Self-assembled surfactants on patterned surfaces: confinement and cooperative effects on aggregate morphology

Area of Science:

• Surface Science and Nanotechnology
• Computational Chemistry and Materials Science

Background:

• Surfactant adsorption and self-assembly are crucial for manufacturing nanostructured materials.
• Limited quantitative data exists on surfactant behavior on chemically heterogeneous surfaces.
• Understanding these interactions is key for designing advanced materials and coatings.

Purpose of the Study:

• To investigate surfactant adsorption and self-assembly on patterned flat surfaces with chemical heterogeneity.
• To quantify the effects of lateral confinement on surfactant aggregate morphology.
• To explore cooperative effects in surfactant assembly on surfaces with multiple adsorbing stripes.

Main Methods:

• Utilized equilibrium dissipative particle dynamics (DPD) simulations.
• Modeled adsorption of surfactants onto flat surfaces patterned with one or two stripes.
• Simulated interactions on stripes surrounded by a surfactant-repelling surface to control confinement.

Main Results:

• On wide stripes (homogeneous conditions), surfactants formed flat monolayers.
• Decreasing stripe width led to transitions from monolayers to hemi-cylinders, hemi-spheres, and individual surfactants.
• Cooperative effects were observed between closely spaced stripes (< one surfactant length), forming hemi-cylindrical shells and irregular structures.

Conclusions:

• Lateral confinement significantly alters surfactant aggregate morphology on patterned surfaces.
• The width and spacing of adsorbing stripes dictate the self-assembly outcome.
• Findings provide valuable insights for designing novel nanostructured materials and coatings for diverse applications.