Rediscovering silicones: "unreactive" silicones react with inorganic surfaces

Area of Science:

• Materials Science
• Surface Chemistry
• Polymer Chemistry

Background:

• Linear silicones, specifically trimethylsilyl-terminated poly(dimethylsiloxane)s, were not traditionally considered reactive with inorganic oxide surfaces.
• Extensive research has focused on developing specialized silicon-containing reagents for surface functionalization, overlooking simpler alternatives.

Purpose of the Study:

• To investigate the chemical reactivity of linear silicones with various oxidized inorganic surfaces.
• To demonstrate a novel method for covalently attaching polymer chains and hydrophobizing surfaces using readily available silicones.

Main Methods:

• Reacting linear trimethylsilyl-terminated poly(dimethylsiloxane)s with oxidized silicon, titanium, aluminum, and nickel surfaces.
• Examining the reactions of other functionalized silicones, including poly[3,3,3-trifluoropropyl)methylsiloxane] and poly(dimethylsiloxane)-block-ethylene oxide), with oxidized silicon.

Main Results:

• Covalent attachment of poly(dimethylsiloxane) chains to inorganic surfaces was achieved.
• The treated surfaces exhibited hydrophobized properties.
• The reaction was found to be general for various types of silicones, including functionalized variants.

Conclusions:

• Linear silicones can readily react with oxidized inorganic surfaces, providing a straightforward route to surface modification.
• This facile reaction, enabled by siloxane chain equilibration under acid or base catalysis, represents a significant, yet previously overlooked, synthetic approach.
• The findings suggest broad applicability for functionalizing diverse inorganic materials with silicones.