Electrical properties of PANIS

Pourabas and Peyghambardoost [53] showed that copper filled epoxy resin composite had electrical conductivity properties. Afzal and co-workers [104] studied the electrical properties of PANI/silver nanocomposites. The silver nanoparticles in PANI reduced the charge trapping centres and increased the conducting channels of the polymer. 

Effect of Structural Morphology on the Electrical Properties of PANI Films... 

The electrical properties of PANI-CSA/PMMA blends are novel compared to those observed in more tradi-... 

C. Effect of Process Conditions on the Mechanical and Electrical Properties of PANI Base As-Spun Fibers... 

The electrical and electrochromic properties of PANi depend not only on its oxidation state but also on its protonation state, and hence the pH value of the electrolyte used. As shown in Figure 1 PANi exhibits electrochromic behavior. Electrochromic behavior of PANi is shown in Figure 9. As demonstrated, small change in the pH of the solution and/or potential could create color and conductivity changes. PANi is green in the oxidized state and is transparent yellow in the reduced states. It has violet color in very acidic and yellow brownish in very basic media [14-16]. 

Figure 4.23 (a) Typical electrical responses of PANI/PMMA composite nanofibers to TEA vapors of different concentrations (doping acid TSA). (b) Sensing magnitude of PANI/PMMA composite nanofibers with different diameters as a function of the concentration of TEA vapor. Concentration ofelectrospun PMMA solution (a) 0.32 g ml and (b) 0.18 g ml (Reprinted with permission from Sensors and Actuators B., Gas sensing properties of a composite composed ofelectrospun poly(methyl methacrylate) nanofibers and in situ polymerized polyaniline byS.Ji, Y. Li and M. Yang, 133, 644-649. Copyright (2008) Elsevier Ltd)... 

The water-soluble stabilizers at the outer surfaces of PANI nanoparticles typically include PSSA and PVA. For both cases, the resulting particles show a low diameter distribution of with a uniform spherical shape. The diameters are appropriately 40 nm with the PSSA and are varied from 100 to 150 nm for the poly(vinyl alcohol) (PVA). The electrical conductivities of the PANI nanoparticles with the use of the PSSA exceed those prepared from the PVA (Cho et al., 2004). Some modified polymerizations have been further developed to enhance the properties of PANI nanoparticles. For instance, polymerization was carried out in a thermo-stated bath with the assistance of dodecyl benzne sulfonic acid (DBSA) to produce electrical conductivities of 15 3 S cm at room temperature (Cho et al., 2004). These PANI nanoparticles were found to be particularly useful for electronic textiles (Moulton et al., 2004). 

HGURE 4.4 Electrical properties of polymer composites. (A) The electrical conductivity of the PS/graphene composite as a function of graphene volume fraction. (B) The electrical conductivity of directly mixing (DM) CNT/PANI and CNT/ PANI nanofibers with different CNT contents in the directions being parallel and perpendicular to the fiber axis. 

Roch et al. studied the TE properties of PANI/CNT composites prepared using different types of CNTs, including single-walled, multiple walled, oxidized, and xmoxidized CNTs [9]. In the series of samples studied, the PANI/unoxidized SWNTs possessed the highest electrical conductivity (530 S/m), and Seebeck coefficient (33 xV/K) and therefore highest power factor (0.6 pW/mK ). 

Also the addition of metal particles, like zinc, to CPs can lead to a beneficial effect on corrosion protection from CP coatings. Olad [53-54] found out that incorporation of zinc nanoparticles and zinc micro-size particles produces effective PANI/Zn nanocomposite and PANI/Zn composite coatings on iron, respectively. The electrical conductivity of both nanocomposite and composite systems is correlated with the zinc content, and it is higher when Zn particles are nanosized. A similar behaviour has been found in the anticorrosive properties of PANI/Zn coatings because the synergetic effect of zinc nanoparticles is more than that of micro-sized particles. 

