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  • Chemistry  (75)
  • Electronic structure and strongly correlated systems
  • 1995-1999  (75)
  • 1995  (75)
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1433-1439 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 fracture toughness of acrylonitrile-butadiene-styrene (ABS) was determined by three J-integral methods, ASTM E813-81, E813-87, and by hysteresis. The critical J values (J1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813-81 and hysteresis methods result in comparable J1c values, whereas the ASTM E813-87 was ∼40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the corresponding J1c represents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to the J1c obtained from the E813-81 or the hysteresis method.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 190-194 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolytheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1015-1028 
    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: This article reveals that the already known improved properties of the thermoplastic-liquid crystalline polymer (LCP) blends can be further improved substantially over the corresponding noncompatibilized counterparts by using a reactive in situ type compatibilizer, the styrene-glycidyl methacrylate (SG) copolymer. This SG copolymer has been demonstrated in this article to be an effective reactive compatibilizer to improve the processability, heat deflection temperature, and mechanical properties of Noryl/LCP blends. The epoxy functional groups of the SG copolymer can react with the end groups of PPO (in Noryl) and LCP. The in situ-formed SG-g-LCP copolymer tends to reside along the interface of Noryl-LCP and reduces the interfacial tension during melt processing. The resultant LCP fibers in the Noryl matrix of the compatibilized blends have a higher aspect ratio because the fibers become finer, longer, and tend to form lamellate domains with a greater interphase contact area than those from the noncompatibilized blends. The compatibilized blends also improve the interphase adhesion between Noryl and LCP. The presence of ethyl triphenylphosphonium bromide catalyst promotes the grafting reaction to improve blend compatibilization. © 1995 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 133-144 
    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 wasserlöslichen aromatischen Diazonium-Doppelsalze p-Diazodiphenylaminchlorid/Zinkchlorid (DZS-1) und p-Diazoanisolchlorid/Zinkchlorid (DZS-2) wurden auf ihre Verwendbarkeit als photobleichbare Farbstoffe in der Kontrastverstärkungslithographie untersucht. Nach Untersuchung der Bleicheigenschaften der hergestellten Salze wurde DZS-1 in wäßrigen Lösungen mit Poly(vinylalkohol) als Kontrastverstärkungssystem eingesetzt. Die thermische Stabilität, der Resistkontrast, die Bestrahlungsparameter und andere Bleicheigenschaften wurden untersucht. Im Vergleich zu einem handelsüblichen i-Linien-Photoresist beträgt das Kontrastverhältnis der DZS-1/PVA CEL-Schicht 1,67.
    Notes: Water soluble aromatic diazonium double salts, p-diazodiphenylamine chloride zinc chloride (DZS-1) and p-diazoanisol chloride zinc chloride (DZS-2), have been evaluated as photobleachable dyes for contrast enhancement lithography. After testing the bleaching characteristics, aqueous solutions of DZS-1 and poly(vinyl alcohol) were used as a contrast enhancement material. Thermal stability, resist contrast, exposure parameters and other bleaching characteristics of the photobleachable membranes were investigated. A. commercial i-line photoresist was used to evaluate the contrast ratio of the DZS-1/PVA CEL layer. The contrast ratio obtained in this investigation is 1.67.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 230 (1995), S. 47-71 
    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 Glykolyse von Poly(ethylenterephthalat) mit Bisphenol A wurde bei hohen Temperaturen zwischen 190°C und 230°C in einem Autoklaven durchgeführt und die Kinetik der Depolymerisation wurde untersucht. Die Reaktionstemperatur und das Verhältnis von Poly(ethylenterephthalat) und Bisphenol A erwiesen sich als bestimmend für die Reaktionsgeschwindigkeit und den Glykolysegrad. Zur exakten Beschreibung der Kinetik wurde ein aus sechs Gleichgewichtsreaktionen bestehender Reaktionsmechanismus vorgeschlagen, mit dem durch numerische Integration nach Runge-Kutta die kinetischen Parameter berechnet wurden. Die sehr gute Übereinstimmung zwischen den berechneten und den experimentellen Werten bestätigte die Richtigkeit des Mechanismus.
    Notes: Glycolysis of poly(ethylene terephthalate) with bisphenol A at high temperature (190°C-230°C) was carried out in an autoclave reactor. Kinetic study on depolymerization of glycolysis was conducted. The reaction temperature and the ratio of bisphenol A to poly(ethylene terephthalate) played the key roles on the reaction rate and the extent of glycolysis. For describing the kinetic behavior properly, a mechanism consisting of six principle equilibrium reactions was proposed. Based on this mechanism, the kinetic parameters were obtained through the Runge-Kutta numerical integration. Excellent agreements between the calculated values and the experimental data were achieved, thus verified the appropriateness of the proposed mechanism.
