Coating of multiwalled carbon nanotubes with polymer nanospheres through microemulsion polymerization.

We report a simple and noncovalent method for coating multiwalled carbon nanotubes (MWCNTs) with polyaniline (PANI) nanospheres using a microemulsion polymerization method. In this method, aniline polymerization is performed with MWCNTs in the presence of sodium dodecyl sulfate (SDS), which serves as both a surfactant and a dopant. Morphological, structural, thermal, and electrical properties of MWCNT-PANI nanocomposites were analyzed. The TEM results of the nanocomposites prepared with surfactant reveal that 30-50-nm-diameter PANI nanospheres were coated on the surface of the MWCNTs. Composites prepared without surfactant were found to be in core-sheath-type cable structures. The conductivities of the nanocomposites synthesized through microemulsion polymerization were found to be one order of magnitude higher than both the conductivities of pure PANI and the composites prepared via in situ chemical polymerization without an assisting SDS surfactant. The mechanism for the formation of nanostructured composites is presented.

Synthesis of electrically conductive and superparamagnetic monodispersed iron oxide-conjugated polymer composite nanoparticles by in situ chemical oxidative polymerization.

Core-shell nanocomposites composed of iron oxide (Fe3O4) nanoparticles and conjugated polymer, poly(3, 4-ethylenedioxythiophene) (PEDOT), were successfully synthesized from a simple and inexpensive in situ chemical oxidative polymerization of EDOT with Fe3O4 nanoparticles in the micellar solution of lignosulfonic acid (LSA) which serves as both a surfactant and a dopant. These nanocomposites (Fe3O4-PEDOT) were subsequently characterized for morphological, crystalline, structural, electrical and magnetic properties by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), four-probe meter and superconductor quantum interference device (SQUID), respectively. Results show that the nanocomposites have a spherical core-shell shape, are approximately 10 nm in size and are superparamagnetic with good magnetic saturation and good electrical conductivities. Existence of Fe3O4 in the nanocomposites was confirmed by using Energy dispersive X-ray photoelectron spectroscopy (EDAX) and X-ray photoelectron microscopy (XPS). We also investigated a possible formation mechanism of the core-shell nanocomposites, and the effect of Fe3O4 nanoparticles on the electro-magnetic properties of the nanocomposites. Such novel conducting and superparamagnetic composite nanomaterials can be applied to sensors, magnetic data storage, electro-magnetic resonance wave absorption, etc.