The courses of aniline oxidation with ammonium peroxydisulfate in aqueous solutions of strong (sulfuric) and in weak (acetic) acids, followed by temperature and acidity changes, are different. In solutions of sulfuric acid, granular polyaniline (PANI) was produced; in solutions of acetic acid, PANI nanotubes were obtained. The external diameter of the nanotubes was 100-300 nm, the internal cavity 20-100 nm, and the length extended to several micrometres. The morphology of PANI, granular or tubular, depends on the acidity conditions during the reaction rather than on the chemical nature of the acid. PANI nanotubes were also produced when aniline was oxidized in the absence of any acid. The bulk conductivity of PANI prepared in solutions of acetic acid was 0.08-0.27 S cm −1 , depending on the acid concentration. Protonated PANI prepared in sulfuric and acetic acids were deprotonated with ammonium hydroxide to obtain PANI bases and the ammonium salt of the protonating acid. FTIR spectroscopy showed the differences in the molecular structure of the PANI bases. Irrespective of whether the polymerization was performed in solutions of sulfuric or acetic acid, PANI had hydrogen sulfate counter-ions only. The PANI morphology is thus not controlled by the nature of counter-ions. The acidity of the reaction medium determines the protonation of monomer, oligomer and polymer species. The chemistry of aniline oxidation is likely to be affected especially by the protonation of an intermediate in the pernigraniline form. It is proposed that, in the course of aniline oxidation, pH-dependent self-assembly of aniline oligomers predetermines the final PANI morphology.

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Polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in the presence of methyl orange. They were subsequently used for the reduction of silver ions to silver nanoparticles. The nanotubular form of polypyrrole is compared with the classical globular morphology in its ability to reduce silver ions. Both polypyrrole salts and bases were used in the experiments. The content of metallic silver in the resulting composite, determined by thermogravimetric analysis, was 21-31 wt%.Elemental composition is also discussed on the basis of energy-dispersive X-ray spectroscopy. Contrary to the expectation, the conductivity of polypyrrole nanotubes in salt form, 35.7 S cm À1 , was reduced to 20.9 S cm À1 after the incorporation of silver. The presence of silver had generally little effect on the conductivity. The temperature dependence of conductivity reveals that the composites maintain the semiconducting character of polypyrrole and their conductivity increased with increasing temperature. The conductivity of the composites surprisingly increased when the samples were placed in vacuo.

Pure hydride of the α-UH type without any β-UH admixture was prepared by high-pressure hydrogenation of U stabilized by Zr. Such material, characterized by a general formula (UH) Zr , is stable in air at ambient and elevated temperatures. H release is observed between 400-450 °C similar to β-UH. Its stability allowed to measure magnetic properties, specific heat, and electrical resistivity in a wide temperature range. Despite rather different crystal structure and inter-U spacing, the electronic properties are almost identical to β-UH. Its ferromagnetic ground state with Curie temperature ≈ 180 K (weakly and non-monotonously dependent on Zr concentration) and U moments of 1.0 μ indicate why mixtures of α- and β-UH exhibited only one transition. Magnetic ordering leads to a large spontaneous magnetostriction = 3.210, which can be explained by the increase of the spin moment between the paramagnetic (Disordered Local Moment) and the ferromagnetic state. The role of orbital moments in magnetism is indicated by fully relativistic electronic structure calculations.

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