Properties of patchy colloidal particles close to a surface: a Monte Carlo and density functional study

Area of Science:

• Soft matter physics
• Computational chemistry
• Statistical mechanics

Background:

• Understanding fluid behavior near interfaces is crucial for materials science and colloid chemistry.
• Patchy particle models offer a simplified yet powerful approach to studying complex fluids with directional interactions.
• Density functional theory (DFT) is a key theoretical tool for predicting properties of inhomogeneous fluids.

Purpose of the Study:

• To investigate the interfacial behavior of a patchy particle model near a hard wall.
• To compare the predictive capabilities of two distinct density functional theory (DFT) approaches with Monte Carlo simulations.
• To analyze the influence of temperature and bulk fluid properties on surface phenomena.

Main Methods:

• Monte Carlo (MC) simulations were employed to model the system.
• Two variants of Wertheim's first-order perturbation theory within DFT were utilized.
• The study analyzed equilibrium bulk phase diagrams and surface density profiles.

Main Results:

• The density profile near the wall exhibits a crossover from adsorption to desorption with decreasing temperature for a specific isochore.
• Both DFT approaches provide reasonable accuracy in describing the bulk network liquid and its interfacial behavior.
• At very low temperatures, DFT fails to capture a second adsorption regime due to the neglect of orientational correlations, which simulations reveal.

Conclusions:

• The study highlights the successes and limitations of DFT in modeling complex interfacial phenomena in patchy particle systems.
• Surface-induced orientational order plays a significant role at low temperatures, necessitating advanced theoretical treatments.
• The findings provide insights into the design and behavior of functional materials based on self-assembling particles.