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  • 1
    Electronic Resource
    Electronic Resource
    Cyclopropanation of poly[(methylphenylsilanediyl)-(Z)-butenylene]. Synthesis and characterization of poly[(methylphenylsilanediyl)methylenecyclopropylenemethylene] (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 2173-2180 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly[(methylphenylsilanediyl)methylenecyclopropylenemethylene] (3a) was prepared by cyclopropanation of the C—C double bonds of poly[(methylphenylsilanediyl)-(Z)-butenylene] (2a) by a Simmons-Smith reaction. Alternatively, 3a was prepared by a Birch reduction of the dichlorocarbene adduct poly[(methylphenylsilanediyl)methylene(2,2-dichloro-1,3-cyclopropanediyl)-methylene] (4a). Both 3a and 4a show the characteristic absorptions in the 1H, 13C, and 29Si NMR, IR and UV spectra. Their molecular weight distributions, determined by GPC, are rather broad and their thermal stabilities (by TG) are relatively high.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910918
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  • 2
    Electronic Resource
    Electronic Resource
    Phenyl-2,4,6-trimethylbenzoylphosphinates as water-soluble photoinitiators. Generation and reactivity of O=Ṗ(C6H5)(O-) radical anions (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 2307-2315 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Lithium- and magnesium phenyl-2,4,6-trimethylbenzoylphosphinates (TMPPL and TMPPM) are effective water-soluble photoinitiators for the free-radical polymerization of appropriate monomers such as acrylamide (AA) and methacrylamide (MAA) in aqueous solution. They are also capable of initiating the polymerization of other olefinic compounds such as styrene (St), methyl methacrylate (MMA) or acrylonitrile (AN) in water-containing solvent mixtures such as 1:1 water-acetonitrile mixtures. This is due to the fact that TMPPL and TMPPM undergo α-scission with a rather high quantum yield (φ(α) ≈ 0,35) resulting in the formation of 2,4,6-trimethylbenzoyl radicals and O=Ṗ (C6H5)(O-) radical anions. The latter are very reactive toward olefinic monomers. Bimolecular rate constants kR+M/(L/(mol · s)) were determined by flash photolysis at room temperature, e. g. in neat water: 3,8 · 108 (MAA), 2,2 · 108 (AA), and in H2O/CH3CN (1:1, v/v): 1,8 · 107 (St), 1,2 · 108 (MMA), 8,4 · 107 (AN).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021921010
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  • 3
    Electronic Resource
    Electronic Resource
    Studies of the metathesis polymerization and copolymerization of syn- and anti-7-methylnorbornene initiated by the tungsten-carbene complex (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 2237-2251 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The tungsten-carbene complex was used to initiate the metathesis polymerization of syn-and anti-7-methylbicyclo [2.2.1] hept-2-ene (Ms and Ma). Two kinds of experiment were performed:(i) the reactions were followed at low monomer/initiator ratios by 1H NMR spectroscopy at 220-250K; (ii) polymers and copolymers of Ms and Ma were prepared at room temperature and their microstructure analysed by 13C NMR spectroscopy. The propagating tungsten-carbene species derived from both Ma could be detected. Some rate constants were evaluated for various steps in the mechanism. A polymer of Ms was prepared for the first time, containing 90% trans double bonds and probably isotactic. After hydrogenation this polymer exhibits two first-order transitions, with DSC maxima at 179 and 230°C. Hydrogenated atactic polymers of Ma and of norbornene also exhibit first-order transitions. Conditions are described for the preparation of block and tapered block copolymers of Ma and Ms.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021911003
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  • 4
    Electronic Resource
    Electronic Resource
    Addition of chlorofluorocarbene to poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) and poly(1,1-dimethyl-1-sila-cis-pent-3-ene): Characterization of chlorofluorocyclopropanated polymer microstructures by 1H-, 13C-, 19F-, and 29Si-NMR spectroscopy (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1789-1798 
    Details
    ISSN: 0887-624X
    Keywords: chlorofluorocyclopropanated polymers ; carbosilane polymers ; thermal stability ; synthesis ; characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chlorofluorocarbene, generated by the sodium iodide catalyzed decomposition of phenyl(dichlorofluoromethyl)mercury, adds to the carbon-carbon double bonds of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (I) and poly(1,1-dimethyl-1-sila-cis-pent-3-ene) (II) to yield poly(3,4-chlorofluoromethylene-1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (CIFC-I) and poly(3,4-chlorofluoromethylene-1,1-dimethyl-1-sila-cis-pent-3-ene) (CIFC-II). Similarly, two series of random partially chlorofluorocyclopropanated polymers have been prepared. The microstructures of these adduct polymers have been determined by 1H-, 13C-, 19F-, and 29Si-NMR spectroscopy. The glass transition temperatures (Tg's) depend on the extent of chlorofluoropropanation of these polymers. These copolymers become less thermally stable as the extent of chlorofluorocyclopropanation increases. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310718
