Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) were prepared through the oxidative polymerization of a mixture of aniline, 2,5‐diaminobenzene sulfonic acid, and MWCNTs. Fe, Pd, or Fe–Pd alloy nanoparticles were embedded into the MWCNT–SPAN matrix by the reduction of Fe, Pd, or a mixture of Fe and Pd ions with γ radiation. Sulfonic acid groups and the emeraldine form of backbone units in SPAN served as the source for the reduction of the metal ions in the presence of γ radiation. The existence of metallic/alloy particles in the MWCNT–SPAN matrix was further ascertained through characterization by high‐resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis, and conductivity measurements. HRTEM pictures clearly revealed the existence of Fe, Pd, and Fe–Pd nanoparticles of various sizes in the MWCNT–SPAN matrices. There were changes in the electronic properties of the MWCNT–SPAN–M composites due to the interaction between the metal nanoparticles and MWCNT–SPAN. Metal‐nanoparticle‐loaded MWCNT–SPAN composites (MWCNT–SPAN–M; M = Fe, Pd, or Fe–Pd alloy) showed better thermal stability than the pristine polymers. The conductivity of the MWCNT–SPAN–M composites was approximately 1.5 S cm−1, which was much higher than that of SPAN (2.46 × 10−4 S cm−1). Metal/alloy‐nanoparticle‐embedded, MWCNT‐based composite materials are expected to find applications in molecular electronics and other fields. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3355–3364, 2006
We synthesized nanotubular poly(diphenylamine) (PDPA) by confining PDPA in the channels of MCM-41 (with a possibility of tuning the pore size). A two-stage synthesis, comprised of adsorption of diphenylamine (DPA) in the channels of MCM and subsequent oxidative polymerization to form PDPA, was employed. Adsorption of monomer was done in two different media, sulfuric acid (SA) and β-naphthalene sulfonic acid (NSA). DPA molecules form self-assembly with NSA inside the pores of MCM-41. Polymerization proceeds differently in these two selected media. NSA provides an environment for the formation nanotubular PDPA inside the pores of MCM-41. Results from nitrogen adsorption−desorption measurements, X-ray diffraction analysis, scanning electron microscopy, FTIR spectroscopy, and thermogravimetric analysis show the presence of PDPA in the channels of MCM-41. PDPA formed inside the pores of MCM-41 was also removed from the pores. Field emission transmission microscopy of PDPA extracted from the pores reveals the nanotubular morphology. FTIR spectroscopy, proton NMR spectroscopy, and conductivity measurement were used to characterize the nanotubular PDPA. The electronic state of nanotubular PDPA shows the confinement effect from MCM-41 that is different from PDPA formed by the conventional method.
ABSTRACT:Core-shell type sulfonated polyaniline (SPAN)-iron oxide nanoparticles (IONP) composites (IONP-SPAN-NC) were prepared. The interactions between the positve and negative charges on the surface of IONP and sulfonic acid and amine groups, respectively, in SPAN form the basis for core-shell structure for the composite. Sulfonated polyaniline hollow spheres (SPAN-HS) were generated by preferential dissolution of IONP from the composite. TEM photograph of IONP-SPAN-NC reveals that IONPs are 'glued' to SPAN chains and hollow spheres are formed on removal of IONP. Morphology, optical and magnetic properties of the IONP-SPAN-NC and SPAN-HS were compared. [DOI 10.1295/polymj.38.349] KEY WORDS Sulfonated Polyaniline / Iron Oxide / Nanoparticles / Composite / Hollow Sphere / Polyaniline (PANI) and its derivatives are considered as potential materials for optical, micro and nanoelectronic applications such as light emitting diodes, photovoltaic devices, chemical sensors, actuators, drug delivery and energy storage devices, [1][2][3][4][5] due to their advantageous properties. The oxidation state and extent of doping are the key factors that determine the electrochemical properties of polyaniline class of materials. Doping can be achieved externally with acids like HCl or HClO 4 or internally (self-doping). In sulfonated polyaniline (SPAN), self-doping occurs through interaction between -NH group of PANI and sulfonic acid group present in the phenyl rings. SPAN has stable and reproducible electrical properties, pH independent electrical conductivity, processing ability and higher thermal stability than PANI. 6,7 Applications of conducting polymers in nanodevices require the use of one dimensional (1D) nanostructures and thus synthesis of nanoscale conducting polymers (nanotubes/-rods/-wires/-fibers) has attracted considerable attention.8 1-D PANI nanostructures have been generated by chemical and electrochemical methods through polymerization of the monomer with the aid of either a 'hard' or a ''soft'' template. Examples of hard templates include zeolite channels, track-etched polycarbonate, and anodized alumina. 9,10Soft templates, such as surfactants, micelles, liquid crystals, thiolated cyclodextrins and polyacids, 11,12 have been reported to be capable of directing the growth of polyaniline 1-D nanostructures with diameters smaller than 100 nm. Physical methods, 13,14 including electrospinning and mechanical stretching have also been used to make polyaniline nanofibers. Studies have been reported on blending of PANI with inorganic nanoparticles to result PANI based hybrid nanostructures. 15,16 Formation of conducting polymer nanotube inside the channels of MCM-41 (mesoporous silica) has been recently reported. 17,18 Capsules and hollow spheres have wider applications in catalysis, delivery and controlled release, opto-electronics, microcavity resonance and photonic crystals. 19 Colloidal particles have been used as templates for the preparation of hollow nanospheres. 20-22Layer-by-layer assembly of polymeric or...
Composites were prepared by incorporating magnetite (Fe3O4) nanoparticles into the matrix of a sulfonated polyaniline (SPAN) [poly(aniline‐co‐8‐amino‐2‐naphthalenesulfonic acid) PANSA] through chemical oxidative polymerization of a mixture of aniline and 8‐amino‐2‐naphthalenesulfonic acid in the presence of magnetite nanoparticles. The composite, magnetite/SPAN(PANSA) was characterized by means of transmission electron microscopy (TEM), X‐ray diffraction (XRD), elemental analysis (EA), Fourier transform infrared (FT‐IR) spectra, UV‐vis spectroscopy, thermogravimetric analysis (TGA), conductivity and magnetic properties measurements. TEM image shows that magnetite nanoparticles were finely distributed into the SPAN matrix. XRD pattern of the nanocomposite reveals the presence of additional crystalline order through the appearance of a sharp peak at ∼43° and 71°. Conductivity of the nanocomposite (0.23 S/cm) is much higher than pristine copolymer (1.97 × 10−2 S/cm). The results of FT‐IR and UV‐visible spectroscopy reveal the presence of molecular level interactions between SO 3− groups in SPAN and magnetite nanoparticles in the composite. Copyright © 2006 John Wiley & Sons, Ltd.
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