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111.
Cationic polymerization of styrene involving ionization of the C?Cl bond in ionic liquid/SO2 mixture
Małgorzata Baśko Tadeusz Biedroń Przemysław Kubisa 《Journal of polymer science. Part A, Polymer chemistry》2009,47(20):5251-5257
There has been a recent upsurge in interest in use of ionic liquids as reaction media for various chemical processes. Until recently, ionic liquids were considered as highly polar solvents. Our earlier investigation indicated that cationic polymerization of styrene initiated by aryl (alkyl) chlorides in ionic liquids may proceed even in the absence of coinitiator (Lewis acid). Polymerization, however, did not conform to controlled polymerization scheme. More recently, it has been claimed that ionic liquids are not as polar as it was previously assumed. Independently, high solubility of sulfur dioxide in ionic liquids was noticed. As sulfur dioxide displays a high ionizing power toward organic halides, we applied ionic liquid/sulfur dioxide mixture as a solvent in cationic polymerization of styrene initiated by aryl (alkyl) chlorides. Results show that in this reaction medium ionization of the C? Cl bond is facilitated, and the contribution of chain transfer reaction can be reduced as compared with polymerization in ionic liquid alone. Ionization of the C? Cl bond, however, is still not sufficiently fast to ensure conditions of controlled polymerization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5251–5257, 2009 相似文献
112.
Przemysław Rybiński Grażyna Janowska Agnieszka Kucharska-Jastrząbek Agnieszka Pająk Iwona Wójcik Dorota Wesołek Krzysztof Bujnowicz 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1219-1224
This article discusses the effect of the cross-linking of diene elastomers (BR, SBR, NBR), with the use of an organic peroxide
or sulfur, on their flammability and fire hazard. Flammability tests were carried out by the method of oxygen index, combustion
time (in air) and ignition temperature measurements. Fire hazard was determined on the basis of test results obtained by means
of a cone calorimeter. Toxicometric coefficients (
\textRTFH\textco/\textco 2 {\text{RTFH}}_{{{\text{co}}/{\text{co}}_{ 2} }} and WLC50SM) and the emission of polycyclic aromatic hydrocarbons (PAH) were determined. Test results were interpreted from the point
of view of the chemical constitution of elastomer macromolecules as well as the structure of its network structure. 相似文献
113.
The advanced two-plate model with BET adsorption equation has been verified by the use of the experimental Cu2+/Cu0 system in 1 M NaClO4/pH 3 solution at different scan rates and at 5, 10, 25 mM concentrations of Cu2+. A change of electrode properties during electrode process was included into the applied model. The model reflects a characteristic loop on cathodic part of CV response. The values of elementary kinetic parameters have been determined and discussed. 相似文献
114.
Ligand-free 5-endo-dig cyclization of 1,4- and 1,2,4-substituted but-3-yn-1-yl (homopropargyl) azides in the presence of zinc chloride (usually 20 mol %) in dichloroethane at elevated temperature provides 2,5-di- and 2,3,5-trisubstituted pyrroles in high to moderate yields (91-41%). Both conventional and microwave protocols furnished comparable results. A structure of 2-(4-fluorophenyl)-5-(4-methylphenyl)-1H-pyrrole was confirmed by X-ray crystallography. 相似文献
115.
Drzewicz P Afzal A Gamal El-Din M Martin JW 《The journal of physical chemistry. A》2010,114(45):12067-12074
The mechanism of hydroxyl radical initiated degradation of a typical oil sands process water (OSPW) alicyclic carboxylic acid was studied using cyclohexanoic acid (CHA) as a model compound. By use of vacuum ultraviolet irradiation (VUV, 172 nm) and ultraviolet irradiation in the presence of hydrogen peroxide UV(254 nm)/H(2)O(2), it was established that CHA undergoes degradation through a peroxyl radical. In both processes the decay of the peroxyl radical leads predominantly to the formation of 4-oxo-CHA, and minor amounts of hydroxy-CHA (detected only in UV/H(2)O(2)). In UV/H(2)O(2), additional 4-oxo-CHA may also have been formed by direct reaction of the oxyl radical with H(2)O(2). The oxyl radical can be formed during decay of the peroxyl-CHA radical or reaction of hydroxy-CHA with hydroxyl radical. Oxo- and hydroxy-CHA further degraded to various dihydroxy-CHAs. Scission of the cyclohexane ring was also observed, on the basis of the observation of acyclic byproducts including heptadioic acid and various short-chain carboxylic acids. Overall, the hydroxyl radical induced degradation of CHA proceeded through several steps, involving more than one hydroxyl radical reaction, thus efficiency of the UV/H(2)O(2) reaction will depend on the rate of generation of hydroxyl radical throughout the process. In real applications to OSPW, concentrations of H(2)O(2) will need to be carefully optimized and the environmental fate and effects of the various degradation products of naphthenic acids considered. 相似文献
116.
