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  • Polymer and Materials Science  (120)
  • 1980-1984  (120)
  • 1950-1954
  • 1981  (120)
  • 1
    Electronic Resource
    Electronic Resource
    The active centres in the anionically activated polymerization of ε-caprolactam (1981)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 32 (1981), S. 31-35 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Conductometric investigations with solutions of Na-ε-caprolactam (catalyst of the activated anionic polymerization) in the caprolactam melt in the presence of N-acetyl-ε-caprolactam, dibenzo-18-crown-6 and sodium tetraphenyl borate are described. Based on conductometric and kinetic results the activated anionic polymerization of ε-caprolactam is shown to proceed at free anions as well as at ion pairs. The possibility of the polymerization of the monomer by the ionic coordination mechanism is considered.
    Notes: Konduktometrische Untersuchungen an Lösungen des Na-ε-caprolactams (eines Katalysators der aktivierten anionischen Polmerisation) in der Caprolactamschmelze in Gegenwart von N-Acetyl-ε-caprolactam, Dibenzo-18-crown-6 und Natriumtetraphenylborat werden beschrieben. Anhand der konduktometrischen und kinetischen Untersuchungen wird gezeigt, daß die aktivierte anionische Polymerisation von ε-Caprolactam sowohl an freien Anionen als auch an Ionenpaaren verläuft. Die Möglichkeit der Polymerisation des Monomers nach dem ionischen Koordinationsmechanismus wird betrachtet.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1981.010320108
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  • 2
    Electronic Resource
    Electronic Resource
    A study of structure formation processes occurring with the gelation of polysulfonamide solution in dimethylacetamideProofs received from author March 12, 1981 (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 1197-1202 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work investigates spontaneous gelatination of polysulfonamide in the solution of dimethylacetamide by nuclear magnetic relaxation, small-angle light scattering, and refractive index measurement. Two stages of the gelatination process were found to occur. Spherulites are formed in the first stage while the mobility of the solvent molecules decreases sharply. The second stage is characterized mainly by perfection of the inside structure of spherulites without a change in their size. The degree of decreasing mobility of the solvent molecules is much less in this stage than in the first stage.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190515
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetische Besonderheiten der Kristallisation von Polycaproamid bei der anionischen adiabatischen Polymerisation (1981)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 32 (1981), S. 440-444 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The kinetics of adiabatic crystallization of polycapromide is studied during the anionic activated polymerization of ε-caprolactam with the initial temperatures of the synthesis in the range from 110°C to 150°C. The morphology of the polymer develops via formation of coarse spherulitic aggregates and their subsequent division. An important role of the secondary crystallization is emphasized by which a perfectionation of the spherulites occurs followed by formation of a uniform fine-spherulitic structure.
    Notes: Die Kinetik der adiabatischen Kristallisation des Polycaproamids im Verlaufe der anionisch aktivierten, bei Anfangstemperaturen von 110°C bis 150° C ablaufenden Polymerisation des ε-Caprolactams wurde untersucht. Die Ausbildung der Morphologie des Polymers erfolgt über ein Stadium der Bildung großer sphärolitischer Aggregate und ihrer anschlißenden Zerstückelung. Wichti ist die Sekundärkristallisation, bei der die endgültige Ausbildung der Sphärolithe und die Bildung der homogenen, kleinsphärolitischen Struktur erfolgen.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1981.010320802
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  • 4
    Electronic Resource
    Electronic Resource
    Three-dimensional structure of actinoxanthin. III. A 4-Å resolution (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 679-694 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The protein actinoxanthin (molecular weight 10,300) crystallizes in space group P212121, with cell dimensions a = 30.9 Å, b = 48.8 Å, c = 64.1 Å, and z = 4. The three-dimensional structure of actinoxanthin at 4-Å resolution was determined by x-ray methods on the basis of experimental data from the native protein and five isomorphous derivatives. At the stage of solving the phase problem, the heavy atoms in the derivatives were located using direct methods. The actinoxanthin molecule can be described as an oblate ellipsoid with approximate dimensions 20 × 30 × 40 Å and consists of two different sizes of folded units separated by a well-defined cleft. The larger unit, including the N- and C-terminals of the protein chain, is characterized by a significant content of β-sheet structure. The smaller unit, containing two deca- and hexapeptide cycles closed by disulfide bonds, has a mainly irregular structure.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1981.360200405
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  • 5
    Electronic Resource
    Electronic Resource
    Synthese von Polybutylenterephthalat: Dichte der Monomere und Reaktionsgemische (1981)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 32 (1981), S. 282-284 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1981.010320511
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  • 6
    Electronic Resource
    Electronic Resource
    Simulation of conformational possibilities of DNA via calculation of nonbonded interactions of complementary dinucleoside phosphate complexes (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 1-15 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using classical potential functions, we carried out potential-energy calculations on the complementary deoxydinucleoside phosphate complexes dApdA:dUpdU, dUpdA:dUpdA, and dApdU:dApdU. All dihedral and bond angles, except those of the nitrogen bases, were varied. The resulting minimum-energy conformations of the complexes are close to DNA A- and B-family conformations, with a typical arrangement of the nitrogen bases. The dihedral and bond angles of one of the molecules forming the complex can thereby differ by several degrees from those of the other molecule. For different base sequences, some dihedral and bond angles may vary over a range of several degrees without appreciably changing the total energy of the complex. Some low-energy conformations of the complexes corresponding to other regions of the conformational space are also found. The biological consequences of possible changes in dihedral and bond angles, occurring on interaction with other molecules, are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1981.360200102
