Materials Literature
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Abstract The chemical synthesis of polypyrrole in water, with FeCl 3 as an oxidant of pyrrole, was investigated. During these experiments in ambient air, a large evaporation of pyrrole was observed. Moreover, a kinetic study of pyrrole disappearance by high‐performance liquid chromatography (HPLC), with various FeCl 3…
Polycrystalline pyridinium perchlorate has been studied over a wide range of temperatures by differential thermal analysis, proton NMR spectra and relaxation, and dielectric permittivity measurements. Two solid-solid phase transitions at 232 and 248 K have been revealed and the pyridinium cation reorientations in all…
Highly localized, laser-excited optical modes of silver colloid fractal clusters were observed using photon scanning tunneling microscopy. The spatial distribution of the modes shows the frequency and polarization selectivity suggested by numerical simulations. The results verify the main concepts of the recently deve…
We investigate interactions between interfacial disequilibrium and compositional convection during the freezing of an alloy from below to form a mushy layer. A theoretical model is developed in which a stagnant mushy layer underlies a melt that is convecting vigorously, driven by compositional gradients associated wit…
An x-ray surface forces apparatus for simultaneously measuring forces and structures of confined complex fluids under static and flow conditions is described. This apparatus, combined with an intense synchrotron x-ray source, allows investigation of molecular orientations within a thin liquid crystal film confined bet…
The quinoxaline and phenazine dianions can each be stabilized by two lanthanocene units, which leads to the novel binuclear rare-earth complexes with short LaC and LaN contacts. These La–ligand contacts resemble those in “aromatic alkali-metal amides”. The phenazine complex is shown on the right.
Very flexible and antiaromatic versus relatively rigid and aromatic—that is the difference between [24]porphyrinogen 1 and its oxidation product [22]porphyrin dication 2. Although both compounds occur in the cis, trans, cis, trans configuration, the protons along the inner perimeter of 2 are shifted roughly 20.5 ppm u…
An energetically low-lying octet ground state and ferromagnetic exchange interactions between seven CuII ions characterize the magnetic behavior of the complex cation in 1, whose novel Cu7(OH)8 framework is shown on the right, bpym = 2,2′-bypyrimidine.
One equivalent of Ca2+ and Sr2+ ions induces the isomerization of the colorless spirobenzopyrans 1a (n = 1) and 1b (n = 2), respectively, to the colored merocyanines 2. Compounds of type 1 thus function as ion-selective chemical sensors.
Im Kampf um die Aromatizität gewinnt Benzol gegen [18]Annulen: Das erste voll durchkonjugierte, Benzol enthaltende Porphyrinanalogon 1 erweist sich als nicht‐18 π‐aromatisch, nur das Tautomer mit intakten benzoiden Aren wird beobachtet. 1 läßt sich in ca. 6% Ausbeute aus der entsprechenden Tripyrrandicarbonsäure und I…
In PbHfO3 single crystals the amplitude of the thermal vibrations for Pb ions in the high-temperature Pm3m phase, calculated from the Debye-Waller factor, reached unexpectedly large values. The random displacements of Pb ions were assumed and the new thermal vibration amplitude, which is more reasonable from the cryst…
The microstructure of epitaxial La0.5Sr0.5CoO3(LSCO)/ferroelectric lanthanum modified lead zirconate titanate (PLZT)/ La0.5Sr0.5CoO3(LSCO)/bismuth titanate(BT)/yttria-stabilized zirconia (YSZ) heterostructures on [001] silicon has been investigated. X-ray diffraction and pole figure analysis reveal epitaxial growth of…
A theory for highly anisotropic hydrogen-bonding molecules in the nematic and isotropic phases is presented. The theory is applied to a very simple molecular model: a hard spherocylinder which is able to form a dimer with another such molecule. In the dimer the two molecules are constrained to be positioned end-to-end…
The electrical band gap of porous silicon is determined from measurements of the reverse bias current of homojunction pn porous silicon diodes versus temperature, resulting in a value of 2.2 eV. This value is in good agreement with the value of 1.97 eV obtained from photo- and electroluminescence experiments.
Abstract The compatibility of blends of polyamide‐6/[styrene‐(ethylene‐butylene)‐styrene] triblock copolymer (SEBS) was enhanced with a compatibilizer, maleated SEBS, whose compositions were varied from 0 to 4 wt % of the blends. The maleated SEBS (MA‐g‐SEBS) was synthesized by reacting (grafting) maleic anhydride (MA…
A combination of scaled particle theory for fluids and a simple cell model for crystalline solids is used to study the freezing behaviour of a binary hard-sphere system. As the two kinds of sphere become increasing dissimilar, we find that the phase diagram changes from a spindle type to an azeotropic type, and then t…
Surface temperature images obtained by the ratioing of visible (5)D(2) and (5)D(1), emissions from a La(2)O(2)S:Eu phosphor coating are demonstrated. The visible phosphor emissions permit imaging with standard CCD cameras. Temperature resolution to 1 K is achieved over a temperature range of 193-293 K.
Abstract The degree of crystallinity and the disorder parameter in ramie fibers treated with various concentrations of aqueous NaOH solutions at room temperature (∼ 30°C) and at 0°C, respectively, have been analyzed by the wide‐angle x‐ray diffraction method of Ruland and Vonk. 9–11 The results appear to suggest the p…
Optimization was carried out for the recovery of microbiol poly(3-hydroxybutyrate) (PHB) from Alcaligenes eutrophus. This process involved the use of a dispersion made of sodium hypochlorite solution and chloroform. The dispersion enabled us to take advantage of both differential digestion by hypochlorite and solvent…
Photodiodes fabricated from conjugated polymers exhibit excellent sensitivity to visible-UV radiation. The photosensitivity increases with reverse bias voltage. The photoresponse of diodes fabricated from poly(3-octyl thiophene) is relatively flat in the visible and near UV; for wavelengths shorter than 550 nm, the ab…