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  • 1
    Electronic Resource
    Electronic Resource
    Torsional braid as a kinetic tool for the study of the polymerization of viscous materials. II. Catalytic effects in the polymerization of carboxylic acid-terminated polybutadiene prepolymers with tris[1-(2-methyl)aziridinyl]phosphine oxide (1968)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 12 (1968), S. 1959-1966 
    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 torsional braid technique for studying the polymerization of viscous substances has been extended to a study of the homogenous catalytic behavior of a number of acidic and basic catalysts int he polymerization of carboxy-terminated polybutadiene with tris(methyl aziridinyl)phosphine oxide. No general catalytic behavior was observed. Specific catalysis was observed in the case of lithium oleate, where the gel time was decreased, and in the case of bis(tri-n-butyltin) oxide, where the gel time was increased. The average energy of activation for all of these polymerizations was 13.9 ± 0.5 kcal./mole. This energy of activation and the reaction environment, when compared with the data in the literature, strongly suggest that the explanation that a change in the rate-determining step occurs as a function of the polarity of the reaction medium fails to account for all of the results.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1968.070120815
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  • 2
    Electronic Resource
    Electronic Resource
    Torsional braid as a kinetic tool for the study of the polymerization of viscous materials. I. Initial studiesProd. No. 1288 (1966)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 159-169 
    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 torsional braid experiment of Lewis and Gillham has been so modified that kinetic parameters can be obtained in polymerizations conducted with viscous prepolymers. The relative rigidity curve is interpreted in terms of extent of cure. The activation energy for the polymerization of a carboxyl-terminated polybutadiene with an aziridinyl compound has been measured.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1966.070100112
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  • 3
    Electronic Resource
    Electronic Resource
    Synthese und Struktur eines freien Germacyclopentadienid-Ions im Kristall: [Li([12]krone-4)2][C4Me4GeSi(SiMe3)3]Diese Arbeit wurde von der National Science Foundation gefördert. (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 107 (1995), S. 2029-2031 
    Details
    ISSN: 0044-8249
    Keywords: Aromatizität ; Germacyclopentadienid ; Heterocyclen ; Silacyclopentadienid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19951071724
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of a Free Germacyclopentadienide Ion: [Li([12]crown-4)2][C4Me4GeSi(SiMe3)3]This research was supported by the National Science Foundation. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 34 (1995), S. 1887-1890 
    Details
    ISSN: 0570-0833
    Keywords: aromaticity ; germacyclopentadienide ; heterocycles ; silacyclopentadienide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199518871
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  • 5
    Electronic Resource
    Electronic Resource
    Struktur-eigenschafts-zusammenhänge für poly(butadien-g-styren) - modell-polymereVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Kautschukelastische Polymersysteme” in Bad Nauheim vom 30. bis 31. März 1992 (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 202 (1992), S. 119-131 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to ascertain structure-property-relationships of poly(butadiene-g-styrene) copolymers the preparation of these model copolymers has been carried out by the anionic copolymerization of butadiene and styryl-terminated polystyrene macromonomers in solution. With this method it is possible to determine exactly the graft length and to vary the graft density or the polystyrene content. Besides, the products are almost free of homopolystyrene and are not cross-linked. The almost statistically regular distribution of the polystyrene grafts along the backbone chain has been achieved by the application of the initiator system: sodium tert-butoxide/n-butyl lithium.The materials have been tested by the determination of selected mechanical characteristic values. They yielded the following relationships: maxima of properties (stress strain, hardness, elasticity) already appear in the range of molar mass of the PS-grafts from 5 000 to 8 000 g/molethe position and the width of the maxima depend on the PB/PS-phase ratiowith increasing PS-content, the tensile strength increases up to about 20 MPa at nearly 40 %the hardness of the products is strongly and linearly influenced by the PS-contentthe elasticity shows a maximum in the range of 20 to 25 % PS-content.All in all, the materials exhibit good thermoelastoplastic behaviour in comparison with the SBS-three or -star block copolymers.Electron microscopic examination of the products result in phase separation phenomena.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.052020107
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  • 6
    Electronic Resource
    Electronic Resource
    Search for the sources of color in thermally aged, weathered and γ-ray irradiated bisphenol a polycarbonatePaper presented at the “16th International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 14-17, 1994. (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 232 (1995), S. 27-43 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Bisphenol A polycarbonate (BPA-PC) is an important high performance engineering thermoplastic well known for its outstanding combination of toughness, transparency and heat resistance. These properties make it an idel material for demanding applications where it is exposed to external stresses such as elevated temperatures, ultraviolet light and γ-ray sterilization. However, on extended exposure to these conditions, BPA-PC slowly degrades, turning progressively more yellow, eventually leading to a decrease in its physical properties. Over the years, there has been numerous studies made to understand these degradative processes so as to better design more stable BPA-PC formulations. In this paper, this chemistry is briefly reviewed along with more recent work in this area with a special emphasis on the efforts made to identifying the actual chemical species responsible for the observed yellow color and the chemistry responsible for their formation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052320103
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  • 7
    Electronic Resource
    Electronic Resource
