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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 87 (1983), S. 2881-2889 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3305-3317 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have studied the phase separation behavior of polymer solutions in two-dimensional elongational flows that are sufficiently weak to avoid the coil–stretch transition. On the basis of a simple model that neglects hydrodynamic interactions, we find no shifts in the infinite molecular weight θ point, or coexistence curve. For finite chain lengths, there are flow-induced shifts of both quantities. These shifts are calculated to leading order in a loop expansion and are found to be order (Sζ)2N7/2, where S is the extension rate, ζ is the monomer friction coefficient, and N is the degree of polymerization. Our results are in qualitative agreement with experimental observations that find demixing promoted by flow.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5890-5897 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mode coupling and fluctuation effects on the low frequency linear viscoelastic properties of homogeneous diblock copolymers are investigated. Attention is restricted to temperatures near, but not below the microphase separation transition (MST), where a homogeneous block copolymer melt first transforms to a spatially periodic, compositionally inhomogeneous morphology. We find that long-wavelength transverse momentum fluctuations couple only weakly to compositional order parameter fluctuations; the latter are predominantly on the scale of the radius of gyration. Crossover expressions are obtained for the renormalized transport and viscometric coefficients. The fluctuation contributions to these various coefficients are smaller than originally predicted at the MST, a consequence of refined calculations showing the MST to be a weakly first order phase transition.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2048-2061 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a field-theoretic treatment of polymer solution dynamics. The method involves the construction of a Martin–Siggia–Rose generating functional for flexible polymer chains dissolved in a low molecular weight solvent. This formalism is shown to be particularly convenient for investigating the dynamics of collective field variables, such as polymer concentration or elastic stress. Moreover, it provides an extension to nonequilibrium phenomena of Edwards' conjugate field approach to the static properties of semidilute polymer solutions. The theory is amenable to conventional field-theoretic approximation methods. We explicitly investigate a Gaussian approximation, which gives concentration correlation and response functions identical to those obtained from the dynamical random phase approximation. However, the method also demonstrates screening of hydrodynamic disturbances, the crossover to macroscopic hydrodynamics, and provides information on elastic stress dynamics. We expect that the advantages of the present formalism will become most apparent far from equilibrium, such as in the description of flow-induced fluctuations and phase separation of polymer solutions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7200-7208 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements of the interfacial tension γ between immiscible polymers of low molecular weight have not resolved the question of how γ depends on the degree of polymerization N. In this paper the issue is addressed theoretically by solving equations derived earlier, but previously solved only in the infinite molecular weight limit. The basic origin of molecular weight dependence is entropic adsorption of chain ends to the interfacial region. It is found that the interfacial tension and concentration profile across the interface approach the infinite degree of polymerization limit like N−1. No sign is found of the N−2/3 approach reported to fit the data, although not unambiguously. If correct, N−2/3 may be a law applicable over a limited range, and not asymptotically.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 20 (1987), S. 822-829 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 8 (1975), S. 552-556 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 18 (1985), S. 1157-1162 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Accounts of chemical research 8 (1975), S. 295-299 
    ISSN: 1520-4898
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 697-705 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of composition fluctuations on the microphase separation transition in diblock copolymers is investigated. Such fluctuation corrections, which were neglected in the mean field treatment of Leibler, are found to be significant for the molecular weights usually encountered. The analysis is facilitated by reducing the block copolymer Hamiltonian to a form previously studied by Brazovskii. Our principal results are the following: (i) A symmetric diblock copolymer is predicted to undergo a first order phase transition at a larger value of χN than the second order transition found by Leibler. The Flory interaction parameter is denoted χ and N is the number of statistical segments per chain. The location of the transition is predicted to be at (χN)t=10.495+41.022 N−1/3, where the peak in the scattering function attains its maximum value of 0.12328 N1/3. (ii) We find windows in composition, with finite width, through which it is possible to pass from the disordered phase to each of the ordered microphases (lamellar, hexagonal, and body-centered-cubic) by changing temperature. (iii) All the results of Leibler are recovered in the limit of block copolymers with infinite molecular weight.
    Type of Medium: Electronic Resource
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