Effective interactions between oppositely charged polyelectrolytes in the presence of salt

Abstract

We generalize the familiar effective DLVO (Derjaguin–Landau–Verwey–Overbeek) pair potential between charged, hard core colloidal particles to the case of solutions of oppositely charged, penetrable polyelectrolyte coils in the presence of microions, within the framework of classical Density Functional Theory. The limiting behaviour of the effective potentials is derived in the limits of weak and strong microion screening; in the latter regime the effective potentials are shown to go over to a universal Gaussian form, multiplied by the square of the microion Debye screening length. The physical implications of screening on polyelectrolyte aggregation are discussed and illustrated by preliminary Monte Carlo simulations and the results of fluid integral equations for the polyelectrolyte pair structure.

Keywords:

• polyelectrolytes
• colloids
• Monte Carlo simulations
• liquid structure
• density functional theory

Acknowledgements

JPH would like to express his sincere gratitude to Luciano Reatto for fruitful interactions over many years and for his gracious hospitality in Milan, as well as for guiding him to Bernardino Luini's remarkable frescoes at San Maurizio Church. This work was funded by the Austrian Science Foundation (FWF) under Project No. P19890-N16.

Notes

Note

1. NVT MC simulations were performed for a system of N = 1000 polyions in a cubic cell with periodic boundary conditions. In view of the softness of the potential, attempted displacements were generated over a cube of side L, where L is the side of the simulation cell. For computational efficiency, the potential (34) was truncated at , 7.0, and 10.0 for , 1.0, and 0.5, respectively.