    Helix-coil transition in nucleoprotein. Effect of ionic strength on thermal denaturation of polylysine-DNA complexes (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1681-1697 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal denaturation of direct-mixed and reconstituted polylysine-DNA complexes in 2.5 × 10-4 M EDTA, pH 8.0 and various concentrations of NaCl has been studied. For both complexes, increasing ionic strength of the solution raises Tm, the melting temperature of free base pairs. The linear dependence of Tm on log Na+ indicates that the concept of electrostatic shielding on phosphate lattice of an infinitely long pure DNA by Na+ can be applied to short free DNA segments in a nucleoprotein. For a direct-mixed polylysine-DNA complex, the melting temperature of bound base pairs Tm′ remains constant at various ionic strengths. On the other hand, the Tm′ in a reconstituted polylysine-DNA complex is shifted to lower temperature at higher ionic strength. This phenomenon occurs for reconstituted complex with long polylysine of one thousand residues or short polylysine of one hundred residues. It is shown that such a decrease of Tm′ is not due to a reduction of coupling melting between free and bound regions in a complex when the ionic strength is raised. It is also not due to intermolecular or intramolecular change from a reconstituted to a direct-mixed complex. It is suggested that this phenomenon is due to structural change on polylysine-bound regions by ionic strength. It is suggested further that Na+ may replace water molecules and bind polylysine-bound regions in a reconstituted complex. Such a dehydration effect destabilizes these regions and lowers Tm′. This explanation is supported by circular dichroism (CD) results.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130813
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  • 8
    Electronic Resource
    Electronic Resource
    Monte carlo simulations of peptide solvation (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 27-31 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To increase our understanding of peptide-water interactions, we are simulating the behavior of water molecules in the intermolecular channels of [Phe4Val6]antamanide dododecahydrate crystals. There is good overall agreement between the positions predicted using two alternative potential functions and those that have been observed by x-ray diffraction. Detailed differences between the predictions for the two potential functions are discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220106
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  • 9
    Electronic Resource
    Electronic Resource
    Protein hinge bending as seen in molecular dynamics simulations of native and M61 mutant T4 lysozymes (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 533-544 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dynamical model of interdomain “hinge bending” of T4 lysozyme in aqueous solution has been developed on the basis of molecular dynamics (MD) simulation. The MD model study provides a description of the conformational reorganization expected to occur for the protein in aqueous solution as compared to the crystalline environment. Three different 500 ps molecular dynamics simulations were calculated, each using a distinctly different crystal conformation of T4 lysozyme as the starting points of the MD simulations. Crystal structures of wild-type lysozyme and “open” and “closed” forms of M6I variant structures were analyzed in this study. Large-scale, molecular-conformational rearrangements were observed in all three simulations, and the largest structural change was found for the open form of the M6I allomorph. All three simulated proteins had closed relative to the wild-type crystal structure, and the closure of the “jaws” of the active site cleft occurred gradually over the time course of the trajectories. The time average MD structures, calculated over the final 50 ps of each trajectory, had all adapted to conformations more similar to each other than to their incipient crystal forms. Using a similar MD protocol on cytochrome P450BM-3 [M. D. Paulsen and R. L. Ornstein (1995) Proteins: Structure Function and Genetics, Vol. 27, pp. 237-243] we have found that the opposite type of motion relative to the starting crystal structure, that is, the open form of the crystal structure, had opened to a greater degree relative to the incipient crystal structure form. Therefore we do not believe that either result is merely a simulation artifact, but rather the protein dynamics are due to protein relaxation in the absence of crystal packing forces in the simulated solution environments. © 1997 John Wiley & Sons, Inc. Biopoly 41: 533-544, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Alternierende copolymerisation von butadien und ethen (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 196 (1992), S. 37-48 
    Details
    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: The copolymerization of butadiene and ethene in the presence of the catalyst dineopentyloxyvanadiumoxychloride/triisobutylaluminum was investigated. Basic reaction parameters, such as the [A1]/[V] ratio, the composition of monomer mixture and the polymerization temperature result in a significant influence on the progress of reaction, the conversion of monomers and on the molecular weight and polydispersity of copolymers obtained. NMR measurements demonstrate a high degree of alternation.A maximum of conversion and molecular weight was found by variation of the ratio of catalyst components at [A1]/[V] ≍ 7. An increase of ethene content in the monomer mixture also results in a maximum of conversion but, in contrast, in a continuous decrease in molecular weight. The increase of polymerization temperature from -25°C up to +40°C results in different effects on the yield of copolymers and appropriate data of molecular weight. The microstructure of products with a high content of trans-butadiene units exhibits an increase of 1,2-addition of butadiene and the beginning of crosslinking reactions at temperatures above 20°C.
    Notes: Es wurde die Copolymerissation von Butadien und Ethen in Gegenwart des katalysatorsystems Dineopetyloxyvanadiumoxychlorid/Aluminiumtriisobutyl untersucht. Die Variation der grundlegenden Reaktionsparameter [A1]/[V]-Verhältnis, Zusammensetzung der Monomermischug und Polymerisationstemperature ergab einen signifikanten Einfluß auf den Verlauf der Reaction, den Umsatz der Moomeren die, Molmasse und die Polydispersität der erhaltenen Copolymeren. NMR-Untersuchngen belegen einen hohen Alternierungsgrad.Bei der Variation des Verhaltnisses der Katalysatorkomponenten wurde ein Maximum für Umsatz und die Molmasse bei einem Verhältnis [A1]/[V] ≍ 7 ermittelt. Die Erhöhung des Ethengehaltes in der Moomermischung führt ebenfalls zu einer Erhöhung des Umsatzes. Dabei werden die Molmassen jedoch erniedrigt. Die Variation der Polymerisationstemparatur im Bereich von -25°C bis +40°C ergab für den Umsatz und die Molmasse Abhängigkeiten mit Minimum bzw. Maximum. Bei Polymerisationstemperaturen oberhalb +20°C ist ein Anwachsen der 1,2 -Addition des Butadiens und eine zunehmende Vernetzung der Produkte zu verzeichnen.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.051960103
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