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  • Polymer and Materials Science  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Approximate quantum-mechanical hamiltonians for slow internal rotations of macromolecules (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 479-488 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Slow internal rotations of three-dimensional macromolecules are studied based upon quantum mechanics, the Born-Oppenheimer approximation and related assumptions, and a variational inequality. Difficulties arising from vibrational and electronic energies are pointed out and bypassed consistently. Approximate quantum hamiltonians for internal rotations, in terms of dynamical variables studied recently, are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1994.040030215
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  • 2
    Electronic Resource
    Electronic Resource
    Approximate quantum-mechanical Hamiltonians for slow internal rotations of macromolecules (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 1127-1127 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1995.040040608
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  • 3
    Electronic Resource
    Electronic Resource
    Open three-dimensional unhindered molecular chains: Partition function (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 6 (1997), S. 1237-1261 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An open molecular chain, formed by N classical particles moving in three dimensions and having N - 1 bonds of constant lengths between successive neighbours, is considered. Hamiltonian methods with manifest rotational invariance allow to characterize all constraints. The classical partition function, Z0, for a large open chain in thermal equilibrium is analyzed in general. Simpler integral representations for Z0 are obtained, with the following advantages: (i) explicit rotational invariance in the integrands, (ii) only tridiagonal matrices appear and, moreover, approximations for their determinants can be obtained. For a two-dimensional open chain, an approximate factorized formula for Z0 is presented, and its essentials are generalized to the three-dimensional case. In both cases, the features of the partition functions bear certain similarities to that for a classical ideal gas. The approximate partition functions lead to approximate analytical computations of the correlations between pairs of different bond vectors, of the squared end-to-end distance, of the probability distribution for the end-to-end vector and of the structure factor, which display some novel features. Some comparisons with the corresponding results for the Gaussian chain are made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1997.040060612
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  • 4
    Electronic Resource
    Electronic Resource
    Modeling of butadiene polymerization using cobalt octoate/DEAC/water catalyst (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 655-673 
    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: Two-level fractional factorial designs were employed to study the solution polymerization of butadiene in a batch reactor using cobalt octoate/DEAC/water as catalyst. Conversion and molecular weight data obtained as functions of time were used to develop a kinetic model, and the estimated kinetic parameters were correlated empirically with four operating variables: temperature and concentrations of cobalt octoate, DEAC, and water. The experimental data indicate that at high water concentration a significant amount of oligomers is formed during early stages of polymerization, and the molecular weight of polymer increases with time. Analysis of the data suggests instantaneous initiation, first order propagation with cobalt and monomer, and transfer to monomer. Models which do not take account of the branching are shown to be incapable of fitting data for both Mn and Mw. The catalyst decay seems to follow a first-order mechanism, but the evidence is somewhat inconclusive.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360316
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  • 5
    Electronic Resource
    Electronic Resource
    Diacetylene-containing polymers, II. Polyesters and polyurethanes containing m,m′-butadiynylenedibenzyl groups (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 419-428 
    Details
    ISSN: 1042-7147
    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
    Notes: Diacetylene-containing polyesters and polyurethanes were prepared by the reaction of m,m-butadiynylenedibenzyl alcohol with isophthaloyl chloride, sebacoyl chloride, hexamethylene diisocyanate and 2,4-tolylene diisocyanate. Their thermal behavior was studied by optical microscope and differential scanning calorimetry (DSC). The polyesters were crystalline. The polyurethane prepared from hexamethylene diisocyanate and polyphthalates crystallized on cooling from their melts. All turned a reddish brown color on heating at temperatures above 200°C, and prolonged heating led to a black resin, but thermal decomposition could not be avoided. Irradiation by γ-ray and UV light at room temperature deepened the color of the films, but the polymerization of the diacetylene groups was not appreciable. Simultaneous heating and irradiation was necessary to obtain transparent, amorphous, wine red colored films.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030801
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  • 6
    Electronic Resource
    Electronic Resource
    Hindered macromolecular chains: A quantum mechanical model (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 7 (1998), S. 469-482 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A model for an open hindered three-dimensional macromolecular chain, based upon quantum mechanics, is proposed, which improves previous, work. The chain is formed by N particles (so that all bond lengths between successive particles take on given values) and harmonic-like vibrational potentials in the high-frequency limit constrain all successive bond angles. This formulation leads, via a variational procedure and a suitable choice of variables, to a specific quantum Hamiltonian for the chain. Issues related to overall rotational invariance are clarified. Some properties of the resulting classical partition function are analyzed. Several checks of consistency are given.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular chains with fixed bond lengths and angles: a study based on quantum statistical mechanics (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 367-395 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work studies large three-dimensional open molecular chains at thermal equilibrium in which bond lengths and angles are fixed (hard variables), based upon quantum statistics. A model for a chain formed by N particles interacting through harmonic-like vibrational potentials is treated in the high-frequency limit in which all bond lengths and angles become constrained, while other N angles (soft variables) remain unconstrained. The associated quantum partition function is bounded rigorously, using a variational inequality (related to the Born-Oppenheimer approximation), by another quantum partition function, Z. The total vibrational zero-point energy is shown to be independent of the soft variables thereby solving for this model a generic difficulty in the elimination of hard variables. Z depends only on soft variables and, under certain conditions, it can be approximated by a classical partition function Zc. The latter satisfies the equipartition principle and it differs from other classical partition functions for related molecular chains. The extension of the model when only part of the bond angles become fixed in the high-frequency limit is outlined. As another generalization, a systematic study of macromolecules, as composed of electrons and heavy particles with Coulomb interactions, is also presented. Its exact quantum partition function is bounded, supposing that the effective molecular potential also tends to constrain all bond lengths and angles, and under suitable assumptions, by another quantum partition function. The latter depends only on the remaining soft variables and it generalizes the one obtained for the first model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1995.040040211
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular chains with fixed bond lengths and angles: a study based on quantum statistical mechanics (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 1127-1127 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1995.040040609
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  • 9
    Electronic Resource
    Electronic Resource
    A quantum mechanical Hamiltonian for unhindered macromolecular chains: consistency with Gaussian models (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 7 (1998), S. 457-468 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A model for an open unhindered three-dimensional macromolecular chain, based upon quantum mechanics and proposed in previous works, is studied in order to investigate its physical properties and consistency. The chain is formed by N particles interacting through harmonic-like vibrational potentials in the high-frequency limit (in which all successive bond lengths become fixed). This formulation leads to a specific Hamiltonian for the chain: it constitutes an improvement in comparison with standard Gaussian models, which do not. The classical partition function Zc resulting from the quantum formulation is represented through an integral, which exhibits explicitly rotational invariance in the integrand and provides the basis for further approximations for large N. Approximate formulae are obtained for correlations between pairs of bond vectors, the distribution function for the end-to-end vector, distribution functions for individual bond vectors, “rubber eleasticity” (when stretching forces act) and the structure factor for small wave vector. In all cases, the results which have arisen from the quantum mechanical formulation coincide with those obtained for the standard Gaussian chain. This agreement appears to confirm the physical consistency of the quantum Hamiltonian characterizing the model.
    Type of Medium: Electronic Resource
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