The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here: https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

Default user image.

Bo Söderberg

Teaching staff

Default user image.

The electrostatic persistence length calculated from Monte Carlo, variational and perturbation methods

Author

  • Magnus Ullner
  • Bo Jönsson
  • Carsten Peterson
  • Ola Sommelius
  • Bo Söderberg

Summary, in English

Monte Carlo simulations and variational calculations using a Gaussian ansatz are applied to a model consisting of a flexible linear polyelectrolyte chain as well as to an intrinsically stiff chain with up to 1000 charged monomers. Addition of salt is treated implicitly through a screened Coulomb potential for the electrostatic interactions. For the flexible model the electrostatic persistence length shows roughly three regimes in its dependence on the Debye-Hückel screening length, κ-1. As long as the salt content is low and κ-1 is longer than the end-to-end distance, the electrostatic persistence length varies only slowly with κ-1. Decreasing the screening length, a controversial region is entered. We find that the electrostatic persistence length scales as √ξp/κ, in agreement with experiment on flexible polyelectrolytes, where ξp is a strength parameter measuring the electrostatic interactions within the polyelectrolyte. For screening lengths much shorter than the bond length, the κ-1 dependence becomes quadratic in the variational calculation. The simulations suffer from numerical problems in this regime, but seem to give a relationship half-way between linear and quadratic. A low temperature expansion only reproduces the first regime and a high temperature expansion, which treats the electrostatic interactions as a perturbation to a Gaussian chain, gives a quadratic dependence on the Debye length. For a sufficiently stiff chain, the persistence length varies quadratically with κ-1 in agreement with earlier theories.

Department/s

  • Biophysical Chemistry
  • Computational Biology and Biological Physics - Has been reorganised

Publishing year

1997-07-22

Language

English

Pages

1279-1287

Publication/Series

Journal of Chemical Physics

Volume

107

Issue

4

Document type

Journal article

Publisher

American Institute of Physics (AIP)

Status

Published

ISBN/ISSN/Other

  • ISSN: 0021-9606