Density Functional Theory for Polyelectrolytes near Oppositely Charged Surfaces

We report a nonlocal density functional theory of polyelectrolyte solutions that faithfully accounts for both short- and long-range correlations neglected in a typical mean-field method. It is shown that for systems with strong electrostatic interactions, the long-range correlations are subdued by direct Coulomb attractions, thereby manifesting strong local excluded-volume effects. The theory has also been used to describe the influence of the polyion chain length and small ion valence on charge inversion due to the adsorption of polyelectrolytes at an oppositely charged surface.

Figure 1

Distributions of (a) polyion segments and (b) cations near a charged surface. Solid lines are predictions of the NLDFT, and symbols are simulation data [22, 38].

Figure 2

Predictions of the NLDFT for (a) distributions of polyion segments and cations and (b) mean electrostatic potentials and integrated charge distributions near an oppositely charged surface.

Figure 3

The minimal integrated charge versus the polyion chain length predicted by the NLDFT.