Polymer brushes in solvents of variable quality: molecular dynamics simulations using explicit solvent

Area of Science:

• Polymer Physics
• Soft Matter Physics
• Computational Chemistry

Background:

• Understanding polymer brushes is crucial for surface science and materials engineering.
• The behavior of polymer chains grafted to a substrate is influenced by solvent quality and grafting density.
• Previous studies often used implicit solvent models, limiting detailed structural and thermodynamic insights.

Purpose of the Study:

• To investigate the structure and thermodynamic properties of end-grafted flexible polymer chains.
• To analyze the impact of grafting density and solvent quality on polymer brush behavior.
• To provide a molecular-level understanding of polymer brush-solvent interactions and surface properties.

Main Methods:

• Molecular dynamics simulations using a coarse-grained bead-spring model for polymers.
• Pointlike particles represent solvent molecules with Lennard-Jones interactions.
• Analysis of density profiles, structural properties (gyration radius, bond orientational parameters), and lateral pressure.

Main Results:

• Obtained density profiles of solvent and monomers, revealing structural changes with grafting density.
• Quantified the reduction in surface tension as a function of grafting density.
• Characterized chain stretching forces, mobility profiles, and relaxation times.
• Observed qualitative agreement between simulated brush height/interfacial width and experimental data.

Conclusions:

• Grafting density and solvent quality significantly influence polymer brush structure and thermodynamics.
• Molecular dynamics simulations provide valuable insights into polymer brush behavior, complementing experimental observations.
• The study offers a detailed understanding of surface tension reduction and interfacial properties in polymer brush systems.