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  • Polymer and Materials Science  (29)
  • 1995-1999
  • 1990-1994  (29)
  • 1960-1964
  • 1945-1949
  • 1994  (29)
  • 1946
Collection
Publisher
Years
  • 1995-1999
  • 1990-1994  (29)
  • 1960-1964
  • 1945-1949
Year
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 2023-2037 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New fluorescent polymers for electroluminescent devices were synthesized and characterized. In order to obtain polymers for blue light emitting diodes (LEDs), two different structural concepts based on isolation of the active chromophore units within the polymer main chain were investigated. In the first approach non-coplanar units were used to reduce the conjugation length in poly(arylenevinylene)s. In a second approach copolymers having isolated chromophore units in the polymers main chain were investigated. For this purpose, copolyesters containing isolated 1,2-dinaphthylethene chromophore units were synthesized and characterized. The influence of the chemical structure on the photo- and electroluminescence is discussed. On the example of copolyester 2b, which shows bluegreen electroluminescence (λmax = 497 nm) in a LED configuration, it was demonstrated that these polyesters can be used as light emitting layer in electrooptical devices.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 25 (1994), S. 183-190 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: The metal forming process is one of the complicates mechanical deformation process. Up to this time, the investigations are mainly directed to the macroscopically point of view. Metal forming models are based on continuum mechanical methods.In opposite to the continuum mechanical deformation theory is the physics of metals.It is the aim of the paper, to discuss the developed technical supposition for using the micro-visioplasticity, an new method of micro-grid application and results of micro-grid deformation using an upsetting press.
    Notes: Der Umformprozeß gehört zu den kompliziertesten Verformungsvorgängen. Bis heute wurden die meisten Untersuchungen mit makroskopischen Theorien durchgeführt. Viele der Umformtheorien basieren auf der Kontinuumsmechanik. Demgegenüber sind mikroskopisch betrachtet jedoch auch metallphysikalische Prozesse interessant.In der Arbeit werden deshalb eine Einrichtung zur Durchführung von Versuchen - die Mikrovisioplastizität nutzend - die Grundlagen und Methoden zur Herstellung von Mikrorastern sowie erste Versuchsergebnisse vorgestellt.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 45 (1994), S. 21-28 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Microbial deterioration of materials - fundamentals: Mathematical modelling of destruction mechanismsModern trends in materials science require novel methods and strategies. The general aim is to describe by models the reactions occurring at the surface and within a solid. At the present time, however, it is only possible to derive, from the experimental work, mathematical relations, and this is not sufficient for a prediction of materials behaviour. On the basis of the three steps involved in the description of materials behaviour, i. e. rules of thumb, statistical evaluation of experimental data (including models developed for the presentation of reaction kinetics), and development of physical models (among others Monte Carlo simulations), these three steps and, in particular, the preliminary step of biocorrosion, i. e. biofilm formation, are discussed. Only physical models allow a prediction of reactions, although a prediction independent from experiment is not possible because of the unknown distributions of the acting energies and their possible fluctuations. Beyond that an outline is given of the description of corrosion reactions and crack propagation. A general problem, in particular in connection with biological reactions, is the lack of interdisciplinary education of scientists and engineers.