    Additional Material: 20 Ill.
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  • 6
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano (4), one ethano and one propano (5), and two propano bridges (6) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane (7) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4-6.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2119-2125 
    ISSN: 0887-624X
    Keywords: thermotropic ; liquid crystalline poly(amide-ester) elastomer ; direct polycondensation ; two-phase morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three series of novel poly(amide-ester) (PAE) elastomers were prepared by direct poly-condensation from terephthalic acid (TPA), polyols (Mn = 1000 or 2000), and various diamines. The structures and thermal properties of the synthesized PAEs were examined by FTIR spectroscopy, wide angle X-ray diffraction (WAXD), differential scanning calo-rimetry (DSC), thermal optical polarized microscopy, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The effects of kinds and amount of diamines and the molecular weight of polyols on the thermal properties of PAEs were studied. By introducing long flexible spacers (PE-1000 or PE-2000) into the polymer main chain, all polymers showed two-phase morphology under the thermal optical microscopic observation. It was interesting that most of the synthesized polymers exhibited only one melting transition corresponding to the soft segments. The melting transition of hard segments could not be detected due to decomposition of the soft segments. However, a thermotropic liquid crystalline PAE (TLCPAE) prepared from methylhydroquinone and 2-chloro-5-methyl-phenylenediamine with PE-1000 could be obtained by lowering the melting transition temperature of the hard segment. © 1995 John Wiley & Sons, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2127-2133 
    ISSN: 0887-624X
    Keywords: liquid crystalline polyester elastomer ; direct polycondensation ; two-phase morphology ; smectic phase ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three series of novel thermotropic liquid crystalline polyester elastomers (TLCPEEs) were prepared by direct polycondensation from terephthalic acid, polyols (Mn = 1000 or 2000), and various diols. The structures and thermal properties of the synthesized TLCPEEs were examined by FTIR spectroscopy, differential scanning calorimetry, thermal optical polarized microscopy, thermogravimetric analysis, and wide-angle x-ray diffraction. The effects of kinds and amount of diols and the molecular weight of polyols on the thermal properties of TLCPEEs were studied. By introducing long flexible spacers (PE-1000 or PE-2000) into the polymer main chain, all polymers showed two-phase morphology under the thermal optical microscopic observation. All of the synthesized polymers, except polymer P1-BPA60 and P2-BPA60, which were prepared from BPA, exhibited thermotropic liquid crystalline properties that were in the smectic phase. © 1995 John Wiley & Sons, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1075-1083 
    ISSN: 0887-624X
    Keywords: crosslinkable ; liquid crystalline poly(ether ester) ; vinyl monomer ; photoirradiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of crosslinkable thermotropic liquid crystalline poly(ether-ester)s and copoly(ether-ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo-irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc.
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  • 10
    ISSN: 0887-624X
    Keywords: polynucleotide analogues ; alternating copolymers ; hypochromicity ; hyper-chromicity ; excimer fluorescence ; polyelectrolyte effects ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Amino-6-chloropurine was reacted with 2-(tosyloxymethyl)-2,3-dihydro-2H-pyran to give 2-(2-amino-6-chloropurin-9-ylmethyl)-2,3-dihydro-2H-pyran (3) and its N7-isomer (4), which were treated with 5% aqueous trimethylamine to result in 2-(guanin-9-ylmethyl)-2,3-dihydro-2H-pyran (5) and its N7-isomer (6), respectively. 2-(N2-Acetylguanin-9-yl-methyl)-3,4-dihydro-2H-pyran (7) and 2-(N2-acetylguanin-7-ylmethyl)-3,4-dihydro-2H-pyran (8), obtained by acetylation of compounds 5 and 6, were copolymerized with maleic anhydride to give the alternating copolymers 9 and 10, and they were hydrolyzed to result in poly[ {2-(guanin-9-ylmethyl)tetrahydropyran-5,6-diyl} {1,2-dicarboxyethylene}] (11) and poly[ {2-(guanin-7-ylmethyl)tetrahydropyran-5,6-diyl} {1,2-dicarboxyethylene}] (12), re-spectively. Polymer 11 showed hypochromicity whereas 12 exhibited hyperchromicity in aqueous solutions. Polymers 11 and 12 in aqueous solutions showed very strong excimer fluorescence with the maximum intensities at 432 and 446 nm, respectively, at room tem-perature. The two polymers showed polyelectrolyte effects, e.g., very high GPC molecular weights as well as reduced viscosities at low concentrations in water. Normal behavior was retained by addition of inorganic salts. Sodium salts of polymers 11 and 12 migrated to the anode by electrophoresis and both showed two bands. © 1995 John Wiley & Sons, Inc.
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