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  • 5
    Electronic Resource
    Electronic Resource
    On the dependence of molecular conformation on the type of solvent environment: A molecular dynamics study of cyclosporin A (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1669-1687 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dependence of the conformation of cyclosporin A (CPA), a cyclic undecapeptide with potent immunosuppressive activity, on the type of solvent environment is examined using the computer simulation method of molecular dynamics (MD). Conformational and dynamic properties of CPA in aqueous solution are obtained from MD simulations of a CPA molecule dissolved in a box with water molecules. Corresponding properties of CPA in apolar solution are obtained from MD simulation of CPA in a box with carbontetrachloride. The Results of these simulations in H2O and in CCl4 are compared to each other and to those of previous simulations of crystalline CPA and of an isolated CPA molecule.The conformation of the backbone of the cyclic polypeptide is basically independent of the type of solvent. In aqueous solution the β-pleated sheet is slightly weaker and the γ-turn is a bit less pronounced than in apolar solution. Side chains may adopt different conformations in different solvents. In apolar solution the hydrophobic side chain of the MeBmt residue is in an extended conformation with its hydroxyl group hydrogen bonded to the backbone carbonyl group. In aqueous solution this hydrophobic side chain folds over the core of the molecule and the mentioned hydrogen bond is broken in favor of hydrogen bonding to water molecules. The conformation obtained from the MD simulation in CCl4 nicely agrees with experimental atom-atom distance data as obtained from nmr experiments in chloroform. In aqueous solution the relaxation of atomic motion tends to be slower than in apolar solution.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360291214
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  • 6
    Electronic Resource
    Electronic Resource
    Conformation and formation tendency of the cyclotetrapeptide cyclo(D-pro-D-pro-L-pro-L-pro): Experimental results and molecular modeling studies (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 735-744 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound represents the smallest member of cyclic proline peptides corresponding to the general formula c(DDLL-Pro4)n with a strictly D, D, L, L double-alternating sequence of the chiral amino acid residues. The cyclopeptides with n ≥ 2 could be synthesized from both DDLL-Pro4 (1) and DLLD-Pro4 (2). The cyclic monomer (n = 1) resulted only from 2, whereas not even a trace could be found by cyclizntion of 1. The peptide exists in a strongly strained Ci symmetrical conformation (x-ray analysis) with alternating cis and trans peptide bonds (ctct form I). The cis peptide bonds deviate from planarity (ω = 22°); two of the pyrrolidine rings show a “South” conformation (φ = -94°), whereas the other residues exhibit Cα-endo puckering (φ = -124°). Two of the ψ angles surprisingly occur at +41° (anti-cis), the others are located in the trans′region. A quantitative ring opening occurs with trifluoroacetic acid at room temperature. In solution the existence of an isomeric ctcc sequence (form Ia) is indicated. Dreiding model studies also suggested a favorable conformation with a tctc sequence (form II). Consequently, we performed molecular mechanics calculations, based on the CHARMM force field and semiempirical quantum mechanical AMI calculations (MOPAC program). Pronounced differences in the backbone parameters were found using these two methods. However, the theoretical studies evidenced the experimentally obtained differences in the cyclization tendencies of the linear precursors.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310618
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  • 7
    Electronic Resource
    Electronic Resource
    Untersuchung des einflusses molekularer parameter auf morphologie und eigenschaften von polyethylenen niedriger dichte (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 187 (1991), S. 101-121 
    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: Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M̄w = 1.2 - 390·104 g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M̄w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M̄n, M̄w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal  -  for specific M̄w-ranges  -  strong changes and saturation ranges, resp., for the physical and application technological properties.
