Abstract
Quasi-Elastic light scattering experiments have been performed on aqueous solutions of sodium poly(styrene sulfonate) (Mw=3.5×105 g mol−1) in the ionic strength range of 0.005 to 2 M at T=20°C. The angular dependence of the apparent diffusion coefficient was analyzed within the framework of the Fujime-Maeda theory for semifiexible rods. At zero polyion concentration both the overall translational and the rotational diffusion coefficient increase with the ionic strength, while the difference between the translational diffusion coefficients perpendicular and parallel to the rod axis decreases. The molecular structure of a PSS-polyion is also quite well described by the model of a wormlike prolate ellipsoid, where the ratio of the minor to the major semiaxis rises from 0.29 at low ionic strength (I=0.005 M) to 1 at the θ-state. By solving the Poisson-Boltzmann equation we have determined the effective polyion charge, Zeff, that is not neutralized by the small ions at a distance r=dh/2 from the PSS-skeleton, where dh is the hydrodynamic diameter of the polyion. It is found: (1) Zeff is independent of the ionic strength; and (2) Zeff is much smaller than the corresponding Z-values obtained from dialysis equilibrium experiments. The reason for this discrepancy is clear. The dialysis technique yields the surface charge of the polyion, while transport techniques such as diffusion experiments yield the effective charge, Zeff. The latter incorporate hydrodynamic and electrostatic coupling forces acting between the polyion and the associated ion cloud, while the former do not.
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References
E. Nordmeier and W. Dauwe, Polym. J., 23, 1297 (1991).
E. Nordmeier and W. Dauwe, Polym. J., 24, 229 (1992).
E. Nordmeier, Polym. J., 25, 1 (1993).
T. Maeda and S. Fujime, Macromolecules, 17, 2381 (1984).
J. M. Schurr, J. Chem. Phys., 45, 119 (1980).
C. W. Pyun and M. J. Fixman, J. Chem. Phys., 41, 937 (1964).
S. C. Lin, W. I. Lee, and J. M. Schurr, Biopolymers, 17, 1041 (1978).
E. Nordmeier and M. D. Lechner, Polym. J., 21, 623 (1989).
R. Pecora, “Dynamic Light Scattering,” Plenum Press, New York, N.Y., 1985.
S. Fujime and T. Maeda, Macromolecules, 18, 191 (1985).
T. Maeda and S. Fujime, Macromolecules, 17, 1157 (1984).
T. Maeda and S. Fujime, Macromolecules, 18, 2430 (1985).
J. E. Hearst and W. H. Stockmayer, J. Chem. Phys., 37, 1425 (1962).
S. Fujime, M. Takasaki, and T. Maeda, Macromolecules, 20, 1292 (1987).
G. S. Manning, Q. Rev. Biophys., 11, 179 (1978).
D. Stigter, J. Colloid Interface Sci., 53, 296 (1975).
J. A. Schellman and D. Stigter, Biopolymers, 16, 1415 (1977).
M. Le Bret and B. H. Zimm, Biopolymers, 23, 287 (1984).
W. Burchard, Macromolecules, 11, 455 (1978).
W. Burchard and G. D. Patterson, “Advances in Polymer Science, 48,” Springer Press, New York, N.Y., 1983.
F. Perrin, J. Phys. Radium, 5, 497 (1934).
H. Yamakawa, “Modern Theory of Polymer Solutions,” Harper and Row, New York, N.Y., 1971.
S. Imai, J. Chem. Phys., 50, 2116 (1969).
P. Flory and W. R. Krigbaum, J. Chem. Phys., 18, 1086 (1950).
M. J. Stephen, J. Chem. Phys., 55, 3878 (1971).
J. M. Schurr, CRC Crit. Rev. Biochem., 4, 371 (1977).
P. Trivant and H. Magdelenat, Biopolymers, 22, 643 (1983).
K. Schmitz, Macromolecules, 16, 1550 (1983).
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Nordmeier, E. Studies of Polyelectrolyte Solutions IV. Effects of Ionic Strength on the Effective Polyion Charge. Polym J 25, 19–30 (1993). https://doi.org/10.1295/polymj.25.19
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DOI: https://doi.org/10.1295/polymj.25.19