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  • Polymer and Materials Science  (2)
  • Atomic, Molecular and Optical Physics  (1)
  • Computational Chemistry and Molecular Modeling  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Tunneling phenomena in three-dimensional double-well potentialsResearch Supported in part by a grant from the National Science Foundation. (1973)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 7 (1973), S. 319-332 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tunneling of a hydrogen atom through the barrier of a three-dimensional double-well potential is considered. From the time-dependent Schrödinger equation, expressions are derived for the ensemble-averaged probability density and for the probability that the hydrogen atom is in the reactant region, in the barrier region, or in the product region. It is found that when thermal vibrations are not taken into account, the ensemble-averaged probability density may oscillate with time about its equilibrium value. When thermal vibrations are included, the oscillations become damped and the probability density approaches equilibrium. The tunneling rate is found to decrease considerably for increasing barrier thickness and barrier height.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560070214
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  • 2
    Electronic Resource
    Electronic Resource
    Equation of state predictions of sorption isotherms in polymeric materials (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1781-1795 
    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 ability of the Sanchez-Lacombe equation of state to predict the solubility of small penetrants in rubbery polymer matrices, over a wide range of ambient pressures, is examined critically. The solute chemical potential and, in turn, the resulting predicted isotherms are found to depend strongly on solute equation of state parameter values and on the mixing parameter for polymer-penetrant interactions. The isotherms are less sensitive to polymer equation of state parameters. In the sorption of organic vapors into polymers, the model does not describe well the sorption isotherms at high values of penetrant activity. The model appears to describe sorption isotherms most accurately when both polymer and penetrant equation of state parameters are determined from pure component properties, in the same temperature and pressure range as the sorption data, and when a mixing parameter is used to adjust the fit of the model to the data. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070501014
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  • 3
    Electronic Resource
    Electronic Resource
    Transport of swelling penetrants in glassy polymers: Influence of convection (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 3627-3647 
    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 transport of a solute by diffusion into a glassy polymer can lead to swelling of the material. For certain types of polymers, a sharp interface is formed between the swollen region and the glassy core. When the density of the swollen material is much smaller than the density of the glass, a significant convective mass-average velocity is generated within the sample. Previous models have neglected the role this convection plays in solute transport and in the proper calculation of the sample dimensions as a function of time. In this paper, we study the contribution of convective terms to the solute transport process, including the motion of the swollen polymer/solution interface. We also compute the eulerian strains that result from the calculated velocity fields and the stresses that would be generated if a linear viscoelastic model is used as a constitutive equation relating the stress to the strain. We show that serious errors can be generated in the calculations if convective terms are neglected. Furthermore, a comparison of the strains and stresses acting on the polymer with those acting on the mixture of solute and polymer shows that they can be significantly different. The stresses and strains acting on the polymer alone offer the most rational physical picture of the material deformation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070320219
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