Thermal decomposition kinetics of polypyrrole and its star shaped copolymer

Thermal behavior of 2,4,6-tris(4-(1H-pyrrol-1-yl)phenoxy)-1,3,5-triazine monomer, polypyrrole, and their star shaped copolymer, were investigated using TG and DTA methods. It was found that Tria melts at 517 K and after than it starts to decompose. Decomposition proceeded in two stages which were corresponding to removal of branched groups and remaining core structure degradation, respectively. Polypyrrole and copolymer showed similar thermal behaviors. These compounds decomposed in three stages which are removal of solvent, removal of dopant anion and rest of structure decomposition. The calculation of activation energies of all reactions were realized using model-free (KAS and FWO) methods. The graphs were prepared which show the alteration of activation energy with decomposition ratio. Thermal analysis results showed that dopant anion and solvent removal activation energy values for copolymer are lower than polypyrrole. Star shaped loose-packed novel structure greatly facilitates solvent and dopant anion removal from copolymer. It can be concluded also that thermal analysis can be used as predict package structure of conducting polymers.     

Synthesis,Structures, and Properties of Fused Thiophenes for Organic Field‐Effect Transistors

A series of fused thiophenes composed of fused α‐oligothiophene units as building blocks, end‐capped with either styrene or 1‐pentyl‐4‐vinylbenzene groups, has been synthesized through Stille coupling reactions. The compounds have been fully characterized by means of ¹H NMR spectrometry, high‐resolution mass spectrometry, and elemental analysis. The molecules present a trans–trans configuration between their double bonds, which has been verified and confirmed by Fourier‐transform infrared spectroscopy and single‐crystal X‐ray diffraction analysis. The X‐ray crystal structures showed π–π overlap and sulfur–sulfur interactions between the adjacent molecules. The decomposition temperatures were all found to be above 300 °C, indicating that compounds of this series possess excellent thermal stability. The fact that no phase transition occurs at low temperature indicates that they should be well‐suited for application in devices. Moreover, they possess low HOMO energy levels, based on cyclic voltammetry measurements, and suitable energy gaps, as determined from their thin‐film UV/Vis spectra. Thin‐film X‐ray diffraction analysis and atomic force microscopy revealed high crystallinity on supporting substrates. In addition, as the substrate temperature has a significant influence on the morphology and the degree of crystallinity, the device performance could be optimized by varying the substrate temperature. These materials were found to exhibit optimal field‐effect performance, with a mobility of 0.17 cm² V^?1 s^?1 and an on/off ratio of 10⁵, at a substrate temperature of 70 °C.     

Multiple solutions for a nonlinear and non-homogeneous problem in Orlicz-Sobolev spaces

We study a non-homogeneous boundary value problem in a smooth bounded domain in R^N. We prove the existence of at least two non-negative and non-trivial weak solutions. Our approach relies on Orlicz-Sobolev spaces theory combined with adequate variational methods and a variant of Mountain Pass Lemma.     

A novel reagent for spectroscopic determination of Mo(VI)

A new reagent for spectrophotometric determination of Mo(VI) was developed utilizing micellar effects. For this purpose, differences in the ultraviolet and visible spectral properties of Mo(VI), gallic acid, L-serine, and their binary and ternary solutions were studied in the presence and absence of cationic, anionic, and non-ionic surface active agents. L-serine was observed to form binary complexes and a ternary complex with Mo(VI) and gallic acid below its isoelectric point. The maximum Mo(VI) sensitivity was exerted by the Mo(VI) + gallic acid + L-serine + hexadecyltrimethylammonium bromide system at pH of 4.5. This system was proposed for use in the spectrophotometric determination of Mo(VI) as a superior alternative to the Mo(VI) + gallic acid + hexadecyltrimethylammonium bromide system and to most of the instrumental analysis methods referred to in the literature. The mechanism of micellar effects was discussed on the basis of the spectral data obtained above and below the isoelectric point of L-serine and explained in terms of the molecular charge of the substrates and the surfactants.     

Spaces of idempotent measures of compact metric spaces

We investigate certain geometric properties of the spaces of idempotent measures. In particular, we prove that the space of idempotent measures on an infinite compact metric space is homeomorphic to the Hilbert cube.     

