Self-diffusion in submonolayer colloidal fluids near a wall

Anekal, Samartha G.; Bevan, Michael A.

doi:doi:10.1063/1.2211616

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Polymer brushes in cylindrical pores: Simulation versus scaling theory

The structure of flexible polymers endgrafted in cylindrical pores of diameter D is studied as a function of chain length N and grafting density σ, assuming good solvent conditions. A phenomenological scaling theory, describing the variation of the linear dimensions of the chains with σ, is developed and tested by molecular dynamics simulations of a bead-spring model. Different regimes are identified, depending on the ratio of D to the size of a free polymer N3/5. For D>N3/5 a crossover occu...

Comment on “Global thermodynamics of hydrophobic cavitation, dewetting, and hydration” [ J. Chem. Phys. 123, 184504 (2005) ]

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Theoretical expressions are developed to describe self-diffusion in submonolayer colloidal fluids that require only equilibrium structural information as input. Submonolayer colloidal fluids are defined for the purpose of this work to occur when gravity confines colloids near a planar wall surface so that they behave thermodynamically as two dimensional fluids. Expressions for self-diffusion are generalized to consider different colloid and surface interaction potentials and interfacial concentrations from infinite dilution to near fluid-solid coexistence. The accuracy of these expressions is demonstrated by comparing self-diffusion coefficients predicted from Monte Carlo simulated equilibrium particle configurations with standard measures of self-diffusion evaluated from Stokesian Dynamics simulated particle trajectories. It is shown that diffusivities predicted for simulated equilibrium fluid structures via multibody hydrodynamic resistance tensors and particle distribution functions display excellent agreement with values computed from mean squared displacements and autocorrelation functions of simulated tracer particles. Results are obtained for short and long time self-diffusion both parallel and normal to underlying planar wall surfaces in fluids composed of particles having either repulsive electrostatic or attractive van der Waals interactions. The demonstrated accuracy of these expressions for self-diffusion should allow their direct application to experiments involving submonolayer colloidal fluids having a range of interaction potentials and interfacial concentrations.

Article Outline

INTRODUCTION
THEORY
1. Equation of motion in submonolayer colloidal fluids
2. Dissipative, multibody hydrodynamic forces
3. Conservative colloidal, surface, and gravitational forces
4. Self-diffusion in submonolayer colloidal fluids
5. Mean squared displacements and autocorrelation functions
RESULTS AND DISCUSSION
1. Repulsive and attractive equilibrium submonolayer colloidal fluids
2. Diffusion parallel to the underlying planar surface
3. Diffusion normal to the underlying planar surface
SUMMARY AND CONCLUSIONS

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KEYWORDS and PACS

Keywords

colloids, self-diffusion, Monte Carlo methods, surface potential

PACS

82.70.Dd

Colloids
66.10.C-

Diffusion and thermal diffusion

ARTICLE DATA

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http://link.aip.org/link/doi/10.1063/1.2211616

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0021-9606 (print)

1089-7690 (online)

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American Institute of Physics

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