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Elementary Analysis (elementary + analysis)

Distribution by Scientific Domains

Polymers and Materials Science	50%
Chemistry	33%

Selected Abstracts

Radical copolymerization of vinylidene fluoride with 1-bromo-2,2-difluoroethylene

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2010
G. K. Kostov
Abstract The radical copolymerization of vinylidene fluoride (VDF) and 1-bromo-2,2-difluoroethylene (BDFE) in 1,1,1,3,3-pentafluorobutane solution at different monomer molar ratios (ranging from 96/4 to 25/75 mol %) and initiated by tert -butylperoxypivalate (TBPPI, mainly) is presented. Poly(VDF- co -BDFE) copolymers of various aspects (from white powders to yellow viscous liquids) were produced depending on the copolymer compositions. The microstructures of the obtained copolymers were characterized by 19F and 1H NMR spectroscopy and by elementary analysis and these techniques enabled one to assess the contents of both comonomers in the produced copolymers. VDF was shown to be more incorporated in the copolymer than BDFE. From the extended Kelen and Tudos method, the kinetics of the radical copolymerization led to the determination of the reactivity ratios, ri, of both comonomers (rVDF = 1.20 ± 0.50 and rBDFE = 0.40 ± 0.15 at 75 °C) showing that VDF is more reactive than BDFE. Alfrey-Price's Q and e values of BDFE monomer were calculated to be 0.009 (from QVDF = 0.008) or 0.019 (from QVDF = 0.015) and +1.22 (vs. eVDF = 0.40) or +1.37 (vs. eVDF = 0.50), respectively, indicating that BDFE is an electron-accepting monomer. Statistic cooligomers were produced with molar masses ranging from 1,800 to 5,500 g/mol (assessed by GPC with polystyrene standards). A further evidence of the successful copolymerization was shown by the selective reduction of bromine atoms in poly(VDF- co -BDFE) cooligomers that led to analog PVDF. The thermal properties of the poly(VDF- co -BDFE) cooligomers were also determined and those containing a high VDF amount exhibited a high thermal stability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3964,3976, 2010. [source]

A cell boundary element method for elliptic problems,

NUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 3 2005
Youngmok Jeon
Abstract An elementary analysis on the cell boundary element (CBEM) was given by Jeon and Sheen. In this article we improve the previous results in various aspects. First of all, stability and convergence analysis on the rectangular grids are established. Moreover, error estimates are improved. Our improved analysis was possible by recasting of the CBEM in a Petrov-Galerkin setting. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005 [source]

Preparation and properties of dipropargyl ether of bisphenol A-modified bismaleimide resins and composites

POLYMER COMPOSITES, Issue 5 2008
Zhuxia Rong
A kind of modified bismaleimide resin, with good heat resistance and processing properties for advanced composites, was developed. The modifier, dipropargyl ether of bisphenol A (DPBPA), was prepared by a phase-transfer catalyzing procedure, characterized by FTIR, 1H NMR, and elementary analysis, and used to modify 4,4,-bismaleimidodiphenylmethane (BMDPM). The thermopolymerization of a DPBPA-modified BMDPM resin was followed up by FTIR. The curing of the resin was investigated by differential scanning calorimeter and gelation characterization. The relation of viscosity and temperature was used to characterize the processability of the resin. The results of DMA analysis showed that the cured DPBPA-modified BMDPM resins had a glass transition temperature higher than 320°C. The carbon fiber (T700) reinforced composites showed excellent flexural properties at ambient temperature and at 250°C. DPBPA could effectively improve mechanical properties without deteriorating heat resistance of the BMDPM resin a lot. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source]

Photoinitiated alternating copolymerization of vinyl ethers with chlorotrifluoroethylene

POLYMER INTERNATIONAL, Issue 7 2002
Manuel Gaboyard
Abstract The photoinitiated copolymerization of chlorotrifluoroethylene (CTFE) with several vinyl ethers [ethyl vinyl ether (EVE), 2-chloroethyl vinyl ether (CEVE), cyclohexyl vinyl ether (CHVE), 4-hydroxybutyl vinyl ether (HBVE)] was studied. CTFE is an acceptor monomer (e,,,1.5) whereas vinyl ethers are donor monomers (e,,,,1.5), and therefore their copolymerization led to alternating copolymers, as indicated by elementary analysis. The equilibrium constant (KF) of the charge-transfer complex formation (CTC) was determined by 19F NMR spectroscopy. Under our experimental conditions, KF was low for CHVE/CTFE and HBVE/CTFE systems, 0.058 and 0.013,l mol,1 respectively. It can be assumed that the copolymerization involves the free monomers rather than propagation via the donor,acceptor complex. The alternating structure arises from the great difference in polarity between the two types of monomers. Several functional copolymers were prepared in good yield and with molecular weight close to 15,000,g,mol,1. © 2002 Society of Chemical Industry [source]

Synthesis and Evaluation on Anticonvulsant and Antidepressant Activities of 5-Alkoxy-tetrazolo[1,5- a]quinazolines

ARCHIV DER PHARMAZIE, Issue 11 2009
Huo-Jian Wang
Abstract Several 5-alkoxy-tetrazolo[1,5- a]quinazoline derivatives have been synthesized by reacting 2,4-dichloroquinazoline with various phenols or aliphatic alcohol and then with sodium azide. The structures of these compounds have been confirmed by IR, MS, 1H-NMR, and elementary analysis. Anticonvulsant activities were evaluated using the maximal electroshock (MES) test. Most of the synthesized compounds displayed weak anticonvulsant activity at a dose of 300 mg/kg. Antidepressant activities were investigated by forced swimming test. Two compounds, namely 5-(hexyloxy)tetrazolo[1,5- a]quinazoline and 5-(4-methoxyphenoxy)tetrazolo[1,5- a]quinazoline, showed significant antidepressant activity, which decreased the immobility time by 62.2 and 51.7% at 100 mg/kg dose level. [source]

Synthesis of Novel Spiro Pyrrolidine and Pyrrolizine Derivatives by 1,3-Dipolar Cycloaddition

CHINESE JOURNAL OF CHEMISTRY, Issue 7 2010
Xiaofang Li
Abstract The 1,3-dipolar cycloaddition of azomethine ylides derived from isatin and amino acids viz. sarcosine and proline to 2-arylmethylidene-5,6-dihydroimidazo[2,1- b]thiazol-3(2H)-ones afforded novel spiro pyrrolidines and pyrrolizidines regio- and stereoselectively in moderate yields. The products were characterized thoroughly by IR, MS, NMR together with elementary analysis. [source]