A molecular simulation study of an organosilane self-assembled monolayer/SiO2 substrate interface.

Area of Science:

• Surface Science
• Materials Chemistry
• Computational Chemistry

Background:

• Alkylsilane self-assembled monolayers (SAMs) on SiO(2) are crucial for surface modification.
• Understanding the interfacial bonding network is key to controlling SAM properties.

Purpose of the Study:

• To investigate the bonding network of alkylsilane SAMs on SiO(2) substrates.
• To determine the relationship between interfacial bond density and molecular ordering.
• To explain experimental variations in SAM preparation.

Main Methods:

• Canonical Monte Carlo (MC) simulations were employed.
• Metropolis MC method sampled different interfacial bonding topologies.
• AMBER potential with new organosilicon parameters optimized structures.

Main Results:

• The SAM-SiO(2) interface features a polysiloxane network with anchoring and cross-linking Si-O-Si bonds.
• Increased Si-O-Si bond density decreases the ratio of anchoring to cross-linking bonds.
• Higher Si-O-Si bond density leads to disordered molecular packing.

Conclusions:

• The density of Si-O-Si bonds significantly impacts the lateral ordering of alkylsilane molecules.
• Variations in experimental SAM preparation may stem from differing interfacial Si-O-Si bond densities.
• This study provides insights into controlling SAM structure and properties.