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  • 1
    Electronic Resource
    Electronic Resource
    Matrix-assisted laser desorption/ionization mass spectrometry of synthetic polymers. 3. Analysis of condensation polymers (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 241 (1996), S. 95-111 
    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 matrixunterstützte Laser-Desorptions/Ionisations-Massenspektrometrie ist eine leistungsfähige Methode zur Analyse von Kondensationspolymeren. Obwohl diese Produkte eher niedermolekular sind, weisen sie eine komplexe chemische Struktur auf. Phenol-Novolake und -Resole können bezüglich des Polymerisations grades und des Typs und der Anzahl der funktionellen Gruppen analysiert werden. Modifizierte Phenolharze, wie epoxidierte Novolake, können identifiziert und der Epoxidierungsgrad bestimmt werden. Für Polycarbonate und Polyester wird gezeigt, daß in Abhängigkeit vom Reaktandenverhältnis lineare Oligomere mit unterschiedlichen Endgruppen und cyclische Oligomere gebildet werden.
    Notes: Matrix-assisted laser desorption/ionization mass spectrometry is shown to be a suitable method for the analysis of condensation polymers. Although these products are rather low in molar mass, they exhibit a complex chemical structure. Phenolic novolacs and resols can be analysed with respect to the degree of polymerization and the type and number of functional groups. Modified phenolic resins, such as epoxidized novolacs, can be identified and the degree of epoxidation can be determined. It is shown for polycarbonates and polyesters that depending on the reactant ratio linear oligomers with different endgroups and cyclic oligomers are formed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052410108
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular modelling of polymers, 1. Prediction of critical values of oligomethylenes (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 983-989 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Most procedures for the estimation of critical values of oligomethylenes assume these critical values to depend only on the chain length n and/or the molecular weight M. In this work, we introduce new equations for estimating the critical values by inclusion of quantum chemical data calculated by a semiempirical SCF-MOSCF-MO: Self-consistent field, molecular orbital. method (AM1). These models give a much superior prediction for the critical values such as the normal boiling point Tb, critical temperature Tc, critical pressure Pc, critical valume Vc, surface tension yb and enthalpy of vaporization ΔHvp of 18 oligomethylenes. The predictions for polyethylene (with infinite chain length) for the values of Tb, Tc, Pc, Vc, ΔHvp and yb are 1029.3 K, 1029.3 K, 1.013 bar, 15723.3 m3/mol, 0 KJ/mol and 0 mN/m, respectively.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1995.040040510
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of Li+, Na+, Mg2+, Ca2+, and Zn2+ ions on the hydrogen bonds of the Watson-Crick base pairs (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 757-769 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of mono- and divalent metal ions with the nucleic acid base pairs A:T and G:C has been studied using ab initio self-consistent field Hartree-Fock computations with minimal basis sets. Energy-optimized structures of the two base pairs with a final base-base distance of L = 10.35 Å have been determined and were further used in calculations on ternary complexes Mn+ - A:B together with previously computed coordination geometries of the cations at adenine (Ade), thymine (Thy), and guanine (Gua). Besides the binding energy of the various metal ions to the base pairs, changes in the stability of the H bonds between Ade and Thy or Gua and Cyt have been determined. Polarization effects of the metal ion on the ligand turned out to increase the binding between complementary bases. Regardless of the metal species, cation binding to Gua N(3) and Thy O(2) leads to a special increase in H-bond stability, whereas binding to Ade N(3) changes the H-bond stability least. Situated in between are the stabilizing effects caused by Gua and Ade N(7) coordination. A remarkable relation between the stability of the H bond and the distance from metal binding site to H bonds was found. This relationship has been rationalized in terms of partial charges of the atoms participating in H bonding, which can reveal the trend in the electrostatic part of total H bond energy. It can be shown that a short distance between coordination site and acceptor hydrogen increases the H-bond strength substantially, while a long distance shows minor effects as supposed. On the other hand, the opposite effect is observed for the influence of the distance between binding site and donor atom. A comparison of our findings with a new model of transition metal ion facilitated rewinding of denatured DNA proposed by S. Miller, D. VanDerveer, and L. Marzilli is given [(1985) J. Am. Chem. Soc. 107, 1048-1055].