117.
Krzysztof Czolczynski Przemysław Perlikowski Andrzej Stefanski Tomasz Kapitaniak 《Communications in Nonlinear Science & Numerical Simulation》2012,17(9):3658-3672
We study the synchronization of a number of pendula mounted on a horizontal beam which can roll on the parallel surface. Under the driving moment, the pendula rotate in different directions: one of them rotates counterclockwise, the rest rotate clockwise. It has been shown that after a transient different types of phase synchronization between pendula can be observed, despite opposite directions of rotations. 相似文献
118.
Przemys?aw Rybiński Gra?yna Janowska Ma?gorzata Jó?wiak Agnieszka Paj?k 《Journal of Thermal Analysis and Calorimetry》2012,107(2):561-571
Heterobimetallic oxalato complex precursors, manganese(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (MnOLa), cobalt(II)pentaaquatris(oxalato)lanthanate(III)trihydrate
(CoOLa), nickel(II)pentaaquatris(oxalato)lanthanate(III)hexahydrate (NiOLa) and copper(II)diaaquatris(oxalato)lanthanate(III)monohydrate
(CuOLa) of the type, M3[La(C2O4)3(H2O)
m
]2·nH2O have been synthesized in aqueous medium. The precursors were characterized by elemental analysis, IR, electronic spectral
and powder X-ray diffraction studies. The good crystalline nature with monoclinic structures predominates in MnOLa and NiOLa
whereas triclinic structures were found in CoOLa and CuOLa. The solid-state thermal behaviour of the precursors was explored
using TG, DTG and DTA in air. The MnOLa generated a mixture species consisting mainly of MnO2, Mn3O4, Mn5O8, La2O3 and LaMn7O12 at 1000 °C through the formation of several intermediate species at 380 and 570 °C. The studies revealed that CoOLa led mainly
to LaCoO3 and La2CoO4 along with some oxides of both the cobalt and lanthanum at 1000 °C. In case of nickel analogue the mixture species identified
at 1000 °C are mainly of La2NiO4, La2O3, Ni2O3 and NiO2. In case of CuOLa the product at 1000 °C consisted of La2CuO4, La2Cu2O5 and oxides of copper and lanthanum. The nature of decomposition of the precursors in nitrogen were seen from DSC study and
the kinetic parameters i.e., E
*
, lnk
0, ΔH
#
, ΔS
#
and order of reaction of all the steps were evaluated and discussed. 相似文献
119.
Przemysław Rybiński Grażyna Janowska 《Journal of Thermal Analysis and Calorimetry》2014,117(1):377-386
The paper presents the results of investigating the effect of the density and spatial network structure of diene rubbers (NBR and SBR) on their thermal properties and fire hazard. The rubbers were either conventionally cross-linked by means of sulfur and organic peroxide or nonconventionally with the use of iodoform (CH3I). Based on thermo-kinetic analysis, the destruction activation energy of the elastomers investigated and their vulcanizates was determined under air and inert gas. The analysis of particular stages of their thermal decomposition was also presented. During the combustion of the elastomeric materials obtained, it has been found that their fire hazard depends not only on the elastomer chemical structure but also on the method of its cross-linking. 相似文献
120.
Piotr Garbacki Artur Teżyk Przemysław Zalewski Anna Jelińska Magdalena Paczkowska Alicja Talczyńska Irena Oszczapowicz Judyta Cielecka-Piontek 《Chromatographia》2014,77(21-22):1489-1495
A sensitive UHPLC-DAD method was developed for determination of diastereoisomers of cefuroxime axetil in bulk substance in amorphous and crystalline forms as well as in pharmaceutical preparations. Chromatographic separation was achieved on Kinetex C-18 (100 mm × 2.1 mm, 1.7 µm) column with mobile phase consisting of 0.1 % formic acid:methanol (88:12, v/v), at the flow rate of 0.7 mL min?1 and total run time of 3 min. The wavelength of the DAD detector was set at 278 nm. Inter-day precision (RSD) was less than 3 % and accuracy level ranged between 98.31 and 104.99 %. Degradation products of cefuroxime axetil in aqueous solutions and in the solid state were identified with a EIS-Q-MS mass spectrometer. The solubility of above-mentioned polymorphic forms of cefuroxime axetil in suitable solvents is a crucial factor during preparation of samples and is essential for chromatographic separation of its diastereoisomers. 相似文献