Polyaniline camphor sulfonic acid -doped

Fig. 1. (a) Comparison of normalised electrical conductivity of individual MWCNTs (Langer 96 [17], Ebbesen [18]) and bundles of MWCNTs (Langer 94 [19], Song [20]). (b) Temperature dependence of resistivity of different forms (ropes and mats) of SWCNTs [21], and chemically doped conducting polymers, PAc (FeClj-doped polyacetylene [22]) and PAni (camphor sulfonic acid-doped polyaniline [2. ]) [24]. 

Hydrochloric acid as well as camphor sulfonic acid doped polyaniline prepared in chloroform often have [59] log a proportional to T as expected for quasi-one-dimensional variable range hopping, Equations (3) and (4). Generally, the higher conductivity samples have a weaker temperature dependence at low temperatures (Tq 700-1000 K for T<80 K), and lower conductivity samples a stronger temperature dependence (To 4000 K). The smaller Tq for the more highly conducting samples has been associated with weaker localization due to improved intrachain and interchain order. 

Figure 8 Thickness dependence of total shielding efficiency (SET) of highly conducting polymers (A) stretched heavily iodine doped Tsukamoto polyacetylene, (B) camphor sulfonic acid doped polyaniline cast from m-cresol solvent, (C) PFg doped polypyrrole.

Wang, Y.Z., J. Joo, C.-H. Hsu, and A.J. Epstein. 1995. Charge transport of camphor sulfonic acid-doped polyaniline and poly(o-toluidine) fibers Role of processing. Synth Met 68 207. 

Hydrochloric acid as well as camphor sulfonic acid doped polyaniline prepared in chloroform often have log a proportional to as expected for quasi-one-dimensional variable range hopping (VRH), Fig. 46.11, [73,121,143] ... 

Hosier et at (2001) [25] prepared 2% (w/v) solutions of dodecylben-zene sulfonic acid doped polyaniline and PE separately in hot xylene. Appropriate volumes of the two solutions were then mixed and further refluxed to ensrue complete dissolution of the polymers. Finally, the blend solution was poured into cold acetone and the PE/polyaniline blends were precipitated as a green solid. Pereira da Silva et at (2001) [26,27] obtained PE/polyaniline blends by casting a mixture of hot solutions of camphor-sulfonic acid doped polyanihne in m-cresol and PE in decalin onto glass substrates. Melt blending usually involves dispersing the infusible ICPs into melt thermoplastic matrices [28]. Due to the insolubility of PE, as well... 

It is also interesting to note that polyaniline doped with camphor sulfonic acid (PANl-CSA) was intercalated into M0O3. This was achieved by adding PANI-CSA dissolved in m-cresol to an aqueous sol of LixMo03- The stoichiometry of the intercalate as determined from elemental analysis was (PANI-CSAo.i24)i 06M0O3. Evidence of intercalation was obtained from powder X-ray diffraction [59]. 

Figure 2. Inter-relationships between viscosity of polyaniline doped with d,l camphor sulfonic acid in solutions of cholorform and m-cresol of increasing m-cresol content and electronic spectra, conductivity, dielectric constant and x-ray diffraction spectra of free-standing films (cast from the 3.0 wt.% solutions of the composition indicated). Viscosity studies and spun films for Vis/UV studies employed 0.33 wt.% solutlons,24 25.

The importance of crystallinity as a factor in promoting high conductivity is well exemplified by the fact that replacement of the camphor sulfonic acid anion in the doped polymer with chloride ion by simple exchange in aqueous HCl results in considerable retention of crystallinity and the attainment of a conductivity of =44 S/cm — a conductivity for HCl-doped polyaniline film, approximately an order of magnitude higher than any previously reported conductivity for non-oriented HCl-doped film, . 

