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  • Polymer and Materials Science  (5)
  • Scanning electron microscopy  (1)
  • Wiley-Blackwell  (6)
  • Public Library of Science
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  • Wiley-Blackwell  (6)
  • Public Library of Science
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  • 1
    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: Methyl α-cyanoacrylate, when suitably inhibited by Lewis acids against anionic polymerization, can be polymerized readily with free-radical initiators to form hard, clear, high molecular weight polymers. The ratio of kp2/kt is approximately 0.021 at 60°C. if 100% efficiency of initiation by azobisisobutyronitrile is assumed. Acceleration occurs at very low conversion to polymer during bulk polymerizations. The homopolymer is thermally unstable at temperatures only slightly above the glass temperature (estimated to be 165-170°C.). Degradation of the polymer under gamma irradiation is pronounced, only 18 e.v. being required per main-chain scission.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 47 (1960), S. 75-89 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of methyl methacrylate and isopropyl acrylate in toluene with phenyl-H3-magnesium bromide has been studied at 0 and -70°C., respectively. Comparison of number-average molecular weights calculated from measurement of radioactivity and from measurements of appropriate colligative properties has shown that there is one and only one phenyl group per chain. Thus, initiation in this system is by 1,4-addition of the organomagnesium compound to the monomer. Methyl methacrylate, isopropyl acrylate, ethyl acrylate, and methyl acrylate were polymerized in toluene with phenylmagnesium bromide as the initiator. Isolation and identification of all the products have shown that, in addition to polymer, there are formed small amounts of two ketones and a hydrocarbon. Data are presented indicating that the principal mode of termination is via an intramolecular cyclization to give chains having a β-ketoester group on the end (arising from intramolecular reaction). A rationale for the stereospecificity, the termination reaction, and the large ratios of weight-average to number-average molecular weight in these polymerizations is proposed.
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymerizations of methyl methacrylate initiated by potassium and sodium amides in liquid ammonia solution proceed extremely rapidly even at low temperatures. The resulting polymers have relatively narrow molecular weight distributions M̄v/M̄n ∼ 1.5 and, unlike polymers of styrene prepared similarly, do not contain terminal amine groups. The molecular weight of poly(methyl methacrylate) prepared with potassium amide is independent of the monomer concentration and of the concentrations of potassium amide, potassium ion, and amide ion. The absence of terminal amine groups suggests that methoxide ion, produced by 1,2-addition of amide ion to the monomer, is the actual initiating species. The substantial absence of a termination step is indicated by the narrow distribution of molecular weights. Several minor variations of this general reaction sequence may give the experimentally observed independence of molecular weight on reactant concentrations. One such modification is considered by way of illustration, although final selection of a detailed mechanism is not possible on the basis of the present results.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
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  • 5
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isotactic (type II)polymers of methyl methacrylate are obtained from anionic polymerizations initiated by organolithium compounds at low temperature ( -70°)in toluene solution. The presence of small amounts of various ethers leads to polymers of reduced isotacticity; the effectiveness of these ethers in disrupting stereospecificity can be related semiquantitatively to their Lewis base strength. Certain Grignard reagents also produce highly isotactic polymer of methyl methacrylate, while others lead to less stereospecific results. The nature of the inorganic component of such initiators appears to determine the steric course of the addition reaction. The formation of a magnesium halide-monomer complex may be involved.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 5 (1987), S. 263-273 
    ISSN: 0741-0581
    Keywords: Immunocytochemistry ; Cell culture ; Cytoskeleton ; Scanning electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This technique permits the visualization of microtubules in situ by employing silver-enhanced immunogold labeling and backscattered electron imagery. For best results, monolayer cultures of PtK2 cells are lysed with Triton X-100 in a microtubule stabilizing buffer, fixed with 1% glutaraldehyde, reduced with NaBH4, incubated with monoclonal antitubulin and 5-nm gold-labeled anti-IgG, silver enhanced, freeze dried, lightly coated with aluminum, and examined in an SEM equipped with a backscattered electron detector. A high contrast view of the entire microtubule complex of each cell is obtained. Microtubules in freeze-dried preparations have relatively smooth surfaces, whereas those in critical point dried preparations are more irregular or beaded. At high magnifications, an unstained inner core of each microtubule can be resolved. Backscattered electron imaging appears to be a promising technique for localizing cytoskeletal proteins and other intracellular antigens that can be labeled with immunogold and enhanced with silver.
    Additional Material: 20 Ill.
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