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290410
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  • 4
    Electronic Resource
    Electronic Resource
    Chromatographic investigations of macromolecules in the critical range of liquid chromatography, 10Part 9: cf. ref.13.. Polymer blend analysis using a viscosity detector (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 2691-2701 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Binary polymer blends were separated by liquid chromatography at the critical point of adsorption. By operating at chromatographic conditions corresponding to the critical point of one blend component, the blends were separated regardless of the molar mass distributions of the components. After the separation step both components were precisely detected by an on-line capillary viscometer. In contrast to refractive index detection, where a strong solvent peak appears in most cases, the viscosity signal is not affected by sight deviations in the mobile phase composition. Under critical conditions of adsorption of one component both blend components exhibit normal Mark-Houwink behaviour. Therefore, the viscosity detector in conjunction with a concentration detector can be used for determining the molar mass distribution of both blend components.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1996.021970908
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  • 5
    Electronic Resource
    Electronic Resource
    The melting points of oligomethylenes (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2139-2143 
    Details
    ISSN: 0887-6266
    Keywords: quantum chemistry ; CNDO/2 ; oligomethylene ; polyethylene ; melting point ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Quantitative structure-property relationships (QSPR) between the melting points of oligomethylenes and quantum chemical data calculated by the semiempirical method CNDO/2 were investigated. A linear relationship between the average net charges of hydrogen and carbon atoms in the molecules and the melting points could be established, achieving good fit as well as predictability. Further, the relation between the net charges and the chain length was evaluated. The evaluated net charges of polyethylene lead to a calculated melting point of 141.4°C (experimental: 141.4°C). © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular modelling of polymers, 3Part 1: cf. ref.36 Part 2: T. T. M. Tan, B. M. Rode, J. Appl. Polym. Sci., submitted.. Prediction of glass transition temperatures of poly(acrylic acid), poly(methacrylic acid) and polyacrylamide derivatives (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 5 (1996), S. 467-475 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The establishment of the relations between the glass transition temperatures of polymers, such as poly(acrylic acid), poly(methacrylic acid), polyacrylamide and their derivatives, and the electronic structure of their monomers calculated by various methods such as the quantum chemical methods AM1 and PM3, and the Gasteiger-Hückel method has been investigated. Partial charges of some important atoms in the monomer together with the degree of substitution and chain length of the hydrocarbon group of ester or amide functions of the monomer were used as descriptors. The results indicate that the quantum chemical methods PM3 and especially AM1 lead to models of superior predictability compared to the one obtained by the Gasteiger-Hückel method.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1996.040050306
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and properties of self-protecting polyarylates (1969)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 7 (1969), S. 157-172 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Self-protective polyesters were synthesized in two ways: by polymer analog transformations on polymers obtained and by introduction of inhibiting groups into the polymer during synthesis. It is shown that the Fries rearrangement takes place in the aromatic polyesters in the presence of the Friedel-Crafts catalysts and on ultraviolet irradiation as well. Thermogravimetric analysis of the rearranged polymers and investigations of the influence of the ultraviolet irradiation on their properties show that the rearrangement markedly increases the photochemical and thermal stability of the polymers. Photostabilization may also be accomplished by the introduction of inhibiting groups, such as hydroxyl, sulfur, or phosphorus into the polymer molecule.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1969.150070114
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  • 8
    Electronic Resource
    Electronic Resource
    Thermostability of some isomeric polyoxadiazoles (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 6 (1968), S. 1351-1365 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal stability of the isomeric poly-1,2,4-oxadiazole (PO-2) and poly-1,3,4-oxadiazole (PO-3) was investigated. The isomerism of the ring substantially influenced polymer thermostability. The weight losses in PO-2 occur above 220-230°C. in vacuo, but PO-3 degrades only at 280-300°C. The weight changes in isomeric polyoxadiazole at lower temperatures are connected with the completion of the cyclization process. At higher temperatures degradation of the oxadiazole ring takes place, and as a result carbon and nitrogen oxides, 4,4′-dicarboxy (diphenyl ether) dinitrile and other products are evolved. The mechanism of polymer thermal degradation is examined; it is shown that the weakest bonds are C—O and N—O. These data are in a good agreement with the results of calculation of the π-electron systems of unsubstituted oxadiazole cycles in the framework of the molecular orbital treatment in the Hückel approximation. It is shown that the oxygen in the oxadiazole ring oxidizes the products of thermal degradation of polymers and a cell effect takes place. The thermal oxidation of isomeric polyoxadiazoles does not differ essentially from the degradation in vacuo. It was found that the formation of intermediate products such as peroxides and hydroperoxides does not take place, and oxygen does not act as an initiator of polymer degradation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1968.150060526
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