Conductivity measurements, polyaniline

LB films prepared from poly-thiophene-3-acetic acid stearylamine or sulfonated polyaniline stearylamine polyion complexes, transferred to substrates, and doped by SbCls Absorption and infrared spectra, X-ray diffraction, and conductivity measurements Lateral d.c. conductivities of doped films were moisture dependent and were as high as 2 S cm"molecular organization consisted of randomly oriented polymers lying as extended chains parallel between the substrates and sandwiched between layers of stearylamine molecules whose chains were interdigitated 772... 

T. Shimomura, T. Akai, M. Fujimori, S. Heike, T. Hashizume, and K. Ito, Conductivity measurement of insulated molecular wire formed by molecular nanotube and polyaniline, Synth. Met., 153, 497-500 (2005). 

Polyaniline films prepared potentiostatically in sulfuric acid solution are investigated by FT-IR, UV-Vis optical spectroscopies at various dopant concentrations. Formation of charge carriers in the films are studied Ity means of electron spin resonance (ESR) spectroscopy. These results will in turn be correlated on the basis of conductivity measurement. The formations of polarons and bipolarons at different doping levels are also discussed. 

Four probe conductivity measurements on polyaniline-SWNT pellets are summarised in Figure 7.4. As observed from UV-Vis spectroscopy, reduction in Jt-conjugation defects suggests higher conductivity in snrfactant modified polyaniline. Indeed, the conductivity of PANI-1% NaDBS and PANI-1%SDS is 3.35 S/cm and 5.53 S/cm, respectively. 

While Josefowicz et al. [10] used chemically prepared PANI pellets as an electrode and for conductivity measurements, investigations of the mechanism of electrochemical oxidation also continued [11,12], and the name polyaniline was generally accepted [12], The paper of Diaz and Logan that appeared in 1980 [13] initiated research into polymer film electrodes based on polyaniline, which continues even today. 

The first electrochemical oxidation of aniline to emeraldine salt was reported by Letheby in 1862 [1] as a dark-green precipitate under aqueous acidic condition. This green powdery material soon became known as "aniline black . Almost a himdred years later interest in the electrochemistry of aniline black was revived in 1962. When Mohilner et al. [23] reported mechanistic aspects of aniline oxidations. Buvet et al. [6] studied die conductivity of prepared polyaniline and the influence of water on conductivity measurements. 

Park et al. [47] have made ambient temperature conductivity measurements of POT as a fiinction of pH and compared the results with those for other substituted polyanilines. The POT sample was doped using HCl and iodine separately. The insulator-metal transition was observed between pH 0 to 1. The iodine-doped POT sample has a conductivity of 10 S cm and the dependence of conductivity on doping concentration was not affected when the substituent was changed. This is quite different from the behaviour of protonated POT. Park et al. [47] have proposed that in the case of iodine doping, the dopants are located just outside the chain and transfer charges only so that the detailed structure of the POT is not so effective as in the case of protonation. Thus charge-transport studies confirm that electron localization is more in polytolui-dines than that of PANI due to the presence of the methyl substituent. 

For composites obtained from LCF (long carbon fibers)/PP matrix/PANl (polyaniline complex), electrical conductivity was much higher and surface resistivity much lower that in the case of separate LCF/PP and PP/PANI complex composites. By using the PANI complex, the percolation threshold of LCF composites could be moved towards a reduced fiber content. Electrical conductivity measurements over the thickness of the sample and in different directions showed a synergetic effect [136]. 

Hard materials like metals and ceramics traditionally have been used for actuators. However, soft materials with smooth movement are also useful depending on the purpose. In particular, light and smoothly fimctioning actuators are desirable as medical devices and artificial organs that have direct contact with the human body. In this section, the study of a conducting polymer, polyaniline, will be used as an example. The dependence of deformation ratio on the electrolyte solution and load will be described. Furthermore, the measurement results and the fimc-tional mechanism of excess response characteristics will also be discussed. 

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.

Polypyrrole and Polyaniline in Ni(CN)2NH3. Variable temperature electrical conductivity measurements on single crystals and pressed pellets of (V) show a... 

Electrochemical measurements on polyaniline (PANI) produce a picture of the charge storage mechanism of conducting polymers which differs fundamentally from that obtained using PTh or PPy. In the cyclic voltammetric experiment one observes at least two reversible waves in the potential range between —0.2 and -)-1.23 V vs SCE. Above -1-1.0 V the charging current tends to zero. Capacitive currents and overoxidation effects, as with PPy and PTh, do not occur The striking... 

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