Rediscovering Silicones: “Unreactive” Silicones React with Inorganic Surfaces

Abstract

Chemical reactions of linear trimethylsilyl-terminated poly(dimethylsiloxane)s with the surfaces of oxidized silicon, titanium, aluminum, and nickel are reported. These reactions lead to covalently attached poly(dimethylsiloxane) polymer chains and to hydrophobized inorganic surfaces. Linear silicones of this type (silicone oils) are generally not considered to be reactive with inorganic oxide surfaces, and an enormous research effort over the last 50 years to develop other silicon-containing reagents with reactive functional groups did not consider the simple alternative that we report. In retrospect, with the acknowledgment of the facile equilibration of siloxane chains with either acid or base catalysis (that was well-known in the 1940s and 1950s), the synthetic approach to functionalized inorganic surfaces by use of linear silicones is obvious. We also report the reactions of poly[3,3,3-trifluoropropyl)methylsiloxane], poly[(3-aminopropyl)methylsiloxane-co-dimethylsiloxane], poly(phenylmethylsiloxane-co-dimethylsiloxane), and poly(dimethylsiloxane-block-ethylene oxide) with oxidized silicon surfaces, which suggest that this reaction is general for silicones.