Monolayers of hard rods on planar substrates. II. Growth

Area of Science:

• Physics
• Materials Science
• Chemical Engineering

Background:

• Understanding the self-assembly of anisotropic particles is crucial for designing advanced materials.
• Hard-rod systems, like spherocylinders, exhibit rich phase behavior driven by excluded volume interactions.
• Monolayer growth dynamics influence the properties of thin films and interfaces.

Purpose of the Study:

• To investigate the growth dynamics of hard-rod monolayers using both lattice and continuum models.
• To analyze the factors governing the evolution of nematic order during deposition.
• To explore the impact of non-equilibrium effects and substrate interactions on growth morphology.

Main Methods:

• Kinetic Monte Carlo simulations for the lattice model with discrete orientations.
• Dynamic density functional theory for the lattice model.
• Dynamic Monte Carlo simulations for the continuum model of hard spherocylinders.
• Analysis of particle orientation, diffusion, and relaxation dynamics.

Main Results:

• Nematic order, characterized by an excess of upright particles, emerges as an entropic effect, leading to a continuous transition.
• Significant non-equilibrium effects are observed with attractive substrate potentials that favor lying rods.
• Qualitative agreement between lattice and continuum models is achieved when characteristic timescales for diffusion, relaxation, and deposition are appropriately matched.
• The study discusses the extension of monolayer findings to multilayer growth scenarios.

Conclusions:

• The growth of hard-rod monolayers is primarily governed by equilibrium thermodynamics, with nematic ordering driven by entropy.
• Non-equilibrium dynamics become significant under specific substrate conditions, influencing the final film structure.
• The chosen models provide a robust framework for studying anisotropic particle assembly, with implications for thin-film deposition and self-assembly processes.