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  • Articles  (19)
  • Polymer and Materials Science  (19)
  • 1
    Electronic Resource
    Electronic Resource
    Reactions and kinetic modelling of silicone-carbon resins (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 248 (1997), S. 1-21 
    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: Die Berechnung der mittleren Molekulargewichte einer idealen, nichtlinearen, stufenweise ablaufenden Polymerisation von Comonomeren mit mehreen reaktiven Zentren im B-Zustand vor der Gelierung wird beschrieben. Ein kinetisches Modell wird angewendet, um den Verlauf der Polymerisation unter Berücksichtigung der Massenverhältnisse der möglichen, unterschiedlich substituierten Verbindungen zu simulieren. Die Molekulargewichte werden entweder durch Anwenden der Miller-Macosko-Methode oder durch Lösen der Diffentialgelicheungen für die Polymerisation von Verbindungen mit niedrigem Molekulargewicht erhalten. Die Näherung wird angewendet auf die mit Platin katalysierte Hydrosilylierung von methylsubstituiertem Cyclosiloxan mit Dicyclopentadien zu einem Hochleistungs-Silikon-Kohlenstoff-Harz. Die Näherung ergibt die Konzentrationen und Molekulargewichte der verschiedenen, zu jedem beliebigen Zeitpunkt der Reaktion vorhandenen Verbindungen. Unterschiedliche Arten der Monomeraddition können ebenfalls simuliert werden.
    Notes: This paper aims to calculate the average properties of ideal non-linear stepwise polymerization of comonomers containing multiple reacting sites at the B-stage prior to gelation. A kinetic model is used to simulate the polymerization process taking into account the mass balances of differently substituted species possible. The molecular weights are obtained either by the use of the Miller-Macosko method or by solving the differential equations for the polymerization of low-molecular-weight species. The approach is applied to the Pt-catalyzed hydrosilation reaction between methyl-substituted cyclosiloxane and dicyclopentadiene which produces a high-performance silicone-carbon. resin. The approach gives the concentrations of various species present at any given time and the molecular weights. Different modes of monomer addition can also be simulated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052480101
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  • 2
    Electronic Resource
    Electronic Resource
    13C Nuclear magnetic resonance characterization of poly(propylene) prepared with homogeneous catalysts (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 1931-1943 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The minor resonances in the 13C NMR spectrum of poly(propylene) prepared with soluble Group 4 metallocene/methylalumoxane catalysts are fully characterized. The 13C shifts for regioirregular sequences, chain-end structures, and 1,3-propylene adduct are obtained for both isotactic and atactic components. In both components the dominating mechanism is 1,2-insertion, with much lower amounts of 2,1-insertion and 1,3-insertion depending on the catalysts used. The isotactic component is stereoregular in all insertion modes. In the atactic components random stereosequences are observed. The regiostructures suggest that the propagation step is catalyticsite controlled even for the atactic component.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021900817
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  • 3
    Electronic Resource
    Electronic Resource
    Additive rules for the 13C NMR shifts of methyl-substituted alkanes and ethylene-propylene copolymersHercules Research Center Contribution Number 1854. (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 135-148 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Detailed 13C NMR chemical shift rules are devised for ethylene and propylene polymers and for low-molecular-weight analogs. The rules are additive and account for substituent effects as well as for configurational sequences. The agreement between the observed and the predicted shifts is excellent. A computer program has been written to obtain the predicted shifts quickly and with minimum effort.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021880112
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  • 4
    Electronic Resource
    Electronic Resource
    13C NMR characterization of copolymers of ethylene and perdeuteroethyleneHercules Research Center Contribution Number 1945. (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 845-849 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers of ethylene and ethylene-d4 were prepared, and their composition and comonomer sequence distribution determined from high-field 13C NMR spectra. For a conventional Ziegler-Natta catalyst, deuterium was shown to decrease the reactivity of ethylene.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890416
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  • 5
    Electronic Resource
    Electronic Resource
