Comparative Molecular Dynamics Simulation of Wetting on Liquid-like Surfaces.

Area of Science:

• Surface Science
• Materials Science
• Computational Chemistry

Background:

• Understanding liquid-like surfaces (LLS) is crucial for designing advanced materials.
• Flexible polymer brushes like polydimethylsiloxane (PDMS) and perfluoropolyether (PFPE) are candidates for LLS.
• Rigid molecules such as trichloro(octadecyl) silane (OTS) and trichloro(1H,1H,2H,2H-perfluorooctyl) silane (PFOS) serve as comparisons.

Purpose of the Study:

• To investigate droplet wetting and motion on LLS with varying grafting conditions using molecular dynamics simulations.
• To compare the behavior of flexible polymer brushes (PDMS, PFPE) against rigid molecules (OTS, PFOS).
• To identify optimal grafting densities for LLS construction.

Main Methods:

• Molecular dynamics simulations were employed.
• Droplet wetting and motion dynamics were analyzed.
• Grafting conditions, including density and molecular weight, were varied.

Main Results:

• Droplets formed indentations and wetting ridges on PDMS and PFPE surfaces, confirming their liquid-like nature.
• Grafting density of mobile chains significantly influenced wetting properties more than molecular weight.
• A parameter map was developed to guide LLS design based on grafting density and molecular weight.
• Droplets predominantly rolled on LLS, with motion patterns changing only at low grafting densities and hydrophilic conditions.

Conclusions:

• Flexible polymer brushes demonstrate liquid-like surface properties.
• Grafting density is a critical parameter for optimizing LLS performance.
• The developed model provides guidelines for the rational design of LLS for specific applications.