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  • 1
    Electronic Resource
    Electronic Resource
    Configurations of liquid crystalline polymers in nematic solvents (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 11117-11128 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have considered the effect of a nematic solvent on the configurations of liquid crystalline polymers (LCPs) modeled as semiflexible chains. The model for the chain is a generalization of the Kratky–Porod model satisfying the global inextensibility of the chain for all values of coupling with the nematic field. We have calculated analytically the components of the mean-square end-to-end distance, persistence length and radius of gyration parallel and perpendicular to the nematic director, and the asymptotic behaviors of the structure factor. We also discuss the effect of architecture on the configurations of the polymer. We conclude that the configurations of main-chain and side-on side-chain LCPs are more sensitive to the nematic solvent than those of end-on side-chain LCPs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477750
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  • 2
    Electronic Resource
    Electronic Resource
    Attractive interactions and phase transitions in solutions of similarly charged rod-like polyelectrolytes (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 1765-1777 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have calculated the effective interaction and thermodynamic behavior of semidilute solutions of rod-like polyelectrolytes. The model is based on a bare potential energy constructed from the Debye–Hückel potential but extended to include the anisotropic contributions arising from the rod-like conformation. We have calculated the bare and effective potential energy between two Kuhn segments in different polyelectrolyte rods, the isotropic-to-nematic transition, the orientational order parameter of the nematic phase and the phase diagram of the system. Moreover, the effects of molecular weight, monomer, and salt concentration on the different quantities are discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479438
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  • 3
    Electronic Resource
    Electronic Resource
    Configurational properties of a single semiflexible polyelectrolyte (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 4367-4375 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using a variational calculation, we have considered the effect of chain length, intrinsic backbone stiffness, solvent quality, and salt concentration on the behavior of a single semiflexible polyelectrolyte in dilute solution. Explicitly, we have calculated the radius of gyration (Rg) and effective persistence length for different solvent qualities and salt concentrations. For an isolated semiflexible polyelectrolyte with increasing molecular weight, there can be five regimes with effective exponent ν (defining the molecular weight dependence of Rg) being 1, 1/2, 1, 2/5, and 1/2 in the absence of nonelectrostatic excluded volume interaction. This suggests a double crossover behavior from rodlike to Gaussian and then to Gaussian again as the chain length is increased. During the second crossover, ν can be as high as 1, although the actual value of Rg is order of magnitude smaller than the rodlike value. There can be another regime in this second crossover where the apparent exponent is 2/5 due to additional self-screening arising from counterions of the polymer. This self-screening can significantly reduce Rg, although the asymptotic exponent 2/5 may not be observable due to physical constraints. A thorough analysis of the crossover behavior is presented. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1386924
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  • 4
    Electronic Resource
    Electronic Resource
    Mapping of the relaxation patterns of polymer melts with linear flexible molecules of uniform length (1997)
    Springer
    Rheologica acta 36 (1997), S. 330-344 
    Details
    ISSN: 1435-1528
    Keywords: Relaxation time spectrum ; monodisperse polymers ; hypergeometric function ; incomplete gamma function ; linear viscoelasticity ; polymer dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The linear viscoelastic material functions of linear flexible polymers of uniform length are calculated from the BSW spectrum (Baumgaertel et al., 1990, 1992), and explicit analytic expressions are presented for several of the most common material functions for transient and dynamic experiments. However, numerical calculations are presented whenever needed. The BSW spectrum was determined from experimental G″, G″ data of two sets of molten polymers of narrow molecular weight distribution, polystyrene and polybutadiene. The purpose of the mapping is to show a wide range of viscoelastic behavior which otherwise is not available in such comprehensive form. Experimental check of these predictions is still needed in most cases. Also, some insight into the predictions for the non-linear (including the non-equilibrium) viscoelastic behavior is achieved by studying two particular experiments: the start-up of uniaxial extension at constant rate and the start-up of shear flow at constant rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366674
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  • 5
    Electronic Resource
    Electronic Resource
    Mapping of the relaxation patterns of polymer melts with linear flexible molecules of uniform length (1997)
    Springer
    Rheologica acta 36 (1997), S. 330-344 
    Details
    ISSN: 1435-1528
    Keywords: Key words Relaxation time ; spectrum ; monodisperse polymers ; hypergeometric function ; incomplete gamma function ; linear viscoelasticity ; polymer dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The linear viscoelastic material functions of linear flexible polymers of uniform length are calculated from the BSW spectrum (Baumgaertel et al., 1990, 1992), and explicit analytic expressions are presented for several of the most common material functions for transient and dynamic experiments. However, numerical calculations are presented whenever needed. The BSW spectrum was determined from experimental G′,G″′ data of two sets of molten polymers of narrow molecular weight distribution, polystyrene and polybutadiene. The purpose of the mapping is to show a wide range of viscoelastic behavior which otherwise is not available in such comprehensive form. Experimental check of these predictions is still needed in most cases. Also, some insight into the predictions for the non-linear (including the non-equilibrium) viscoelastic behavior is achieved by studying two particular experiments: the start-up of uniaxial extension at constant rate and the start-up of shear flow at constant rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366674
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  • 6
    Electronic Resource
    Electronic Resource
    Free volume, hole theory and thermal properties (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2645-2651 
    Details
    ISSN: 0887-6266
    Keywords: van der Waals free volume ; hole theory ; thermal properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Free volume ideas have been employed extensively in the interpretation of equilibrium processes and as a measure of molecular mobility. More recently, the vacancy fraction h, defined in our hole theory, has served to provide a link between diverse processes. This raises a question regarding the relation between the van der Waals type of free volume and h. As an important and useful result, valid for polymers and low molar mass fluids, simple relations are obtained between the van der Waals volume Vw, computed according to Bondi's structural rules, and the scaling volume V* in the hole theory. This is defined by the intersegmental potential and extracted from the equation of state. In turn, this result enables us to compute the corresponding scaling temperature T*. In this manner the theory predicts the volume-temperature function for a melt, based on a single experimental datum. Corresponding considerations are presented for the glassy state. The quantitative relation between the van der Waals type of free volume vf and h derived makes it possible to reconsider various empirical correlations involving the former. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321610
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  • 7
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    Coupling Between Adsorption and the Helix-Coil Transition (1999)
    American Physical Society
    Details
    Publication Date: 1999-06-28
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 8
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    Stretching Helical Semiflexible Polymers (2005)
    American Chemical Society
    Details
    Publication Date: 2005-02-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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  • 9
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    A Minimal Model for the Helix−Coil Transition of Wormlike Polymers. Insights from Monte Carlo Simulations and Theoretical Implications (2004)
    American Chemical Society
    Details
    Publication Date: 2004-11-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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  • 10
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    Coupling between Helix-Coil and Coil-Globule Transitions in Helical Polymers (2005)
    American Physical Society
    Details
    Publication Date: 2005-10-12
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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