    Notes: Am Beispiel von PE-LD-Sorten und der durch präparative Fraktionierung gewonnenen Modellsubstanzen (Fraktionen im Molmassenbereich M̄w = 1,2 - 390·104 g/mol) wurden umfangreiche Untersuchungen zur Struktur-Eigenschaftsproblematik durchgeführt.Untersucht wurden die Korrelationen von M̄w mit 15 physikalischen und anwendungstechnischen Parametern unter Berücksichtigung der Reaktionsmechanismen bei der Herstellung von PE-LD im Rohr- und Rührautoklavreaktor, die zur Bildung der sogenannten primären Strukturparameter M̄n,M̄w, Molmassenverteilung, Kurzkettenverzweigung und Langkettenverzweigung führen. Bei der Interpretation der Ergebnisse wurden u. a. auch die morphologischen Gegebenheiten berücksichtigt, die im Zusammenhang mit den molekularen Parametern für bestimmte M̄w-Bereiche starke Ande-rungen bzw. Sattigungsbereiche für die physikalischen und anwendungstechnischen Eigenschaften erkennen lassen.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051870110
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  • 8
    Electronic Resource
    Electronic Resource
    Image enhancement of polyethersulfone ultrafiltration membrane surface structure for atomic force microscopy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 167-178 
    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 surface topography and pore structure of ultrafiltration membranes can be investigated with atomic force microscopy. In this study, it was found that the substitution of ethanol for water as the immersion medium improved the resolution of the fine structure of 10K polyethersulfone ultrafiltration membranes. Pores in the membrane surface from 7 to 9 nm in diameter were measured, which coincides with the range expected for 10,000 molecular weight cutoff (MWCO) ultrafiltration membranes. It is believed that this image enhancement results from increased damping and concomitant noise reduction resulting from the higher viscosity of ethanol in contrast to water.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460116
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  • 9
    Electronic Resource
    Electronic Resource
    Voltammetry in static and flowing solutions with a large-amplitude sine wave potential (1992)
    Weinheim : Wiley-Blackwell
    Electroanalysis 4 (1992), S. 429-437 
    Details
    ISSN: 1040-0397
    Keywords: Voltammetric detection ; sine wave potential ; digital filtering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Voltammetric detection is a potentially powerful method of detection for high performance liquid chromatography and flow injection analysis. A problem that needs a solution is its inferior detection limit compared to that obtained with amperometric detection. The shape of the potential waveform has been investigated in the search for methods of improving the detection limit of voltammetric detection. As a result, large amplitude sine wave potential perturbations have been found to give improved signal-to-noise ratios when compared to the values found for a corresponding triangle waveform (by a factor of from 1.1 to 5). This is principally due to the fact that the background current from a large amplitude triangle perturbation is spread over a wider frequency region. Signal processing techniques such as digital filtering have also been investigated. Digital bandpass filtering can be used to improve the signal to noise ratio by a factor of 2-13. Qualitative information (e.g., half-wave potential) is obtained through observing the phase angle at harmonics of the fundamental frequency.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140040408
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  • 10
    Electronic Resource
    Electronic Resource
    Zum Strömungsverhalten hochverdünnter wässeriger Tensid-Lösungen in geraden RohrenAuszugsweise vorgetragen von M. Weber auf dem GVC-Fachausschuß „Rheologie“am 16. Februar 1990 in Bad Honnef. (1991)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 63 (1991), S. 164-165 
    Details
    ISSN: 0009-286X
    Keywords: Strömungsverhalten ; Wärmeübergang ; Rohr ; Tensid-Lösungen ; Reibungsminderung ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330630231
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