Molecular dynamics simulations of surfactant self-organization at a solid-liquid interface

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Surfactant self-assembly is crucial for various applications.
• Understanding molecular behavior at surfaces informs material design.
• Graphite surfaces present unique interaction potentials for adsorbed molecules.

Purpose of the Study:

• To investigate the self-organization of nonionic surfactants on graphite-like surfaces.
• To determine the influence of alkyl chain length on surfactant aggregation morphology.
• To compare simulation results with experimental atomic force microscopy (AFM) data.

Main Methods:

• Coarse-grain molecular dynamics simulations were employed.
• Nonionic surfactants (n-alkyl poly(ethylene oxide)) and water were modeled using coarse-grain potentials.
• An implicit model represented the planar graphite surface.

Main Results:

• Surfactant aggregation morphology is dependent on alkyl chain length.
• Short-chain surfactants form a monolayer with thickness matching the alkane tail.
• Longer-chain surfactants aggregate into continuous hemicylinders with a diameter of approximately 5.0 +/- 0.5 nm.

Conclusions:

• Alkyl chain length is a key factor governing surfactant self-organization on graphite.
• Simulation results for hemicylinder formation agree well with experimental AFM observations.
• This study provides insights into surfactant-surface interactions and morphology control.