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  • Polymers  (10)
  • Alkenes
  • Wiley-Blackwell  (16)
  • 1985-1989  (8)
  • 1960-1964  (8)
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  • Wiley-Blackwell  (16)
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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0570-0833
    Keywords: Oligomers ; Pleionomers ; Polymers ; Fibers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The term “oligomer” is defined, and a survey of methods for the isolation and synthesis of cyclic and linear oligoesters, oligourethanes, oligo(acrylonitriles), and oligoamides is presented. The oligomers serve a valuable function as model substances for the investigation of many properties of the corresponding high polymers. This is shown using several examples (infrared spectroscopy, X-ray spectroscopy, viscosity).
    Additional Material: 1 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0570-0833
    Keywords: Heat resistance ; Fibers ; Polymers ; Materials science ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This survey is principally concerned with papers published since 1959 on hydrocarbon polymers, aliphatic poly(terephthalamide) fibers, poly(hydroxybenzoic acid) films, poly(oxadiazole) fibers, poly(benzimidazole) films, poly(phenyltriazole) films, poly(pyromellitimide) films, and fibers from cyclized poly(acrylonitrile). All these materials have extremely high melting points and satisfactory in-use characteristics at high temperatures.
    Additional Material: 5 Ill.
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  • 13
    ISSN: 0570-0833
    Keywords: Surface recognition ; Molecular recognition ; Self-assembly ; Biological membranes ; Membranes ; Polymers ; Micelles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Part and the Whole. The principle of self-organization for the creation of functional units is not an invention of modern natural sciences. It was already a basic idea of the ancient philosophies in Asia and Europe: only the mutuality of the parts creates the whole and its ability to function. Translated into the language of chemistry this means: the self-organization of molecules leads to supramolecular systems and is responsible for their functions. Thermotropic and lyotropic liquid crystals are such functional units, formed by self-organization. As highly oriented systems, they exhibit new properties. The importance of lyotropic liquid crystals for the life sciences has been known for a long time. They are a prerequisite for the development of life and the ability of cells to function. In materials sciences this concept of function through organization led to the development of new liquid-crystalline materials. From the point of view of macromolecular chemistry, this review tries to combine these two different fields and especially hopes to stimulate their interaction and joint treatment. To exemplify this, the molecular architecture of polymeric organized systems will be discussed. Polymeric liquid crystals combine the ability to undergo spontaneous self-organization-typical of liquid-crystalline phases-with the polymer-specific property of stabilizing these ordered states. As new materials, polymeric liquid crystals have already been investigated intensively. As model systems for biomembranes as well as for the simulation of biomembrane processes, they so far have been little discussed. The intention of this review article is to show that polymer science is able to contribute to the simulation of cellular processes such as the stabilization of biomembranes, specific surface recognition, or even the “uncorking” of cells. Polymer science, having an old tradition as an inter-disciplinary field, can no longer restrict itself to common plastics. Attempts to reach new horizons have already begun. The borderland between liquid crystals and cells will certainly play an important role. Basic requirements to work in this frontier area between organic chemistry, membrane biology, life science, and materials science will be the delight in scientific adventures as well as the courage to go ahead. The most important prerequisite will be the willingness to cooperate with disciplines which so far have not really accepted each other. From this point of view, this review does not aim at giving defined answers. It wants instead to encourage the scientific venture: too often we cling to painfully acquired knowledge, fearing adventures.
    Additional Material: 78 Ill.
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  • 14
    ISSN: 0570-0833
    Keywords: Transition metals ; Polymers ; Alkene ligands ; Electrocatalysis ; Complexes ; Alkyne ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An unprecedented series of highly reactive alkene-and diene-complexes of the early transition metals (Groups 3A-5A of the periodic system) have been isolated recently. Diene complexes of this sort (M = Ti, Zr, Hf, Nb, Ta) prefer, besides the (η4-s-cis-diene)metal structure, either a novel bent η4-metallacyclo-3-pentene structure or the unique (η4-s-trans-diene)metal structure. In bis(diene)metal complexes of Nb and Ta the η4-s-cis-dienes assume an unusual exo-endo (supine-prone) geometry. The M—C bonds in these diene-metal complexes generally exhibit highly polarized σ-bonding along with π-bonding character. The complexes therefore undergo a variety of regio- and stereoselective carbometalations with substrates containing C—C, C—O, or C—N multiple bonds. Examples of the products that can be obtained include ketones, vinyl ketones, unsaturated primary, secondary, and tertiary alcohols, as well as diols and unsaturated acids. Mechanistic studies on the stoichiometric and catalytic conversions of unsaturated hydrocarbons provides, inter alia, some insights into the course of polymerization reactions.
    Additional Material: 7 Ill.
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  • 15
    ISSN: 0570-0833
    Keywords: NMR spectroscopy ; 13C NMR spectroscopy ; Polymers ; Analytical methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Until a few years ago, solid-state nuclear resonance yielded spectra containing broad lines only. Meanwhile, CP/MAS-NMR spectroscopy has provided a method which gives narrow nuclear resonance lines from a solid-state specimen as well. Using this technique, it is now possible to produce spectra of “rare” nuclei (13C, 29Si, 15N etc.) which are resolved in terms of chemical structure. The analytical capabilities of NMR spectroscopy can be applied to the solid state: it may be that it is necessary to identify compounds in the solid state because, for example, a solvent would alter the coordination sphere, or that it is desired to monitor chemical reactions in the solid state, for example the baking of an enamel. Where a substance in the solid state is concerned, high-resolution 13C-NMR spectroscopy provides not only information about the chemical structure, but also about the solid state itself. To mention just a few examples, information on the conformation, crystal structure and molecular dynamics, as well as molecular miscibility is given. This opens up a broad spectrum of applications, from a statement concerning the crystal modification of an active substance in ready-to-use pharmaceutical preparations, e.g. tablets, to the question of whether two polymers are miscible with one another at a molecular level.
    Additional Material: 17 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0570-0833
    Keywords: Stiff-chain polymers ; Polymers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most of the industrial plastics used up to now consist of flexible macromolecules in which the repeat units are joined together in a nonlinear fashion by rotating bonds. Stiff-chain polymers, which in the ideal case have a rodlike shape, have received much less attention. The reason for this is that such polymers usually exhibit an exceedingly low solubility. Very often, they are absolutely insoluble and do not melt. However, in recent years these polymers have aroused technical interest because high-modulus fibers and moldings can be fabricated from them. These favorable mechanical properties are directly related to the nearly parallel arrangement of the rodlike macromolecules in the solid state which is achieved through spinning or extrusion from a liquid crystalline (nematic) state. It is therefore evident that a thorough understanding of the phase behavior and the structure is required for a universal technical utilization of these materials. The great variety of methods used in polymer science today has led to a deeper understanding of stiff-chain polymers. Experimental results together with theoretical modeling of the phase behavior have direct implications for the practical use of these macromolecular materials.
    Additional Material: 19 Ill.
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