Morphology-controlled synthesis of poly(oxyethylene)silicone or alkylsilicone surfactants with explicit, atomically defined, branched, hydrophobic tails.

Silicone surfactants are widely used in commerce because of the unusual surface activity when compared with fluorocarbon or hydrocarbon surfactants. However, most silicone surfactants are comprised of ill-defined mixtures, which preclude the development of an understanding of structure-surface activity relationships. Herein, we report a synthetic strategy that permits exquisite control over silicone structure by using the B(C(6)F(5))(3)-catalyzed condensation of hydro- and alkoxysilanes. Six different, precise hydrophobes were then mated to hydrophilic poly(oxyethylene)s of three different molecular weights by a metal-free click cyclization to generate a library of explicit silicone surfactants. These compounds were calculated to have a relatively linear value range of the hydrophilic-lipophilic balance, ranging from about 8 to about 15. The solubility of some of the compounds was too low to measure a critical micelle concentration (CMC). The others exhibited a broad range of surface tension values at the CMC that depend both on the length of the hydrophilic tail and, more importantly, the nature of the hydrophobic head group. Subtle distinctions in surfactant-related properties, which can be attributed to the three-dimensional structures, can be seen for compounds with comparable numbers of hydrocarbons and silicon groups.

Amphiphilic silicone architectures via anaerobic thiol-ene chemistry.

Despite broad application, few silicone-based surfactants of known structure or, therefore, surfactancy have been prepared because of an absence of selective routes and instability of silicones to acid and base. Herein the synthesis of a library of explicit silicone-poly(ethylene glycol) (PEG) materials is reported. Pure silicone fragments were generated by the B(C(6)F(5))(3)-catalyzed condensation of alkoxysilanes and vinyl-functionalized hydrosilanes. The resulting pure products were coupled to thiol-terminated PEG materials using photogenerated radicals under anaerobic conditions.

Siloxane-triarylamine hybrids: discrete room temperature liquid triarylamines via the Piers-Rubinsztajn reaction.

A series of room temperature liquid siloxane-triarylamine hybrids were synthesized using the Piers-Rubinsztajn reaction. These materials displayed well behaved electrochemical oxidation and low T(g)'s and were free-flowing liquids. The interaction between the Lewis acidic tris(pentafluorophenyl)borane catalyst and the Lewis basic starting triarylamine substrate was also investigated by steady state UV-vis spectroscopy and (19)F NMR.

Rapid assembly of explicit, functional silicones.

The impressive surface activity of silicones can be enhanced by the incorporation of hydrophilic organic functional groups and polymers. Traditional routes to such compounds, which typically involve platinum-catalyzed hydrosilylation, suffer from incompatibility with certain functional groups. B(C(6)F(5))(3)-catalyzed condensation of hydrosilanes with alkoxysilanes offers new opportunities to prepare explicit silicone structures. We demonstrate here that conversion of alcohols to silyl ethers competes unproductively with alkoxysilane conversion to disiloxanes. By contrast, a wide range of structurally complex alkyl halide and oligovinyl compounds can be readily made in high yield. Thermal 3+2-cycloadditions and thiol-ene click reactions are used to convert these compounds into surface active materials.

Testing the functional tolerance of the Piers-Rubinsztajn reaction: a new strategy for functional silicones.

The Piers-Rubinsztajn reaction, involving B(C(6)F(5))(3)-catalyzed siloxane formation from hydrosilanes + alkoxysilanes, is tolerant of a wide variety of functional groups, and provides a generic strategy for the preparation of structurally complex functional silicones.