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  • Articles  (22)
  • Chemistry  (22)
  • Polymer and Materials Science  (14)
  • Aircraft Propulsion and Power
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  • 1995-1999  (15)
  • 1985-1989  (7)
  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 3833-3844 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect and the role of halogenated molecules as additives for supported vanadium catalytic systems has been investigated both in high temperature ethylene homopolymerization and in its copolymerization with 1-hexene. Addition of CH3CCI3 to the {VCl3, xAICI3} or {VCl3, xCrCI3} system, leads to a strong productivity improvement. The intensity of the activating effect depends on the nature of the support. Results suggest that the activation involves both oxidation of V(II) deactivated species into potentially active trivalent ones, and generation of new active sites. Studies on the structure of ethylene/1-hexene copolymers show that the addition of halocarbons leads to copolymers with a higher comonomer content (SCB) and a better homogeneity in composition.
    Additional Material: 10 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 1691-1699 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The characteristic ratios of three samples of poly(1-hexadecene) with different tacticities were evaluated from intrinsic viscosity and molecular weight data obtained with a size exclusion chromatograph with dual (concentration plus viscosity) detector. No significant differences were found for the characteristic ratio in the studied range of tacticities. Theoretical calculations for the unperturbed dimensions were also performed for these samples by using the rotational isomeric state model, and compared with the experimental results.
    Additional Material: 4 Ill.
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  • 13
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Composition profiles generated by interdiffusion in the concentrated regime between poly(phenylene oxide)-polystyrene (PPO-PS) blend pairs are experimentally determined by two techniques. Three-point bending moment measurements over a convenient temperature range (DMA (dynamic mechanical analysis) method) are used to determine interphase composition profiles. Confocal micro-Raman spectroscopy is also used to measure local compositions along a direction which is perpendicular to the original interface. The study includes some limiting cases, to test accuracy, precision and flexibility of the “DMA method”. Excellent agreement is found between results obtained by both independent methods.
    Additional Material: 4 Ill.
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  • 14
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Multiring diamines and diacids containing ether and isopropylidene or hexafluoroisopropylidene bridges between phenyl groups were used alone or together with 1,4-phenylenediamine and terephthalic acid to prepare flexible or semirigid aromatic polyamides by direct polycondensation using triphenyl phosphite and pyridine as condensing agents. All the polyamides are readily soluble in N,N-dimethylacetamide, N-methyl-2-pyrrolidone and N,N-dimethylformamide. The wholly flexible polyamides are completely amorphous whereas those prepared from 1,4-phenylenediamine or terephthalic acid are partially crystalline and melt in the temperature range from 276 to 330°C. Thermal analysis shows Tg's in the range from 204 to 216°C for the wholly flexible polyamides and in the range from 239 to 257°C for the semirigid ones. Both classes of aromatic polyamides show excellent thermal resistance which is comparable with that of rigid-rod aramides.
    Additional Material: 2 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 233-246 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The crystallization kinetics of a polyetheretherketone (PEEK)/liquid crystalline polymer (LCP) blend was studied by using differential scanning calorimetry. Nonisothermal runnings were performed on heating and on cooling at different rates. Isothermal crystallization experiments at 315, 312, 310, and 307°C, from the melt state (380°C) were performed in order to calculate the Avrami parameters n and k and the fold surface free energy, σe. Polarized light optical micrographs were also obtained to confirm the Avrami predictions. It was observed that the LCP retarded the PEEK crystallization process and that the PEEK melting temperature decreased with the amount of LCP, but the LCP melting temperature increased with the amount of PEEK. Probably the PEEK improves the perfection of the LCP crystalline domains. A spherulitic morphology in pure PEEK and its blends was predicted by the Avrami analysis; however this morphology was only observed for pure PEEK and for the 80/20 composition. The other compositions presented a droplet and fibrillar-like morphology. The overall crystallization rate was observed to decrease with the crystallization temperature for all compositions. Finally, σe was found to decrease with the increase of LCP in the blends, having unrealistic negative values. Thus, calculations were made assuming σe constant at all compositions. It was observed that δ, the interfacial lateral free energy, decreased but still remained positive. It was concluded that in these blends neither σe nor σ could be considered constant. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 7 (1996), S. 385-392 
    ISSN: 1042-7147
    Keywords: polyamides ; poly(etheramide)s ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Processable, thermally stable aramides were prepared from multi-ring flexible aromatic diamines and diacids by direct polycondensation at 100°C with the triphenylphosphitel pyridine system in N-methyl-2-pyrrolidone/LiCl. The monomers used are characterized by the presence of all m-, all p-, or m, p-oriented aryloxy groups and, in some cases, by ring substitution with methyl or phenyl groups. The poly(etheramide)s (PEAs) prepared have moderate polymerization degrees (ηinh 0.55-2.74) and their solubility in organic solvents depends on their structural features. Differential scanning calorimetry (DSC), and wide-angle X-ray diffraction analysis revealed a partial crystallinity for “as-polymerized” PEAs derived from p-oriented monomers. The thermal behavior was investigated by DSC, dynamic-mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The glass transition temperatures, as determined by DSC and DMTA, are spread over a wide temperature range, 140-274°C, and depend on the number of aryloxy groups and their catenation as well as on the presence of ring substituents. The TGA results indicate thermal stability (10% weight loss) up to 490°C. Tough, flexible films are produced by solution casting or by compression molding in the case of amorphous PEAs.
