A silicone-based slippery polymer coating with humidity-dependent nanoscale topography

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Slippery Omniphobic Covalently Attached Liquids (SOCAL) are proposed for omnirepellent thin films.
• These films utilize self-assembled dimethylsiloxane polymer brushes grafted from silica surfaces.
• While smooth at the nanoscale, their multiscale structure and low contact angle hysteresis are key.

Purpose of the Study:

• To investigate the surface structure and properties of SOCAL coatings.
• To understand the relationship between coating process parameters and surface behavior.
• To propose a model for the chemical organization of polymers in SOCAL.

Main Methods:

• Coating deposition on glass from dimethoxydimethylsilane solution under controlled humidity.
• Ellipsometry mapping for nanometric thickness analysis.
• Contact angle hysteresis measurement using a tilting drop shape analyzer.
• Surface chemical analysis via XPS and ATR-FTIR spectroscopy.

Main Results:

• Coated surfaces revealed unexpected multiscale semispherical-like features.
• These structures did not increase contact angle hysteresis, maintaining slipperiness.
• Coating thickness and slipperiness were found to be humidity-dependent.
• A new model of polymer chemical organization was proposed to explain the behavior.

Conclusions:

• SOCAL coatings exhibit a unique multiscale surface morphology.
• This morphology, combined with specific polymer organization, results in exceptional low hysteresis.
• Humidity control during the coating process is critical for tuning surface properties and enhancing slipperiness.