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  • Chemistry  (22)
  • Polymer and Materials Science  (17)
  • Aircraft Propulsion and Power
  • Condensed Matter: Electronic Properties, etc.
  • 1995-1999  (15)
  • 1975-1979  (7)
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1219-1227 
    ISSN: 0887-624X
    Keywords: 1,2,4-benzenetricarboxylic acid monoesters ; poly(amide-imide) structural regularity ; poly(amide-imide) “one-pot” synthesis ; 13C-NMR spectra of poly(amide-imide) ; phosphorylation reaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aromatic processable poly(amide-imide)s have been prepared according to the Yamazaki and Higashi phosphorylation reaction from flexible aromatic diamines and a mixture of isomeric 1,2,4-benzenetricarboxylic acid monoethylesters following a novel “one-pot” procedure. The polymerization was performed in 1-methyl-2-pyrrolidone/LiCl solutions using triphenylphosphite and pyridine as condensing agents to form amide bonds. Cyclization of the intermediate poly(amide-amic ethylester) occurred by eliminating ethanol under the polymerization conditions used, thus leading to the formation of imide rings. The influence of several parameters which regulate the degree of polymerization and the formation of the imide rings, such as reaction temperature, triphenylphosphite/monomers molar ratio, and pyridine concentration was carefully investigated. In particular, the catalytic activity of pyridine in the imidization reaction has been demonstrated. 13C-NMR spectroscopy has been used to show the absence of constitutional regularity in the prepared PAIs thus indicating equal reactivity toward polycondensation of the two different carboxyl groups of the 1,2,4-benzenetricarboxylic acid monoethylesters. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 2
    ISSN: 0899-0042
    Keywords: Circular dichroism ; helicity rule ; X-ray structure determination ; ultraviolet spectra ; n - π* and π - π* bands ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiroptical properties of a series of 3 and/or 4-heterosubstituted 2(5H)-furanones were investigated with respect to correlation with absolute configuration. The n - π* and π - π* Cotton effects have been assigned on the basis of comparison with the UV spectra in solvents of varying polarity. It is demonstrated that the n - π* transition in 4-amino substituted 2(5H)-furanones appears at shorter wavelength with respect to the π - π* transition. With the exception of 4-pyrrolidino and 4-benzylamino substituted 2(5H)-furanones, other heterosubstituted 2(5H)-furanones follow the butenolide configurational rule (Gawronski et al. J. Org. Chem. 61:1513-1515, 1996). Absolute configuration of 2(5H)-furanone derivatives can also be assigned according to the sign of the Cotton effect (of unknown origin) at 200-230 nm. The structure of four representative sulfur and nitrogen substituted 2(5H)-furanones has been analyzed by X-ray diffraction. The results indicate planarity of the furanone ring and extended conjugation in 4-amino substituted 2(5H)-furanones. Chirality 9:537-544, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 1477-1482 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 62 (1977), S. 85-90 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Reaktivität verschiedener monomerer Vinylketone bei der radikalischen Copolymerisation mit Methylmethacrylat und Vinylacetat wurden auf der Basis der Taft-Gleichung untersucht. Es ergab sich, daß die relative Reaktivität der Vinylketonmonomeren mit zunehmender Elektronegativität der Substituenten der verschiedenen Vinylketone steigt. Polare und sterische Effekte beeinflussen die Reaktivität nicht.
    Notes: The reactivity of some monomer vinyl ketones in the radical copolymerization with methyl methacrylate and vinyl acetate was studied on the basis of the Taft equation. It was concluded that the relative reactivities of the vinyl ketones in radical reactions increase with increasing electron-withdrawing nature of the vinyl ketone substituent. Polar and steric effects do not affect the reactivity.
    Additional Material: 1 Ill.
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  • 8
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic mechanical behaviour of polyamide systems containing different degrees of unsaturation was analyzed. The results do not show any simple relation between unsaturation and mechanical response. Particular attention was given to the α-transition, that is a glass transition, and experimental data suggest that the generally accepted mechanism for this transition requires a more extensive study.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to elucidate the relations between morphological habits, thermal behaviour and chemical structure of polymers, aliphatic polyesters with variable amount of trans-double bonds along the backbone chain were crystallized from dilute solutions in 1-propanol and 1-butanol. The crystals were studied with electron microscopy, differential scanning calorimetry, and wide angle X-ray diffraction. The morphology of solution grown single crystals and some thermodynamic quantities such as the equilibrium dissolution and melting temperature and the enthalpy and entropy of fusion are influenced by the percentage of unsaturated comonomer. The thermal behaviour and the X-ray diffraction of these crystals suggest that saturated and unsaturated repeating units are able to cocrystallize.
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 1037-1040 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the present paper we have investigated the role that the presence of trans double bonds plays on the glass transition temperature of linear polyesters. Experimental data indicate that the glass transition temperature is increased by an increase of the unsaturation concentration. The effect is not drastic but it is well detectable. This result is discussed taking into account the chain microstructure and the bulk structure effects.
    Additional Material: 1 Ill.
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