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Photo Jan Forsman

Jan Forsman

Professor

Photo Jan Forsman

Simulations of surface forces in polyelectrolyte solutions.

Author

  • Martin Turesson
  • Clifford E Woodward
  • Torbjörn Åkesson
  • Jan Forsman

Summary, in English

We have simulated interactions between charged surfaces in the presence of oppositely charged polyelectrolytes by coupling perturbations in the isotension ensemble to a free energy variance minimization scheme. For polymeric systems, this method completely outperforms configurationally biased versions of grand canonical simulations. Proper diffusive equilibrium between bulk and slit has been established for polyelectrolytes with up to 60 monomers per chain. A consequence of imposing diffusive equilibrium conditions, in contrast to previous more restricted models, is the possibility of surface charge inversion; ion-ion correlation and the cooperativity of monomer adsorption drive the formation of a polyion layer close to the surface, that overcompensates the nominal surface charge. This is observed even at modest surface charge densities, and leads to a build up of a long ranged electrostatic barrier. In addition, the onset of charge inversion requires very low bulk polymer densities. Due to screening effects, this leads to a higher and more long-ranged free energy barrier at low, compared to high, bulk densities. Oscillatory forces, reminiscent of those found in simple hard sphere systems, are resolved in the high concentration regime. As a consequence of a second surface charge inversion, the system "stratifies" to form a stable polyelectrolyte layer in the central part of the slit, stabilized by the adsorbed surface layers.

Department/s

  • Computational Chemistry

Publishing year

2008

Language

English

Pages

5116-5125

Publication/Series

The Journal of Physical Chemistry Part B

Volume

112

Issue

16

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Theoretical Chemistry (including Computational Chemistry)

Status

Published

ISBN/ISSN/Other

  • ISSN: 1520-5207