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  • 1
    Electronic Resource
    Electronic Resource
    Influence of counterion valency on the scattering properties of highly charged polyelectrolyte solutions (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3299-3313 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Light and neutron scattering measurements on highly charged polyelectrolyte solutions have recently provided firm evidence for the existence of "domain structures" containing many chains, even at rather low-polymer concentrations. In the present paper, we systematically investigate the influence of counterion charge valency Zc on the scattering properties of sulfonated polystyrene (PSS) solutions in water with monovalent and divalent counterions. This study is part of a larger effort to identify essential factors governing polyelectrolyte domain formation and the geometric properties of these transient structures. Neutron scattering measurements indicate that the interchain correlation length ξd within the domains becomes larger by a factor of 1.5–2 for divalent relative to monovalent counterions. This observation is consistent with the Manning model estimate of the change in effective polymer charge density Γ* with Zc and with previous observations linking ξd [from the peak position in the scattering intensity [I(q)] with the bare polymer charge density, Γ. Light scattering measurements of the radius of gyration Rg,d of the domains indicate that their size becomes smaller for divalent counterions and with a reduction of Γ. We observe that the "fractal" dimension of the domains measured from the low-angle scaling of I(q) depends on the chemical structure of the polyelectrolyte. Zero average contrast (ZAC) neutron scattering measurements show that the radius of gyration Rg,c of individual polyelectrolyte chains is also reduced for divalent counterions, suggesting that chain rigidity is strongly influenced by Γ*. Charge valency effects on relaxation times are investigated by dynamic light scattering. As usual, two diffusive modes are observed in the light intensity autocorrelation function, G(τ). The "fast" mode becomes slower and the "slow" mode becomes faster for the divalent counterion (Mg2+), relative to the monovalent counterion (Na+). Counterion valence has a large influence on the structure and dynamics of highly charged polyelectrolyte solutions through its influence on Γ*. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1336148
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  • 2
    Electronic Resource
    Electronic Resource
    Formation and dissolution of phase-separated structures in ultrathin blend films (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 191-200 
    Details
    ISSN: 0887-6266
    Keywords: ultrathin films ; polymer blends ; phase separation ; atomic force microscopy ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase separation of ultrathin polymer blend films of deuterated poly(styrene)/poly(vinylmethylether) leads to a variety of film morphologies, depending on polymer composition. Phase-separation measurements are made at a constant temperature difference from the critical temperature, leading to a bicontinuous spinodal decomposition pattern for near-critical blend compositions and to “mounds” and “holes” for PVME-rich and dPS-rich off-critical mixtures, respectively. Reverse temperature jumps of the phase-separated blend films into the one-phase region result in dissolution of the undulating surface patterns, confirming the phase-separation origin of the film patterns. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 191-200, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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