    Spectral simulation and characterization of polymers from ethene and propene by 13C NMRHercules Research Center Contribution Number 1819. (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 2665-2677 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A general treatment is devised for the 13C NMR spectral analysis of copolymers involving ethene and propene. The basis of the method is the computerized “synthetic approach” proposed earlier (Anal. Chem.) 56, 2320 (1984) and entails the use of first-order Markovian statistics, Monte Carlo polymer chain generation, spectral prediction, and spectral simulation. By this means, copolymer and homopolymer spectra of increasing complexity are readily simulated. The method is shown to accommodate all structural types (viz. stereosequences, regiosequences, and polymer chain ends) and provides good results for atactic poly(propylene), irregular poly(propylene), isotactic ethene/propene copolymers, ethene/propene rubbers, and ethene/propene oils.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021881117
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  • 6
    Electronic Resource
    Electronic Resource
    13C NMR characterization of ethylene oxide/epichlorohydrin copolymer (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 267-276 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 13C NMR spectra of ethylene oxide/epichlorohydrin copolymers are fully assigned. Information available includes copolymer composition, comonomer sequence distribution, and epichlorohydrin tacticity. The comonomer sequence distribution can be fitted to a two-component (Bernoullian/Bernoullian) statistical model.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920208
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  • 7
    Electronic Resource
    Electronic Resource
    13C-NMR characterization of poly(1,5-hexadiene)Hercules Research Center Contribution Number 1946. (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 35 (1988), S. 825-829 
    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: Poly(1,5-hexadiene) was prepared and its structure characterized by high-field 13C nuclear magnetic resonance. The polymer was shown to contain repeating five-membered rings separated by methylene bridges, with both cis and trans placements present in a 54 : 46 ratio. The result is compatible with the Marvel-Garrison two-step reaction mechanism.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070350321
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  • 8
    Electronic Resource
    Electronic Resource
    13C-NMR sequence determination for multicomponent polymer mixturesHercules Research Center Contribution Number 1953. (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 35 (1988), S. 1639-1650 
    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 general treatment is developed for the 13C-NMR analysis of polymers which contain several components. Reaction probability models and computer optimization techniques are used to resolve the NMR spectral data into separate components. The use of generalized multistate statistical models is introduced and is found to be very suitable for such systems. The computations are simplified by means of computer programs. The need for, and the relevance of, this approach are illustrated by the tacticity problems in polybutylene and polypropylene where two-state and three-state models are used, and copolymer triad sequence analysis for several olefin and acrylic copolymers where two-state models are needed. Three copolymer examples are given: propylene/butylene, ethylene/propylene, and acrylamide/acrylate.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070350619
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  • 9
    Electronic Resource
    Electronic Resource
    Stereochemistry of vinyl polymers and NMR characterizationHercules Research Center Contribution No. 1936. (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 229-241 
    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 configuration of vinyl polymers has been conventionally described by either Bovey's or Price's formalism. In this work, the relationships between these two formalisms are derived, and their relevance to polymerization mechanisms is delineated. Experimental data for nuclear magnetic resonance (NMR) pertaining to either chain-end control or catalytic-site control are tested using the computerized “analytical approach.” Suitable polymeric systems are illustrated.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360118
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  • 10
    Electronic Resource
    Electronic Resource
    Cis-Trans equilibrium and kinetic studies of acetyl-L-proline and glycyl-L-proline (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1465-1472 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By means of carbon-13 nmr (at 25 MHz) the trans/cis conformer ratio in glycyl-L-proline has been measured in aqueous (D2O) solution over the temperature range 33-96°C. It is found that ΔH0 = -4.2 kJ/mole and ΔS0 = -9.7 J/mole/K.Measurements of the T1 values for the proline ring carbons yielded values consistent with a fast puckering process involving both the β- and γ-carbons.Measurements of the rate of cis-trans conformational interconversion in glycyl-L-proline, using complete line-shape analysis for the glycyl α-carbon resonance, gave values for the trans → cis isomerization as follows: ΔH≠ = 83.5 ± 0.2 kJ/mole; ΔS≠ = 0.0 ± 10 J/mole/K. A more approximate determination from coalescence temperature observations gave a value of ΔG≠ of 82.0 ± 0.4 kJ/mole for this process in acetyl-L-proline in aqueous solution. The presence of 12M NaSCN lowered this barrier by ca. 2.6 kJ/mole.Such measurements are relevant to present theoretical models of the denaturation-renaturation processes in proteins, in which proline residues may play a key role.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160707
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