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  • 7
    Electronic Resource
    Electronic Resource
    Catalytic behaviour of metalcomplexes immobilized in functional polymeric carriers (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 5 (1981), S. 121-154 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The general principles of construction of gel-immobilized catalyst systems (GICS) are reported as well as some peculiarities of the polymerization of ethylene and of the dimerization of ethylene and propylene in the presence of these systems.GICS consist of a transition metal complex and a specially designed polymeric support. Advantages offered by gel-immobilized catalyst systems are discussed with respect to homogeneous and microheterogeneous metal complex catalysts.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.020051981109
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  • 8
    Electronic Resource
    Electronic Resource
    Polarized luminescence and mobility of tryptophan residues in polypeptide chains (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 2287-2309 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polarized luminescence was used to study the mobility of tryptophan residues in polypeptide chains of different chemical composition and structural organization. It has been shown that the luminescence depolarization of tryptophan residues in coillike, helical, and β-structural polypeptide chains is mainly caused by “fast” torsional vibrations and “slow” rotational isomerization of indole groups of tryptophan side chains. The characteristics of these types of motions are practically the same for tryptophan residues included in coillike chains of different chemical structure. Helix-coil transitions in copolymers of glutamic acid and lysine with tryptophan (Glu, Trp) and (Lys, Trp) (where side groups of tryptophan residues weakly interact with the surrounding side groups) do not appreciably change the amplitude of torsional vibrations or rotational isomerization. At the same time, in the helical state of glutamic acid-leucine-tryptophan copolymers (Glu, Leu, Trp) and in the β-structural state of (Lys, Trp) copolymers (where direct interactions of Trp side groups with other side groups are possible), the amplitudes of the torsional vibrations are smaller and the rotational isomerization times larger than in the coil. The transition of (Glu, Leu, Trp) polypeptide chains into a compact state is accompanied by a marked decrease of both “fast” and “slow” intra-molecular mobility and by an increase of the contribution made by the rotation of the macromolecule as a whole, as shown by the decrease of the luminescence polarization.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1981.360201102
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  • 9
    Electronic Resource
    Electronic Resource
    The heterogeneous structure of polyurethane networks (1981)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 100 (1981), S. 99-115 
    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: Mit Hilfe der Röntgenkleinwinkelstreuung wurde die mikroheterogene Struktur von vernetzten amorphen Polyurethanen untersucht. Es wurde gezeigt, daß diese Struktur von den Eigenschaften der eingesetzten oligomeren Diole abhängt. Je nach Molekulargewicht der Oligomeren bleibt die ursprüngliche Struktur der Oligomeren mehr oder weniger erhalten. Dieser Effekt ist für Polyoxypropylenglykol mit einem Molekulargewicht von 2000 g/mol stärker ausgeprägt als bei einem Molekulargewicht von 500 g/mol. Bei Oligomeren mit kleinem Molekulargewicht üben die steifen Bruchstücke in den Vernetzungsgebieten aufgrund der hohen Konzentration an Wasserstoffbindungen einen großen Einfluß auf die Struktur aus. Hier wurde eine Abnahme der Heterogenität festgestellt. Die heterogene Struktur der vernetzten Polyurethane wird mit dem Ansteigen der oligomeren Kettenlänge und des Umsetzungsgrades deutlicher. Alle beobachteten Effekte lassen sich mit der Änderung des Vernetzungsgrades der Netzwerkabschnitte erklären.
    Notes: Using small-angle X-ray scattering the microheterogeneous structure of amorphous polyurethane networks was investigated. It was found to be determined by the corresponding structural characteristics of the initial oligomeric diols. The structure of the oligomers is preserved more or less depending on their chain length in polymeric networks (poly(oxypropyleneglycol) with molecular weights of 2000 and 500 g/mol, resp.). In the latter case a great influence on the structure is exerted by rigid fragments around crosslinks which are characterized by great concentrations of H-bonds. This is leading to a decrease in the heterogeneity. The heterogeneous structure of the polyurethane networks becomes more distinct with an increase in the oligomer chain length and degree of conversion. The observed effects are explained by the change in the degree of aggregation of parts of the network structure.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1981.051000106
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  • 10
    Electronic Resource
    Electronic Resource
    Biodegradation of gelatin-g-poly(ethyl acrylate) copolymers (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 3633-3641 
    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: Gelatin-g-poly(ethyl acrylate) copolymers were prepared in an aqueous medium, using K2S2O8 initiator. The composition of the graft copolymers was dependent upon temperature and duration of the reaction. The number of grafting sites was small and molecular weight of the grafted poly(ethyl acrylate) branches was high. Three copolymer samples with grafting efficiencies of 33.3%, 61.0%, and 84.0%, were tested for their microbial susceptibility in a synthetic medium employing a mixed inoculum of Bacillus subtilis, Pseudomonas aeruginosa, and Serratia marcescens and the percent weight losses were 12%, 10.1%, and 6.0%, respectively, after 6 weeks of incubation. The extent of degradation seems to decrease with increasing grafting efficiency. There was initial rapid weight loss accompanied by the exponential increase in bacterial population and pH of the culture medium during the first week. The nitrogen analysis also showed the utilization of the polymer. A parallel set of experiments, carried out by employing the samples as the only source of both carbon and nitrogen, showed a marginal but definite increase in the utilization of the polymer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070261111
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