Copolymers dispersions designed to shaping of ceramic materials

Journal of Thermal Analysis and Calorimetry - To study the effect of ionic liquids (ILs) of the microstructure on the surface of the coal, four ILs ([Emim][BF4], [Bmim][BF4], [Bmim][NO3], and...     

Four copper(II) pyrazolido complexes derived from reactions of 3{5}-substituted pyrazoles with CuF(2) or Cu(OH)(2)

Treatment of CuF(2) with 2 equiv of 3{5}-[pyrid-2-yl]pyrazole (Hpz(Py)), 3{5}-phenylpyrazole (Hpz(Ph)) or 3{5}-[4-fluorophenyl]pyrazole (Hpz(PhF)) in MeOH, followed by evaporation to dryness and recrystallisation of the solid residues, allows solvated crystals of [{Cu(micro-pz(Py))(pz(Py))}(2)] (1), [{Cu(micro-pz(Ph))(2)}(4)] (2) and [Cu(4)F(2)(micro(4)-F)(micro-pz(PhF))(5)(Hpz(PhF))(4)] (3) to be isolated in moderate-to-good yields. Similar reactions of these three pyrazoles with Cu(OH)(2) in refluxing MeOH respectively afford 1, 2 and [Cu(pz(PhF))(2)(Hpz(PhF))(2)] (4) in ca. 10% yield. Crystalline 1 x 1/2H(2)O x 2CHCl(3) contains two independent dinuclear molecules with a puckered di-(1,2-pyrazolido) bridge motif, linked by a bridging, hydrogen-bonding water molecule. Compound 2 x 1/2C(5)H(12), containing cyclic, square tetranuclear complex molecules, is the first homoleptic divalent metal pyrazolide to have a discrete molecular rather than polymeric structure, for a metal other than Pd or Pt. The two independent complex molecules in 3 x 3/4CH(2)Cl(2) x Hpz(PhF) contain a unique tetrahedral [Cu(4)(micro(4)-F)](7+) core, three of whose edges are spanned by bridging pyrazolido groups. Magnetic data show that the copper centres in 1 and 3 are antiferromagnetically coupled, but that dried bulk samples of 2 do not retain their molecular structure.     

Issues dedicated to Alexander M. Ostrowski

Issues dedicated to Alexander M. Ostrowski     

(Co)polymerization behavior of supported metallocene catalysts. I. Ligand and substituent effect

Ethylene polymerization and its copolymerization with 1‐hexene with a set of supported metallocene catalysts were studied. As a carrier, the complex of magnesium chloride with tetrahydrofuran, which was previously pretreated with a triisobutylaluminium (TIBA), was used. The investigated metallocene compound differs in the metal type (Zr or Ti), the nature of the alkyl substituent in the cyclopentadienyl ring, and the type of ligand (Cp or Ind). The effect of catalyst composition on the anchored metal content, catalyst activity, comonomer reactivity, and polymer properties was investigated. The results obtained with supported catalysts were compared with those obtained with their homogeneous counterparts under the same (co)polymerization conditions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5562–5570, 2005     

Studies of structural composition distribution heterogeneity in ethylene/1-hexene copolymers using thermal fractionation technique (SSA): Effect of catalyst structure

Investigations into the compositional heterogeneity of ethylene/1-hexene copolymers obtained with various zirconocene/MAO catalysts, either homogeneous or supported on inorganic carriers such as a complex of magnesium chloride with tetrahydrofuran or methyl alcohol, were conducted. The dependence between metallocene structure, as well as catalyst immobilization, and the compositional heterogeneity of the related products was investigated. It was found that the heterogeneity of copolymers is determined by the metallocene catalyst structure. The amount of peaks on the DSC thermograms of copolymers and their division increase with the increase of bulkiness of the ligand in the catalytic system. The immobilization of the investigated catalysts on the magnesium carrier leads to an increase of the copolymer's compositional heterogeneity. However, the modification of the MgCl₂ carrier by tetrahydrofuran or methyl alcohol seems to not have any influence on the copolymers’ CCD.     

Laser flash photolysis of carboxymethylcellulose in an aqueous solution

Laser flash photolysis with excitation at 248 nm was used to study photochemically derived changes of carboxymethylcellulose (CMC) in aqueous solutions. Transient absorption spectra of solutions after photolysis revealed a broad band with a maximum of approximately 720 nm, which could be ascribed to the signal of the hydrated electron. The interaction of the hydrated electron with CMC was slow (<10⁷ dm³ mol^?1 s^?1), but the OH radical, formed by the decomposition of H₂O₂, reacted with CMC at a high rate constant (9.5–11.0 × 10⁸ dm³ mol^?1 s^?1). The rate constant of the reactions of CMC with hydroxyl radicals depended on the conformation of the macromolecules, which was determined by the pH of the solution. Transient absorption was recorded at a wavelength shorter than 370 nm for CMC solutions photolyzed in the presence of H₂O₂. As a result of OH attack, long‐lived radicals were formed on CMC. The recombination of macroradicals led to the formation of crosslinking bonds between side‐chain groups, and as a result of it an insoluble gel arose in low‐pH solutions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 505–518, 2005     

ODMR of bismuth and sulphur in GaP

Optically detected magnetic resonance (ODMR) of bismuth and sulphur impurities in GaP is reported. The results are compared to previous measurements by Cavenett et al. on GaP:N and further confirm the model proposed by these authors to explain the observed decrease in photoluminescence.     

Remarks on Naimark's duality

We present an extension of a version of Naimark's dilation theorem which states that complete systems in a Hilbert space are projections of -linearly independent systems of elements of an ambient Hilbert space. This result is presented in the context of other known extensions of Naimark's theorem.

     

Atomic characterization of the Hardy space of one-dimensional Schrödinger operators with nonnegative potentials

Given a Schrödinger operator on with nonnegative potential , we present an atomic characterization of the associated Hardy space .

     

Silver(I) chloride-polypyrrole composite: electrochemical preparation,characterization, and application as a SERS platform

Journal of Solid State Electrochemistry - A new electrochemical-chemical-electrochemical synthetic route to silver(I) chloride nanoparticle-polypyrrole composites is presented. The chemical...