Silanol amphiphile

Sophisticated amphiphile designs allow us to develop bilayer-based organic-inorganic hybrids. In the example shown in Fig. 4.29, amphiphiles with alkoxysi-lane heads are used as bilayer-forming components. At the surface of the vesicle formed, cross-linked silanol groups form an inorganic silica-like structure. 

Preparation of a multilayer is possible using the self-assembled mono-layer method and appropriate molecular design (Fig. 4.37). In this method, a trichlorosilane amphiphile with a long chain terminated in a double bond was used as the monolayer component. This compound was hydrolyzed to silanol to provide a self-assembled monolayer that covalently immobihzed to... 

The growth of gold, palladium, and platinum nanoparticles in the nanostructured matrix of poly(octadecylsiloxane) (PODS) was demonstrated by Bronstein et al.102 PODS, an amphiphilic polymer with nonpolar alkyl chains and hydrophilic silanol moieties (—SiOl OH) forms a bilayer nanostructure composed of these two moieties in its hydrated form. In the presence of an aqueous solution of metal salt (e.g., Na2PdCl4, K2PtCl4, AuC13), the siloxy layer absorbed metal anions by hydrogen bonding (Scheme 5.9). After reduction, the metal ions were reduced into nanoparticles, and TEM results revealed that the nanoparticles were distributed in layer structures. The sizes of the particles were measured to be about 1-2 nm, and the narrow size distribution was attributed to the volume availability within the ordered bilayers of PODS. 

Amphiphilic Nature of Hydrolyzed TEOS. The TEOS molecules, readily solubilized in the external oil phase, interact with the water molecules present within the aggregates to produce hydrolyzed species. It is assumed that the products of hydrolysis, once formed, remain bound to the micellar aggregates (i.e., solubilized within the surfactant film or the aqueous core or both) because of their enhanced amphiphilic character (brought about by the formation of silanol groups). The exact locale for the solubilization of hydrolyzed TEOS molecules in a reverse micelle is expected to be dependent on the degree of hydrolysis for example, the most polar species [Si(OH)4] would be expected to reside within the aqueous core. Once the hydrolyzed TEOS becomes solubilized, all further reactions (further hydrolysis and condensation) are restricted to the locale of the surfactant aggregates. 

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