Freezing in flat monolayers of soft spherocylinders

Area of Science:

• Soft Matter Physics
• Materials Science
• Liquid Crystals

Background:

• Lamellar and smectic phases possess complex intralamellar structures that are poorly understood at the microscopic level.
• Understanding phase transitions in confined systems is crucial for designing novel materials and devices.

Purpose of the Study:

• To investigate the impact of volume exclusion on the phase transitions of a flat membrane composed of soft repulsive spherocylinders.
• To determine the critical packing fraction for disorder-order transitions and explore the role of orientational entropy.

Main Methods:

• Molecular dynamics simulations were employed to model the behavior of soft repulsive spherocylinders in a 2D membrane.
• Analysis of phase transitions, including the identification of liquid crystal and crystal phases.
• Comparison with theoretical models, specifically a density functional theory for 2D rod fluids.

Main Results:

• A universal packing fraction (η ≈ 0.81) was identified for the disorder-order phase transition, independent of spherocylinder aspect ratio.
• A 2D hexatic phase region was observed near the phase transition.
• The transition packing fraction is significantly higher than that of hard disk fluids, attributed to residual orientational entropy.

Conclusions:

• The study provides insights into liquid crystal phase stability under strong planar confinement.
• Findings contribute to the understanding of intralamellar structures and phase behavior in 2D systems.
• Results align with and extend recent experimental studies on nanorods on 2D substrates.