Atom transfer radical polymerization of cyclohexyl methacrylate at a low temperature

The atom transfer radical polymerization of cyclohexyl methacrylate (CHMA) is reported. Controlled polymerizations were performed with the CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalytic system with ethyl 2‐bromoisobutyrate as the initiator in bulk and different solvents (25 vol %) at 40 °C. The polymerization of CHMA in bulk resulted in a controlled polymerization, although the concentration of active species was relatively elevated. The addition of a solvent was necessary to reduce the polymerization rate, which was dependent on the dipole moment. Well‐controlled polymers were obtained in toluene, diphenyl ether, and benzonitrile solutions. Poly(cyclohexyl methacrylate) as a macroinitiator was used to synthesize the poly(cyclohexyl methacrylate)‐b‐poly(tert‐butyl methacrylate) block copolymer, which allowed a demonstration of its living character. In addition, two difunctional initiators, 1,4‐bis(bromoisobutyryloxy) benzene and 1,2‐bis(bromoisobutyryloxy) ethane, were used to initiate the atom transfer radical polymerization of CHMA. The experimental molecular weights of the obtained polymers were very close to the theoretical ones. These, along with the relative narrow molecular weight distributions, indicated that the polymerization was living and controlled. For confirmation, two different poly(tert‐butyl methacrylate)‐b‐poly(cyclohexyl methacrylate)‐b‐poly(tert‐butyl methacrylate) triblock copolymers were also synthesized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 71–77, 2005     

Der heutige Stand der Technik von Viskose-, Azetat- und Gelatinefilmen und ähnlichen Gebilden

Ohne Zusammenfassung     

Large time dynamics of a nonlinear spring–mass–damper model

In this paper we consider a nonlinear strongly damped wave equation as a model for a controlled spring–mass–damper system and give some results concerning its large time behaviour. It can be seen that the infinite dimensional system admits a two-dimensional attracting manifold where the equation is well represented by a classical nonlinear oscillations ODE, which can be exhibited explicitly. In contrast to other papers, this one applies Invariant Manifold Theory to a problem whose linear part is not self-adjoint.     

In search for mixed transition metal/lanthanide single-molecule magnets: Synthetic routes to NiII/TbIII and NiII/DyIII clusters featuring a 2-pyridyl oximate ligand

Employing the mononuclear complex [Ni{(py)C(Me)NO}₂{(py)C(Me)NOH}] (1) as ‘ligand’ [(py)C(Me)NOH = methyl 2-pyridyl ketone oxime], the use of the ‘metal complexes as ligands’ approach has led to the synthesis of the mixed Ni^II/Ln^III complexes [NiTb{(py)C(Me)NO}₂(NO₃)₃{(py)C(Me)NOH}] (2), [Ni₂Ln₂{(py)C(Me)NO}₆(NO₃)₄] (Ln = Dy, 3; Ln = Tb, 4) and [Ni₂Tb{(py)C(Me)NO}₆](NO₃) (5). The structures of 2, 3, and 5, and the magnetic properties of 2 and 5 are briefly discussed.     

New tetrafunctional monomer 1,3‐di(2‐hydroxy‐3‐methacryloyloxypropoxy)benzene in the synthesis of porous microspheres

Synthesis and properties of the new aromatic tetrafunctional methacrylate monomer 1,3‐di(2‐hydroxy‐3‐methacryloyloxypropoxy)benzene are presented. This monomer was applied for the synthesis of porous microspheres. It was copolymerized with trimethylolpropane trimethacrylate in the presence of pore‐forming diluents, decan‐1‐ol and chlorobenzene. Influence of diluents composition on their porous structures was studied. Thermal resistance and tendency to swell in different organic diluents for a chosen sample were also determined. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3190–3201, 2009     

Characterization of surface-active substances during a semi-field experiment on a phytoplankton bloom

The determination of surface-active substances (SAS) during the evolution of a phytoplankton bloom in a model plankton ecosystem was done by electrochemical methods. The separation and characterization of the organic material present were also done on XAD-8 resin columns. It was found that large amounts of the SAS, predominantly of the humic (fulvic) type, were present from the beginning of the experiment and partly masked the effects of organic substances released by phytoplankton. Although the transformation of the organic matter (consumption and/or excretion) was obvious, no general trend in the amount or type of surface-active matter was observed during the experiment.     

Experimental and kinetic modeling study of oxidation of acetonitrile

Oxidation of acetonitrile has been studied in a flow reactor in the absence and presence of nitric oxide. The experiments were conducted at atmospheric pressure in the temperature range 1150–1450 K, varying the excess air ratio from slightly fuel-lean to very lean. Oxidation of CH₃CN was slow below 1300 K. Nitric oxide, hydrogen cyanide and nitrous oxide were detected as important products. A detailed chemical kinetic model for oxidation of acetonitrile was developed, based on a critical evaluation of data from literature. The rate coefficients for the reactions of CH₃CN and CH₂CN with O₂ were calculated from ab initio theory. Modeling predictions were in satisfactory agreement with experiments. Calculations were sensitive to thermal dissociation of CH₃CN and to the branching fraction for CH₃CN + OH to CH₂CN + H₂O and HOCN + CH₃, respectively. More work is desirable for these steps, as well as for reactions of CH₂CN and HCCN.     

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl₂ ( 1 ), Ni(HL)Cl₂ ( 2 ), Cu(HL)Cl₂ ( 3 ), and Zn(HL)₃Cl₂ ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the Cu^II complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the Zn^II ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine Co^II, Ni^II, and Zn^II complexes in 10/90 (v/v) DMSO/water solution, whereas the Cu^II complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with Co^II, Ni^II and Zn^II, the 2:1 species with Co^II and Zn^II, and the 3:1 species with Zn^II. A distorted tetrahedral arrangement of the Cu^II complex was suggested on the basis of EPR and Vis/NIR spectra.     

Solvent extraction of Cu,Mo, V,and U from leach solutions of copper ore and flotation tailings

A micro-cloud point extraction method was discussed for preconcentration and spectrophotometric quantification of U(VI). The method depends on complex formation between U(VI) and 2-(4-sulphophenyloazo)-1,8-dihydroxy-3,6-naphtalenedisulphonic acid (SPADNS) at pH 7.0 and subsequent extraction of the complex in a mixed surfactant medium (cethyltrimethyl ammonium bromide and Triton X-114). The separation was carried out in the presence of 1% Na₂SO₄ at room temperature. The calibration curve was linear up to 3000 µg L^?1. The enrichment factor, detection limit and precision were 16.0, 1.05 µg L^?1, and 2.3%, respectively. The method was employed for the determination of U(VI) in real samples with different matrices.     

226Ra and uranium isotopic ratios characterization into the Gran Sasso aquifer,Italy

Journal of Radioanalytical and Nuclear Chemistry - Groundwater samples, collected into the deep underground facilities of Gran Sasso National Laboratory of the National Institute of Nuclear Physics...