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Competing interactions in two dimensional Coulomb systems: surface charge heterogeneities in coassembled
Sharon M Loverde1, Yury S Velichko, Monica Olvera de la Cruz
1Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, USA.
The Journal of Chemical Physics
|April 22, 2006
Summary
Oppositely charged lipid bilayers can segregate locally. The balance between short-range attraction and long-range electrostatic forces dictates the scale of this microphase segregation.
Area of Science:
- Soft Matter Physics
- Computational Chemistry
- Materials Science
Background:
- Binary mixtures of oppositely charged components, like cationic and anionic lipid bilayers, can exhibit local segregation on a plane.
- The interplay between short-range attractive interactions favoring macroscopic segregation and long-range electrostatic interactions favoring mixing determines the microphase segregation length scale.
Purpose of the Study:
- To investigate the microphase segregation behavior of binary mixtures of oppositely charged components confined to a 2D plane.
- To explore the influence of interaction strengths and salt concentration on domain formation and ordering.
Main Methods:
- Analytical examination of the system's free energy in high-temperature (small fluctuations) and low-temperature (periodic ordering) regimes.
- Molecular dynamics simulations of oppositely charged monomers with Lennard-Jones potentials in a 2D plane.
- Varying the strengths of short-range and long-range interactions, and introducing salt to the system.
Main Results:
- The system forms well-defined domains with characteristic periodic length scales and orientational ordering of interfaces.
- Analytical predictions for free energy were examined in different temperature regimes.
- Addition of salt disrupts domain ordering, leading to macroscopic phase segregation, consistent with analytical models.
Conclusions:
- The microphase segregation in 2D charged lipid mixtures is governed by the competition between short-range and long-range interactions.
- Molecular dynamics simulations successfully replicate and validate analytical predictions regarding domain formation and salt-induced macroscopic segregation.
- The study provides insights into controlling self-assembly and phase behavior in confined charged systems.
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