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  • Chemistry  (11)
  • CYBERNETICS  (2)
  • 42.60D
  • 1990-1994  (13)
  • 1950-1954
  • 1935-1939
  • 1994  (8)
  • 1992  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Crystallization study of a thermoplastic polyimide (new-TPI) (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 737-747 
    Details
    ISSN: 0887-6266
    Keywords: Crystallization ; melting ; morphology ; thermoplastic polyimide ; New-TPI ; PMDA ; 33BAPB ; polarizability ; SAXS ; lamellar thickness ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystallization, melting, and morphology of a thermoplastic polyimide (New-TPI) containing pyromellitic dianhydride (PMDA) and 3,3'-bis(4-aminophenoxy) biphenyl diamine (33BAPB) moieties have been studied. This material showed a glass transition temperature (Tg) of 250°C, an equilibrium melting temperature (T°m) of 406°C and a heat of fusion (ΔH) for 100% crystallinity of 6.38 kJ/mol. Measurements of the crystallization bulk rate (by DSC) and spherulite growth rate (by optical microscopy) indicated that the maximum crystallization temperature was about 320°C and the crystallization growth process was three-dimensional under thermal nucleation (the Avrami exponent n ca. 4). The rate of nucleation density was estimated to decrease with increasing temperature, and the product of two crystal surface free energies σeσo was calculated to be 1176 erg2/cm4. The meltgrown spherulite consistently showed a Maltese cross pattern with negative birefringence under cross-polars. The calculation of polarizability along the three unit cell axes suggested that the crystal b axis may be along the spherulite growth (radial) direction. Two scattering maxima were seen in small-angle x-ray scattering (SAXS) profiles. The dominant peak indicated a long period of ca. 20 nm which varied as a function of crystallization temperature. The weak peak at a d-spacing of 2.5 nm was independent of temperature and has been attributed to the chemical repeat distance determined by Okuyama et al. (indexed as 001). The lamellar thickness lc, estimated by the correlation function analysis of the SAXS data, was found to be similar to that determined by the Scherrer analysis of the 001 reflection peak. © 1994 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320415
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  • 2
    Electronic Resource
    Electronic Resource
    On the nature of order in wholly aromatic liquid crystalline random copolymers (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 1375-1385 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystalline aromatic copolymers, solid state order in ; copolymers, wholly aromatic, nature of order in solid state of ; solid state order in aromatic liquid crystalline random copolymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two different models of order in the solid state of wholly aromatic liquid crystalline copolymers (ALCPs), namely the nonperiodic layer (NPL) model of Windle et al. and the paracrystalline lattice (PCL) model of Biswas and Blackwell, have been analyzed with respect to experimental and theoretical observations. The NPL model proposes the formation of ordered domains by matching random sequences between adjacent chains while the PCL model relies on the presence of conformational correlations between adjacent monomers, without explicit sequence matching, to form ordered domains. The presence of three-dimensional order in the quenched state of ALCPs has been reported previously. The initial stages of crystallization are very likely to be assisted by the presence of small sequence matched domains. However, the probabilities for the formation of NPL domains having sizes comparable to those observed experimentally in the quenched state are extremely small. The PCL model, on the other hand, is not hampered by probability statistics and also provides a better fit to the experimental wide-angle x-ray scattering data along the fiber (Z) axis. The reported calorimetric data on ALCPs are also inconsistent with the presence of significant motion between chains, which is required for the NPL crystal to grow during the process of annealing. In contrast, the observation of a slow crystallization process, which converts the quenched hexagonal phase to the ordered orthorhombic phase, is adequately described by the PCL model as occurring via local conformational changes and small axial shifts between adjacent monomers. The observations from dielectric relaxation, nuclear magnetic resonance and dynamical mechanical spectroscopy studies also favor the PCL model over the NPL model of order in the solid state of ALCPs. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090301208
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and thermal stability, dielectric, and conductivity characteristics of some carbazole-bearing pendant and backbone sulfones (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1685-1692 
    Details
    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: A group of poly(N-vinylcarbazole) pendant polysulfones has been prepared by reacting it with benzene, toluene, p-chlorobenzene- and p-nitrobenzenesulfonyl chloride and N-methyl carbazole, 3,6-disulfonyl chloride by the Friedel Crafts reaction. Carbazole-based backbone polysulfones have also been prepared by the reaction of N-methyl carbazole, 3,6-disulfonyl chloride and biphenyl, naphthalene, anthracene, and carbazole in presence of anhydrous aluminum chloride. The various sulfone polymers, thus prepared, have been structurally characterized by elemental analysis and IR spectroscopy. Detailed analyses of thermal stability, dielectric, and conductivity characteristics have revealed certain significant differences between these two types of sulfone polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070451001
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal, stability, morphological, and conductivity characteristics of polypyrrole prepared in aqueous medium (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1575-1580 
    Details
    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 aqueous polymerization of pyrrole with varying FeCl3/Py mol ratio produces black insoluble powders. IR characterization reveals the shifting of the N—H stretching band to higher frequency with increasing FeCl3 amount in the feed composition due to lowering of intermolecular H-bonding. SEM shows a spongy texture of the polymer. TGA indicates the initial decomposition temperatures (180°-237°C) to be somewhat dependent on the FeCl3/Py feed ratio. DSC suggests the glass-transition temperature to be in the range 160-170°C for the polymers prepared with various feed compositions. The conductivity is also dependent on the FeCl3/Py feed composition and levels off at a value of ∼3 ohm-1cm-1. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510907
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  • 5
    Electronic Resource
    Electronic Resource
    Polymer blend: A novel method for the preparation of a natural rubber-carboxylated nitrile rubber blend (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1007-1014 