    Notes: Die moderne Entwicklung der Werkstoffwissenschaft bedingt einen Wandel in den Methoden und Strategien. Es wird angestrebt, die an und im Festkörper ablaufenden Reaktionen in Form von Modellen zu beschreiben. Gegenwärtig gelingt es aber nur, aus experimentellen Untersuchungen mathematische Zusammenhänge abzuleiten, womit eine Vorhersage des Werkstoffverhaltens mit theoretischen Mitteln nicht gelingt.Ausgehend von den drei Erkenntnisstufen zur Beschreibung des Werkstoffverhaltens, den Faustregeln, einer Auswertung von Experimenten mit statistischen Methoden, hierzu gehören auch reaktionskinetische Modellansätze, und der Entwicklung physikalischer Modelle, u.a. Monte-Carlo-Simulationen, werden diese insbesondere für die „Vorstufe“ der biokorrosiven Schädigung vorgestellt, der Biofilmbildng. Nur physikalische Modelle ermöglichen die „Voraussage“ von Reaktionsabläufen, wobei infolge der Unkenntnis der Verteilungen für die wirkenden Energien und deren möglichen Fluktuationen eine vom Experiment getrennte Voraussage nicht möglich ist.In einem Überblick wird darüber hinaus auch auf die Beschreibung von Korrosionsreaktionen und das Rißwachstum eingegangen. Ein generelles Problem, insbesondere im Zusammenhang mit biologischen Reaktionsabläufen, stellt die nicht fachgrenzenübergreifende Ausbildung von Naturwissenschaftlern and Ingenieuren dar.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 15 (1994), S. 303-310 
    ISSN: 1022-1336
    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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  • 5
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Remarkable shifts in chemical composition, molar mass, sequence length and sequence frequency will occur in the course of free-radical multicomponent polymerizations, if the reactivities of the comonomers are different and a simple batch reactor is used. It is shown for the terpolymerization system of methyl methacrylate/styrene/maleic anhydride that a semi-batch reactor with appropriate regimes is suitable to obtain products with improved chemical, molecular and sequential homogeneity. However, if polymers with defined inhomogeneities like bimodal molar mass or chemical composition distributions are desired, these are also obtainable by use of appropriate operational policies, which will be illustrated for the homopolymerization of methyl methacrylate and the binary copolymerization of methyl methacrylate/maleic anhydride. Concerning the instantaneous mean chemical composition of polymer molecules, which cannot be measured directly, a new procedure is presented to determine this quantity experimentally.
    Additional Material: 16 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 3579-3595 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of perfluoroalkyl-containing para-linked aromatic polyamides based on trifluoromethyl-p-phenylenediamine and a mixture of trifluoromethyl- and pentafluoroethyl-substituted terephthalic acid have been synthesized. The polyamides were prepared by a low temperature solution polycondensation of aromatic diacyl chlorides with N,N′-bis(trimethylsilyl)-substituted aromatic diamines. The influence of these perfluoroalkyl substituents on thermal properties, solubility and lyotropic behavior is discussed. 19F NMR spectroscopy was utilized for molecular weight determination and for further examination of the polymer structure.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 15 (1994), S. 279-284 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 855-883 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: With the help of a simple reaction-diffusion model with constant striation thickness the influence of micromixing on free-radical polymerization was investigated for several test reactions with discontinuous prepolymerization and jerky addition of selected reactants. Monomer conversion or mean values of molar mass and chemical composition cannot be expected to be very sensitive to micromixing effects. If molar mass distributions are to be used, problems will arise from the fact that the distribution of the polymer accumulated during prepolymerization covers mixing influences occurring after reactant feed. The instantaneous molar mass distribution would be more suitable. Time-integral distributions of chemical composition or sequence length in combination with appropriate test reactions proved to be feasible indicators for the effects of micromixing as it becomes possible to separate the distribution of the prepolymer from that of the polymer which is formed after addition when micromixing is to be investigated.
    Additional Material: 31 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 2191-2193 
    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
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 543-552 
    ISSN: 1040-0397
    Keywords: Chronopotentiometry ; Enzyme electrode ; Biosensors ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chronopotentiometry (CP) with enzyme electrodes is a new approach to overcome inherent problems of steady-state potentiometric processes. The developed procedure is presented on the example of a glucose oxidase (GOD) electrode. Electrochemically generated mediator helps to overcome traditional difficulties arising from poorly defined mixed potentials in the presence of oxygen during an analysis. Transition times are automatically evaluated by using computerized calculation programs. The technique can be used for determining substrate concentrations; moreover, it is particularly promising as an effective tool to study electrode processes with biochemical systems on an electrode surface.
    Additional Material: 11 Ill.
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