    Additional Material: 2 Ill.
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  • 17
    ISSN: 1434-193X
    Keywords: Lithium ; Lithium trimethylsilyldiazomethane ; Heterocycles ; Uracil derivatives ; Pyrazolo[4,3-d]pyrimidindiones ; Pyrazolo[4,3-d]pyrimidindiones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nucleophilic addition of TMSC(Li)N2 at the low reactive C-5 position of the uracil ring of C-6 substituted uracil derivatives is reported. The ratio of C-5 versus C-6 nucleophilic addition of TMSC(Li)N2 dramatically depends on the stereoelectronic properties of the C-6 substituent. In particular, substituents characterized both by sterically bulky and/or electron-withdrawing (EWG) effects appear to direct the nucleophile mainly (methyl, chloromethyl or halogen) or completely (isopropyl) toward the C-5 position. The fine-tuned substituent selectivity found in the nucleophilic addition of TMSC(Li)N2 to C-6 substituted uracils plays a leading role in the synthesis of new trimethylsilyl-1H-[4,3-d]pyrimidin-5,7-dione derivatives, which can in turn be easily modified through known silicon chemistry.
    Additional Material: 1 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1988 (1988), S. 737-742 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese von Pyrimidin-Analoga des Nucleosid-Antibiotikums AscamycinVier Analoga des Ascamycins 〈5′-O′-O-[N-(L-alanyl)sulfamoyl]-2-chloradenosin〉(1), bei welchen der 2-Chloradenosinrest durch Uridin, Thymidin, Cytidin und 2′-Deoxy-5-methylcytidin ersetzt wurde, sind durch selektive Aminoacylierung der 5′-O-Sulfamoyl-Derivate 2, 9, 14 und 21 des 2′,3′-Di-O-acetyluridins, 3′-O-Acetylthymidins, 2′,3′-O-Isopropylidencytidins, bzw. des 3′-O-Acetyl-2′-deoxy-5-methylcytidins mit Boc-L-Ala-OSu in DMF und in Anwesenheit von DBU, mit nachfolgender Abspaltung der Schutzgruppen, erhalten worden. Ähnlich wurde 5′-O-[N-(D-Alanyl)sulfamoyl]uridin (8) ausgehend von Boc-D-Ala-OSu und 2 hergestellt. Die Verbindungen 14 und 21 wurden direkt durch Sulfamoylierung der 4-N-(Dimethylamino)methylen-Derivate 13 und 20 von 2′,3′-O-Isopropylidencytidin bzw. 3′-O-Acetyl-2′-deoxy-5-methylcytidin über die 5′-O-Tributylzinn-Zwischenverbindungen dargestellt. Verbindung 20 wurde aus 5′-O-Isopropylidencytidin bzw. 3′-O-Acetyl-2′-deoxy-5-methylcytidin über die 5′-O-Tributylzinn-Zwischenverbindungen dargestellt. Verbindung 20 wurde aus 5′-O-(tert-Bu-tyldimethylsilyl)thymidin (17) mittels Acetylierung und nachfolgende Überführung des Thymidinrestes in 5-Methylcytosin über das entsprechende Triazolylpyrimidinon unter Schutz der Amidingruppe erhalten.
    Notes: Four analogues of ascamycin 〈5′-O-[N-(L-alanyl)sulfamoyl]-2-chloroadenosine〉 (1) in which the 2-chloroadenosine moiety has been replaced by uridine, thymidine, cytidine, and 2′-deoxy-5-methylcytidine have been synthesized by selective aminoacylation of the 5′-O-sulfamoyl derivatives 2, 9, 14, and 21 of 2′,3′-di-O-acetyluridine, 3′-O-acetylthymidine, 2′,3′-O-isopropylidenecytidine, and 3′-O-acetyl-2′-deoxy-5-methylcytidine, respectively, with Boc-L-Ala-OSu in DMF and in the presence of DBU, followed by removal of the protecting groups. Similarly, 5′-O-[N-(D-alanyl)sulfamoyl]uridine (8) has been prepared from Boc-D-Ala-OSu and 2. Compounds 14 and 21 were directly prepared by sulfamoylation of the 4-N-(dimethylamino)methylene derivatives 13 and 20 of 2′,3′-O-isopropylidenecytidine and 3′-O-acetyl-2′-deoxy-5-methylcytidine, respectively, via the intermediate 5′-O-tributyltin derivatives. Compound 20 was obtained from 5′-O-(tert-butyldimethylsilyl)thymidine (17) by a route involving acetylation, conversion of the thymidine moiety into 5-methylcytosine through the corresponding triazolylpyrimidinone, and amidine protection.
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  • 19
    Electronic Resource
    Electronic Resource
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 9 (1988), S. 119-124 
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 20
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phonon spectra of thioanisole have been measured in a temperature range from the freezing point to 77 K, in order to ascertain if disordered crystalline phases are obtained as in other sulphur-containing molecular crystals studied. All the Davidov splitting components have been assigned on the basis of a correlation diagram which has been constructed assuming a unit cell isomorphous with a Cmc21 orthorhombic crystal.
    Additional Material: 4 Ill.
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