    Details
    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: Bis(diisopropyl)thiophosphoryl disfulfide (DIPDIS) can be successfully used to form a blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar NR through a chemical link between the two. It is revealed from the study that the physical properties of the vulcanizates obtained from the NR-XNBR blend could be significantly improved by the judicious selection of the NR:XNBR ratio. These properties can further be improved by two-stage vulcanization as described in the procedure. The SEM study reveals that it is possible to form a coherent blend of NR and XNBR in the presence of DIPDIS. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520801
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  • 6
    Electronic Resource
    Electronic Resource
    Chemical modification of of polypyrrole. I. Preparation and structural characterization of polypyrrole electrophically substituted with phthalic anhydride and pyromellitic dianhydride (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 843-847 
    Details
    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: Polypyrrole (PPY) prepared in ether and in aqueous medium has been modified by polycondensation with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA) in presence of Friedel-Crafts catalysts such as anhydrous zinc chloride and anhydrous ferric chloride at high temperature. The substitution reaction between PPY and the anhydrides presumably proceeds by intra-and interchain resulting in the formation of intractable products. The characterstic carbonyl absorption band expected for C—O and diketone groups in the proposed structure for the polycondensates has been observed in spectra of the anhydride-modified poly-condensates. XRD pattern of the polycondensates is totally amorphous. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540702
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  • 7
    Electronic Resource
    Electronic Resource
    Chemical modification of polypyrrole. II. Thermal stability, dielectric, and conductivity characteristics of polypyrrole substituted with phthalic and pyromellitic dianhydride (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 1483-1489 
    Details
    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: Polypyrrole (PPY) was electrophilically polycondensed with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA). PPY-PA and PPY-PMDA polycondensates were evaluated in regard to their thermal stability and dielectric and conductivity behavior. The overall thermal stability is in the order PPY 〈 PPY-PA 〈 PPY-PMDA, which may be rationalized in terms of intra- and intermolecularly cross-linked structures of the polycondensates. IR spectral analyses of PPY-PA and PPY-PMDA subjected to heating at 300, 400, 500, and 550°C, respectively, were conducted to understand some of the structural changes in the polymer matrices. Both PPY-PA and PPY-PMDA exhibit high dielectric constants (200 and 125) at low frequency (103 Hz), which fall monotonically with increasing frequency, suggesting the possibility of interfacial polarization. The conductivity values of PPY-PA and PPY-PMDA are in the range 10-3-10-4 ohm-1 cm-1, which are conspicuously lower than that for unmodified PPY (2.5). This is due to the adverse effect of incresing temperature on the PPY chain stability, whereby structural conjugation and eventually conductivity will be affected. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070541012
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  • 8
    Electronic Resource
    Electronic Resource
    SAXS investigations on chiral liquid crystalline polymers: antiferroelectric and ferrielectric structures? (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 257-262 
    Details
    ISSN: 1042-7147
    Keywords: Chiral liquid crystalline polymers ; Antiferroelectricity ; Ferrielectricity ; SAXS ; 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: The structure and phase behavior of liquid crystalline polymers (LCPs) having a common chiral side chain mesogen but different main chain structures have been investigated using small-angle X-ray scattering (SAXS). While the low molecular weight chiral side chain mesogen by itself exhibits ferroelectricity, the SAXS data of the side chain LCP with a flexible polyacrylate backbone contains a bilayered superstructure peak that is indicative of antiferroelectric order. The combined LCP with a nonpolar main chain mesogen also has a bilayered superstructure, but has a different structural organization in the proposed antiferroelectric phase compared to the side chain LCP. Further changes in the phase behavior and structural organization occur when a polar group is introduced into the main chain mesogen. A ferrielectric phase has been proposed to explain the observation of a trilayered superstructure in the corresponding SAXS data. The influence of the chemical structure and connectivity on the phase behavior and superstructure formation in the chiral LCPs is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030510
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  • 9
    Electronic Resource
    Electronic Resource
    Modification of styrene-divinylbenzene copolymer by anchoring ferric-dipyridylamine complex (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 1453-1460 
    Details
    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: Polystyrene-divinylbenzene (PS-DVB) copolymer was modified by anchoring dipyridylamine (DPA) on it followed by complexation with Fe(III). Under the experimental conditions followed, 9% incorporation of Fe(III) was achieved. PS-DVB-DPA and PS-DVB-DPA-Fe(III) were characterized by IR spectra. Diffuse reflectance spectra for PS-DVB-DPA-Fe(III) and DPA-Fe(III) revealed λmax at ∼ 360 and ∼ 310, respectively. This difference could be due to a difference in the nature of the coordinating moieties complexing with Fe(III) in these two systems. Scanning electron micrographs of PS-DVB, PS-DVB-DPA-Fe(III), and heat-treated PS-DVB-DPA-Fe(III) revealed some typical surface features. Thermal stability varied in the order PS-DVB-DPA-Fe(III) 〉 PS-DVB-DPA ≅PS-DVB, and DTA showed characteristic exotherms. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460816
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  • 10
    Electronic Resource
    Electronic Resource
    Some observations on morphology of anhydride-modified polystyrene (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 619-621 
    Details
    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: Friedel-Crafts acylation reaction between polystyrene and phthalic anhydride in the presence of AlCl3 has been performed in two different solvents, 1,2-dichloro ethane and nitro-benzene. The morphology of the condensate prepared in 1,2-dichloroethane has revealed the participation of 1,2-dichloroethane, i.e., a competitive Friedel-Crafts alkylation reaction.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440407
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