CaL-B a highly selective biocatalyst for the kinetic resolution of furylbenzthiazole-2-yl-ethanols and acetates

A highly stereoselective enzymatic kinetic resolution of novel various substituted racemic furylbenzthiazole-2-yl-ethanols and their acetates has been developed. Both processes, the enzymatic acylation of the racemic alcohols and the enzymatic methanolysis of racemic acetates yielded highly enantiomerically enriched (ee >98%) resolution product, when CaL-B was used as a biocatalyst in acetonitrile. The absolute configuration of the obtained (R)-(+)-1-(5-(4-chlorobenzo[d]thiazol-2-yl)furan-2-yl)ethanol was determined by a detailed ¹H NMR study of rac- and (+)-1-(5-(4-chlorobenzo[d]thiazol-2-yl)furan-2-yl)ethanol Mosher derivatives.     

Surface of Zn-Mn-O and its role in room temperature ferromagnetism: An XPS analysis

The existence of ferromagnetism in Zn-Mn-O semiconductor samples and dependence on the preparation condition were investigated. We systematically examined the samples with manganese concentration ranging from 0 to 10 at.%, prepared by a solid state reaction route using (ZnC₂O₄·2H₂O)_1−x and (MnC₂O₄·2H₂O)_x as precursors. Thermal treatment was carried out in air at temperatures ranging from 400 to 900 °C. The samples were investigated by X-ray diffraction, transmission electron microscopy, magnetization measurements and XPS spectroscopy. XPS surface composition, chemical analysis and depth profiling were successfully employed on powder revealing the chemical composition at the surface of the grains and underneath. The present investigation suggests that physical properties and observed room temperature ferromagnetism might be due to grain surface effects. It seems that the ferromagnetic phase is correlated with oxygen build up at the surface.     

Crystal Structure of Bis -(2,2′-bipyridine-N,N′)-(dicyanamide-N)-copper(II) Tricyanomethanide. Electronic and Structural Parameters Describing the Shape of Coordination Polyhedra in Five-Coordinated Copper(II) Compounds

 The structure of the new compound [Cu(bpy)₂N(CN)₂]C(CN)₃ (6) is compared with thestructures of six copper(II) coordination compounds with phenanthroline or bipyridine ligands and N-donor pseudohalide anions: [Cu(phen)₂NCS]C(CN)₃ (1), [Cu(bpy)₂NCS]C(CN)₃ (2), [Cu(phen)₂NCS]ONC(CN)₂ (3), [Cu(phen)₂N(CN)₂]C(CN)₃ (4), [Cu(bpy)₂C(CN)₃]C(CN)₃ (5), and [Cu(bpy)₂NCO]C(CN)₃ (7). The Cu(II) atoms in all above compounds are five-coordinated with an N-donor atom of the pseudohalide anion located in the equatorial plane of a deformed trigonal bipyramid. The shape of the coordination polyhedra and the degree of trigonal bipyramidal distortion towards a tetragonal pyramid are discussed and described using one electronic and several structural criteria which are discussed and compared.     

Monomer/polymer Schiff base copper(II) complexes for catalytic oxidative polymerization of 2,2′‐dihydroxybiphenyl

Catalytic oxidative polymerization of 2,2′‐dihydroxybiphenyl (DHBP) was performed by using both the Schiff base monomer‐Cu(II) complex and Schiff base polymer‐Cu(II) complex compounds as catalysts and hydrogen peroxide as oxidant, respectively. The dependence of monomer conversion and molecular weight distribution on various reaction parameters, including time, temperature, solvent as well as the amount of catalyst and oxidant were investigated. The structure of the poly‐2,2′‐dihydroxybiphenyl (PDHBP) was confirmed by UV‐vis, IR, ¹H and ¹³C NMR spectroscopy techniques. The electrochemical and thermal properties of PDHBP were also studied. DSC data revealed that PDHBP was amorphous. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2977–2984, 2009     

Preparation of a chromatographic solid support on the basis of perlite and separation of uranium on a TBP-loaded perlite column

The possibilities of preparing a packing for reversed phase column chromatography from Menderes' perlite were studied. Its physical and chemical characteristics were compared with other solid supports prepared from rocks, such as perlite and volcanic slags. A series of chemical treatments were applied to improve the mechanical and chemical properties of perlite. The experimental work covers the strong acid treatment, the strong base treatment and the silanization with DMCS. The raw perlite containing 70–73% SiO₂ was treated with NaOH to make soluble silicates and to increase it. Thus the surface and mechanical characters of the modified perlite were determined. The mean surface OH group density and the specific surface area were 3.2 μmol/m² and 9.2 m²/g, respectively. The modified perlite was silanized and hydrophized to load organic complexing agents. The TBP was fixed successfully on perlite up to 20% w/w. The packing prepared was used to study the chromatographic behavior of UO₂ ²⁺ Fe³⁺.