with alkyl and aniline tetramer groups (157) was synthesized. The tetramer was chosen because it is the minimum oligomer size that mimics the electrochemical behavior of polyaniline, which shows semiconduction and conduction behavior depending on its state of oxidation and the pH. Transition from one structure to the other is illustrated in equation 23, where the electron mobility of quinonoid states (158) rearranging to isolated free radicals (159) is precluded after reduction to 160. A correlation was found between the electrochemical behavior and the UVV-NIR spectra of the 157 polymers255. 

Interesting supports are the polymeric materials, notwithstanding their thermal instability at high temperatures. In the electrocatalysis field, the use of polypyrrole, polythiophene and polyaniline as heteropolyanion supports was reported [2]. The catalytically active species were introduced, in this case, via electrochemical polymerization. Hasik et al. [3] studied the behavior of polyaniline supported tungstophosphoric acid in the isopropanol decomposition reaction. The authors established that a HPA molecular dispersion can be attained via a protonation reaction. The different behavior of the supported catalysts with respect to bulk acid, namely, predominantly redox activity versus acid-base activity, was attributed to that effect. 

The polymerization potential has also been found to influence the mechanical properties of polyaniline PAn/HA emeraldine salt films.50 The most extensible films were formed at a polymerization potential of 0.65 V (versus Ag/Ag+), which displayed an extension to break of around 40%. Preparation of the PAn/HA films at 0.8 V and 1.0 V resulted in more brittle films. It was suggested that degradation of the PAn at polymerization potentials in excess of 0.8 V might explain the poor properties of the 1.0 V film. The difference in behavior of the films prepared at 0.65 V and 0.8 V was attributed to differences in their crosslink density. Unfortunately,... 

Studies performed by Yuan et al. on conductive polyaniline (PANI) nanofibers, P3DOT, and CNT thin films show that aU three are capable of forming highly compliant electrodes with fault tolerant behavior [225]. Nanowires and tubes are of particular interest since they are capable of maintaining a percolation network at large strains, thus reducing the required electrode thickness while still allowing for maximum strain performance. 

K. C. Aw, N. T. Salim, H. Peng, L. Zhang, J. Travas-Sejdic, and W. Gao, PN-junction diode behavior based on polyaniline nanotuhes field effect transistor, J. Mater. Sci.- Mater. Electron., 19, 996-999 (2008). 

S. W. Phang, M. Tadokoro, J. Watanabe, and N. Kuramoto, Microwave absorption behaviors of polyaniline nanocomposites containing Ti02 nanoparticles, Curr. Appl. Phys., 8, 391 394 (2008). 

Figure 4.21 Normalized resistance of individual electrospun HCSA-doped polyaniline nanofibers to various alcohols (a) methanol (Ct), (b) ethanol (O) snd (c) 2-propanol (A). The response of a sensor made from several nanofibers to methanol (m) is also indicated in (a) and shows lower magnitude changes when compared to the response from individual nanofibers. The inset to (a) shows the normalized resistance of a cast film of the same polymer with and without the addition of PEO. The films have a slower response time, but similar overall behavior compared to that of the nanofiber indicating that PEO has no effect on the response to methanol. (Reprinted with permission from Sensors and Actuators B., Electric response of isolated electrospun polyaniline nanofibers to vapors of aliphatic alcohols by N. J. Pinto, i. Ramos, R. Rojas eta ., 129, 621-627. Copyright (2008) Elsevier Ltd)...

A. Leone, W. Marino, and B. Scharifker, Electrodeposition and electrochemical behavior of paUadium particles at polyaniline and polypyrrole films, J. Electrochem. Soc., 139,438-443 (1992). 

Yu.M. Maksimov, E. A. Kolyadko, A.B. ShishUova, and B.I. Podlovchenko, Electrocatalytic behavior of a palladium-polyaniline system obtained by electrodepositing palladium into a preliminarily formed polyaniline film, Russ. J. Electrochem., 37, 777-781 (2001). 

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