Physical performances of the PANI nanotube have been explored in terms of electrical [300,301] and magnetic properties [302]. For example, the electrical property of a single PANI nanotube has been measured by a standard four-terminal technique. While the bulk conductivity of pelletized PANI nanotubes was as low as 3.5 x 10 S cm , the conductivity of a single PANI nanotube showed a relatively high conductivity of ca. 30.0 S cm [300]. 

The electrical conductivity properties of PANI make it probably the most frequently discussed ECP. Developments of this polymer are discussed next in date order [77-80]. 

The band structure of fully protonated emeraldine salt was studied previously by semiempirical molecular orbital (MO) calculations and more recently by ab initio calculation [41,42]. A half-filled polaron band formed via the interaction between separate polarons (there are two polarons per tetrameric repeating unit) was proposed to explain the observed optical and electrical properties of fully protonated PANI-ES. The PANI-HCSA films used in these studies were, however, cast from NMP solutions in the form of EB and then doped into the form of ES. The polymer chains in these polymer films, therefore, have the same conformational structure. 

In turn, Konyushenko et al. obtained MWCNT/PANI composites during in-situ polymerization in the presence of MWCNTs, which were uniformly coated with protonated PANI [330]. The electrical properties of nanocomposites were investigated, and similar effects as in previous work [334] were observed, i.e., the electrical conductivity increased with increased concentration of nanotubes in composite materials. The maximum conductivity, 25.4Scm was recorded for composites containing 70 wt% of MWCNTs [330]. Likewise, Wu et al. reported the increase of electrical conductivity for MWCNT/PANI composites [329]. The electrical conductivities of MWCNT/PANI composites containing 0.5 wt% functionalized MWCNTs are about 60-70% higher than of net-PANI [329]. 

Velum, J. B., K. K. Satheesh, D. C. Trivedi, M. V. Ramakrishna, and N. T. Srinivasan (2007). Electrical properties of electrospun fibers of PANI-PMMA composites. Journal of Engineered Fibers and Fabrics 2(2) 25—31. 

We have previously reported (19) the electronic and vibrational spectra, solution viscosity and electronic properties of PANI-EB and PANI-ES in HFIP solvent. We are able to correlate Ae change in hydrodynamic volume with a concomitant red shift in the UV-Vis / near IR spectra and thus verify the coil to expanded coil conformation hypothesis (20). We have also found that high quality films can be cast from HFIP that are relatively solvent free, free standing and exhibit high electrical conductivities which depends on which dopant is used. However, not matter what solvent is used, pure polyaniline films are quite brittle and lack the physical properties necessary for many applications. 

Several research groups (Mottaghitalab et al., 2006 Spinks et al., 2006 Liao et al., 2011) have recently demonstrated that the electrical and mechanical properties of PANI fibers could be reinforced by adding these fibers with CNTs. For example, Mottaghitalab et al. (2006) dispersed CNTs into the PANI/AMPSA/DCA spinning solutions and performed fiber wet spinning based on these composite solutions. Mechanical tests of the as-spun PANI fibers revealed that the addition of CNTs increased the fiber tensile strength from 170 to 255 MPa and the modulus from 3.4 to 7.3 GPa. The conductivity of the CNT-filled fibers was 716 S/cm, a 44% increment compared to the fibers without CNTs. 

Souza et al. examined the influence of plasticizers, such as dioctyl phthalate (DOP) and cashew nut shell liquid (CNSL), on the electrical properties of blends based on PANI (doped with dodecylbenzene sulfonic acid) and SBS (styrene-butadiene-styrene) copolymer [106,107]. EPR experiments revealed an increase in polaron mobility (a decrease of AHpp) as the amount of plasticizer in the blend was increased, with the effect being more pronounced for CNSL (Figure 23.25). This phenomenon is known as a second doping, and is achieved without any additional protonation of PANI rather, it is due to an enhanced conformational... 

Progress in the solution processing of high quality conducting PANI films showed that the electrical transport properties of PANI can be greatly improved by reduction of disorder [34,35]. In this section, we address the differences in transport properties between PANI-CSA processed from solution in w-cresol [27-30] and PANI doped by conventional protonic acids [65-69] such as HCI and H2SO4. 

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