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Spinodal fractionation in a polydisperse square-well fluid
1Soft Matter Group, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, England, United Kingdom.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 26, 2012
Summary
Particle size differences in colloidal dispersions drive fractionation during phase separation. This size demixing can be unexpectedly reversed by altering interparticle potentials, offering insights into real-world colloidal systems.
Area of Science:
- Colloid and Interface Science
- Soft Matter Physics
- Computational Chemistry
Background:
- Colloidal dispersions are ubiquitous in materials science and biology.
- Understanding phase separation dynamics, like spinodal decomposition, is crucial for controlling material properties.
- The impact of particle size polydispersity on these processes is not fully understood.
Purpose of the Study:
- To model gas-liquid spinodal decomposition in a size-polydisperse colloidal system.
- To investigate the phenomenon of particle size fractionation between coexisting phases.
- To explore the influence of interparticle potentials on size fractionation direction.
Main Methods:
- Kinetic Monte Carlo (KMC) simulations were employed.
- A size-polydisperse square well fluid model was used to represent colloidal dispersions.
- Perturbative equilibrium theory was utilized to rationalize simulation observations.
Main Results:
- Particle size fractionation (demixing) was observed shortly after the onset of phase ordering.
- The direction of size fractionation was found to be reversible by changing interparticle potentials.
- Simulation results provide quantitative insights into fractionation effects in colloidal systems.
Conclusions:
- Kinetic Monte Carlo simulations are valuable tools for studying polydisperse colloidal systems.
- Particle size polydispersity significantly influences phase separation behavior.
- The choice of interparticle potential can critically affect size fractionation, even in near-monodisperse systems.
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