We have prepared a series of nylon / poly aniline blends using the solvent hexafluoroisdpropanol (HFIP), which is an excellent solvent for polyaniline emeraldine base (PANI-EB), polyaniline doped with various sulfonic acids (PANI-ES) and for hi molecular weight nylon 6 and nylon 12. It was observed that conductivity and morphology of the blends varied with the compatibility of the sulfonic acid anion with the nylon. Methanesulfonic acid, butane sulfonic acid dodecylbenzene sulfonic acid and camphor sulfonic acid were used as PANI dopants and the PANI-ES / nylon blends were characterized by electrical conductivity (room and low temperature) and transmission electron microscopy. The results of these various measurements and the conclusions which can be drawn regarding morphology and conductivity of Ihe blends, will be reported. 

Doping Doped polyaniline solutions were prepared in HFIP by a solution doping method (22). Solutions turned from blue / brown to forest green, characteristic of doped polyaniline. Molar doping of undoped polyaniline is calculated for polyaniline emeraldine salt from the mole ratio y = (moles of dopant) / (moles of phenyl-NH), determined by elemental analysis. Optimally doped polyaniline has the value of y = 0.5. Dopants used were camphor sulfonic acid (HSCA), (Aldrich) methane sulfonic acid (HMSA), Aldrich and dodecyl benzene sulfonic acid (HDBSA), TCI America. Nylon 6 and 12 (Aldrich) were vacuum dried before solution blending. All PANI-ES solutions were filtered with a 0.50 pm filter. 

Polyanilines have been processed fi om solutions of neutral polyaniline in NMP, DMPU and others for some time[l,2]. Significant strides have been made in making fibers form these solutions. None eless, the technique suffers fi om the disadvantage that processed articles are non-conductive and need to be doped in a secondary step. The technique is not suited for preparation of coatings on a commercial scale. Processability of polyaniline in the doped form is more attractive as it removes the subsequent doping step. Functionalized protonic acids such as camphor sulfonic acid, preferably in the presence of m-cresol and dodecyl... 

Polyaniline Blends. Polyaniline doped with camphor sulfonic acid, PANI-CSA, in the form of a blend with poly(methyl methacrylate), PMMA, is also used as hole injection material in PPV-based LEDs owing to the low barrier for hole injection [209,210] and the match of the PPV electroluminescent emission with the transmittance window of the PANI-CSA/PMMA blend (Fig. 10). Blends of polyester resin (PES) with PANI-CSA were also used for this purpose [209]. The barrier height for hole injection at the PANI-CSA-PES/MEH-PPV blend was found to be dependent on the PANI-CSA concentration, ranging from about 0.02 eV at a concentration of 5% w/w to about 0.1 eV for pure PANI [209]. In the case of PANI-CSA-PMMA/PPV interfaces, the barrier height for hole... 

Polyblend fiber composites of polyaniline, doped with dodecylbenzene-sulfonic acid, and PE exhibited a conductivity of 2 S cm with 40 wt % polyaniline composition, but the percolation threshold was 10%. Hoiser et al. (2001) also obtained polyaniline/ PE blends with conductivities in the range lO " to lO " S cm and a percolation threshold of 10% [45]. Blends of polyaniline doped with camphor sulfonic acid and ultra high molecular weight PE displayed a percolation threshold of 5% with the conductivity being about 10 S cm [47]. The conductivity of extruded polyaniline/ PE blends increased from 3.38 x 10" to 1.19 x lO " S cm as the polyaniline varied from 5 to 20 wt % [23]. No percolation threshold was observed up to 20 wt % loading as the polyaniline used to prepare the blends was not doped by any added acids, as had been the case in other studies. 

Previously, the enhancement of the device performance in ITO/polyaniline/MEH-PPV/Ca devices has also been observed (9). The metallic emeraldine salt form of PANI is prepared by doping and complexation with functionalized sulfonic acids (e.g. camphor sulphonic acid, CSA), yielding a conducting PANI-complex soluble in common organic solvents. Hence, based on the results obtained from our research, we conclude that the enhancement of the device performance in ITO/PANI/MEH-PPV/Ca devices is probably due to the fact that the CSA dopes the surface of MEH-PPV and subsequently eidiances the charge injection and lowers the device operating voltage. 

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