Eur. Phys. J. E 5, 97-103

The osmotic coefficient of rod-like polyelectrolytes: Computer simulation, analytical theory, and experiment

M. Deserno¹, C. Holm¹, J. Blaul², M. Ballauff² and M. Rehahn<sup>3

1</sup>  Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
²  Polymer-Institut, Universität Karlsruhe, Kaiserstraße 12, 76128 Karlsruhe, Germany
³  Institut für Makromolekulare Chemie, Technische Universität Darmstadt, Petersenstraße 22, 64287 Darmstadt, Germany

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(Received 25 July 2000 and Received in final form 4 December 2000)

Abstract
The osmotic coefficient of solutions of rod-like polyelectrolytes is considered by comparing current theoretical treatments and simulations to recent experimental data. The discussion is restricted to the case of monovalent counterions and dilute, salt-free solutions. The classical Poisson-Boltzmann solution of the cell model correctly predicts a strong decrease in the osmotic coefficient, but upon closer look systematically overestimates its value. The contribution of ion-ion-correlations are quantitatively studied by MD simulations and the recently proposed DHHC theory. However, our comparison with experimental data obtained on synthetic, stiff-chain polyelectrolytes shows that correlation effects can only partly explain the discrepancy. A quantitative understanding thus requires theoretical efforts beyond the restricted primitive model of electrolytes.

PACS
61.41.+e - Polymers, elastomers, and plastics.
87.15.Aa - Theory and modeling; computer simulation.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001