An emulsion process has been developed for the direct synthesis of the emeraldine salt of polyaniline (PANI) that is soluble in organic solvents. The process entails formation of emulsion particles with a mean hydrodynamic diameter of 150 nm and consisting of a water-soluble organic solvent (e.g., 2-butoxyethanol), a water-insoluble organic acid (e.g., dinonylnaphthalenesulfonic acid), aniline, and water. Aniline is protonated by the organic acid to form a salt which partitions into the organic phase. As oxidant (ammonium peroxydisulfate) is added to the reaction mixture, PANI intermediates are formed in the organic phase. As the reaction proceeds, the emulsion flocculates, forming a two-phase system. The reaction features an induction period followed by an exothermic polymerization, at which time soluble PANI forms in the organic phase. The reaction progress is conveniently monitored by temperature, pH, and open circuit potential. When dinonylnaphthalenesulfonic acid (DNNSA) is employed as the organic acid, the resulting product is highly soluble in organic solvents such as xylene and toluene (not a dispersion), has high molecular weight (M w > 22 000), and forms moderately conductive (10-5 S/cm) films. We have also found that the conductivity of PANI−DNNSA films may be enhanced (up to 5 orders of magnitude) by treating the films with surfactants such as benzyltriethylammonium chloride (BTEAC) or low-molecular-weight alcohols and ketones such as methanol and acetone. Electron microscopy shows that the conductivity enhancement phenomenon observed upon treatment with surfactants is due to self-assembly of PANI−DNNSA molecules into an interconnected network morphology. In the case of alcohol or ketone treatment the film conductivity is enhanced due to extraction of excess dopant, densification of the polymer, and a concomitant increase in crystallinity.

The reduction behavior of a Pd−Cu/γ-Al2O3 catalyst precursor (containing 2% Pd and 1% Cu) is studied by atomic scale Z-contrast imaging, electron energy-loss spectroscopy (EELS), and X-ray energy dispersive spectroscopy (EDS) techniques available in a scanning transmission electron microscope (STEM). We found that the alloying behavior of the bimetallic nanoparticles strongly depends on the reduction temperature of the catalyst precursor materials. When the precursor is reduced at 523 or 773 K, individual metallic nanoparticles are formed with a composition varying from pure metallic Pd to Pd−Cu bimetallic alloys. Detailed spectroscopic analyses of the individual nanoparticles show that Pd is preferentially segregated onto the surfaces of the bimetallic Pd−Cu nanoparticles. At higher reduction temperatures, e.g., at 1073 K, however, all the nanoparticles are found to be bimetallic Pd−Cu alloys with either Pd- or Cu-rich surfaces.

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Supported palladium (Pd) catalysts are among the most intensively studied catalyst systems for their application to many industrial processes.[1] For a full understanding of the catalytic performance of these systems, it is desirable to know the morphology, distribution, size and oxidation state of the Pd species and perhaps most importantly, whether or not any metal-support interaction (MSI) exists. Although significant research efforts have been devoted to the study of the Pd-alumina system, a full understanding of the MSI has not yet been reached. Early studies indicated g-Al 2 O 3 to be inert with Pd/g-Al 2 O 3 catalysts showing either no MSI or only a weak MSI.[2] Recent experiments, however, have shown that there exists an appreciable degree of interaction between Pd and g-Al 2 O 3 ,[3,4] which is either attributed to the formation of Pd-Al alloys or to the charge transfer between Pd and alumina.