Simulations of Surface Forces in Polyelectrolyte Solutions
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- 作者：Martin Turesson ; Clifford E. Woodward ; Torbjö ; rn Å ; kesson ; Jan Forsman
- 刊名：Journal of Physical Chemistry B
- 出版年：2008
- 出版时间：April 24, 2008
- 年：2008
- 卷：112
- 期：16
- 页码：5116 - 5125
- 全文大小：474K
- 年卷期：v.112,no.16(April 24, 2008)
- ISSN：1520-5207
文摘
We have simulated interactions between charged surfaces in the presence of oppositely charged polyelectrolytesby coupling perturbations in the isotension ensemble to a free energy variance minimization scheme. Forpolymeric systems, this method completely outperforms configurationally biased versions of grand canonicalsimulations. Proper diffusive equilibrium between bulk and slit has been established for polyelectrolytes withup to 60 monomers per chain. A consequence of imposing diffusive equilibrium conditions, in contrast toprevious more restricted models, is the possibility of surface charge inversion; ion-ion correlation and thecooperativity of monomer adsorption drive the formation of a polyion layer close to the surface, thatovercompensates the nominal surface charge. This is observed even at modest surface charge densities, andleads to a build up of a long ranged electrostatic barrier. In addition, the onset of charge inversion requiresvery low bulk polymer densities. Due to screening effects, this leads to a higher and more long-ranged freeenergy barrier at low, compared to high, bulk densities. Oscillatory forces, reminiscent of those found insimple hard sphere systems, are resolved in the high concentration regime. As a consequence of a secondsurface charge inversion, the system "stratifies" to form a stable polyelectrolyte layer in the central part ofthe slit, stabilized by the adsorbed surface layers.