The properties of dimers confined between two charged plates

Marius M. Hatlo, Klemen Bohinc, Leo Lue

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Abstract

We consider two like-charged planar surfaces immersed in solution of oppositely charged dimer counterions with a bond length l. To analyze this system, we extend and employ a self-consistent field theory that has been shown to be accurate from the weak to the intermediate through to the strong coupling regimes. In the limit of very short dimers, the results converge to the results for pointlike divalent ions. Near the surfaces, the dimers lie parallel to the charged plates. In the intermediate coupling regime, the dimers are aligned perpendicularly to the surface when they are a distance l from a surface. In the weak coupling regime, the interactions are only repulsive. At slightly higher couplings, there is a minimum in the variation of the free energy with distance at approximately the bond length of the dimers, which arises from bridging conformations of the dimers. In the intermediate coupling regime, an additional minimum in the free energy is observed at much smaller distances, which is due to the correlations between the dimers. For large dimer bond lengths, this minimum is metastable with respect to the previous minimum. However, as the bond length decreases, this minimum becomes the stable, while the minimum associated with the dimer bond length becomes metastable and eventually disappears. For shorter dimer bond length the attractive interaction is the result of correlations between counterions and charges on the surfaces. We find that dimers can mediate attractive interaction between like-charged surfaces in the intermediate coupling regime. The analysis of orientations confirms the bridging mechanism for sufficiently long dimers, whereas at high electrostatic couplings charge correlations contribute to the attraction.
Original languageEnglish
Pages (from-to)114102
Number of pages10
JournalJournal of Chemical Physics
Volume132
Issue number11
DOIs
Publication statusPublished - 21 Mar 2010

Keywords

  • bond lengths
  • electric moments
  • electric potential
  • electrostatics
  • free energy
  • molecular configurations
  • molecular moments
  • SCF calculations

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    • 23 Citations
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    Interaction between charged lipid vesicles and point- or rod-like trivalent ions

    Martin-Molina, A., Lue, L., Quesada-Perez, M. & Bohinc, K., 1 Jun 2019, In : Colloids and Surfaces B: Biointerfaces. 178, p. 525-529 5 p.

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