Electronic and optical features of silicon carbide nanoparticles and nanocomposites
Electron paramagnetic resonance (EPR) investigations were carried out on hybrid Core-Shell nanomaterials associating silicon carbide nanoparticles and conducting polyaniline. The performed experiments compare the paramagnetic centres, the electronic transport features and the interface effects in two classes of materials, bare polymers and core-shell nanocomposites. By EPR, large doping rates were demonstrated in the bare doped polymers through important saturation phenomena which alter significantly the EPR spectrum features. Furthermore, memory effects were involved in the bare doped polymer with regard to the EPR spectrum features depending on the conditions of its thermal treatments. In the hybrid core-shell nanocomposites nor such saturation and nor memory effects were found on the EPR signals even if similar paramagnetic centres exist in both classes of samples. These behaviors were discussed taking into account the thermal stability and the doping efficiency in the considered classes of materials. Optimal doping levels were then realized and their effects on the polymers and the nanocomposites were clarified by using EPR and DRS (dielectric relaxation spectroscopy) measurements. Also, it is demonstrated that the charge carriers consist in polarons in the nanocomposites while bipolarons contributions dominate the electrical conductivity in the bare doped polymers.
Charge carrier mobility in an organic-inorganic hybrid nanocomposite
This study was supported by a NSF, DMR Solid State 
and Polymer Chemistry Grant No. DMR0075867. Partial 
support by a Defense Research Initiative on Nanotechnology 
(DURINT), Contract No. F496200110358, through the Directorate 
of Chemistry and Life Sciences of the Air Force 
Office of Scientific Research is also acknowledged.
Soluble conductive polypyrrole synthesized by in situ doping with β-naphthalene sulphonic acid
Soluble polypyrrole (PPy) with high conductivity (27 S/cm) has been prepared by chemical polymerization of pyrrol monomer in the presence of β-naphthalene sulphonic acid (NSA) as a dopant. The solubility of the resulting conducting polymer of PPy-NSA in m-cresol increases with increasing the concentration of NSA in the polymerization media, and the highest solubility of PPy-NSA in m-cresol is about 1.2 g/100 mL. The room-temperature conductivity of PPy-NSA significantly increases with the concentration of NSA when the concentration of NSA is less than 0.1 mol/L, while it slightly decreases with increasing the concentration of NSA after the concentration of NSA is higher than 0.1 mol/L. UV-VIS spectra and ESR measurements demonstrate that both polaron and bipolaron are present as a charge carrier. The resulting PPy-NSA exhibits unusual fibrillar morphology with a diameter of about 0.5 μm, which is quite different from the granular morphology of PPy doped with dodecyl benzene sulfonic acid (DBSA) and HCl. Moreover, the polymerization conditions greatly influence the morphology of the obtained PPy-NSA. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3689–3695, 1997