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6603772 
Journal Article 
COLLOIDAL SILICA-BEARING HYDROSILANE GROUPS 
Ketelson, HA; Brook, MA; Pelton, RH; , 
1995 
Yes 
Chemistry of Materials
ISSN: 0897-4756
EISSN: 1520-5002 
AMER CHEMICAL SOC 
WASHINGTON 
7 
7 
1376-1383 
English 
WOS:A1995RK99300016 
Stober silica was functionalized with three silyl coupling agents: triethoxysilane (TES), dimethylethoxysilane (DMES, and vinyltrimethoxysilane (VM). Microelectrophoresis, dynamic light scattering, and elemental analysis were used to study the degree of interaction between the silyl coupling agents and the silica surface. Small changes in the electrophoretic mobilities and particle diameters between the unmodified (Si-OH) and DMES silica (Si-DMES) showed that Si-DMES coupled to the surface through a single point of attachment. In contrast, the surface coupling reaction with TES (Si-TES) led to multilayered, oligomeric species bound to the surface. The electrophoretic mobilities in acetone decreased from -4.47 x 10(-8) m(2) V-1 s(-1) for Si-OH to -3.87 x 10(-8) m(2) V-1 s(-1) for Si-TES and the particle diameter of Si-TES was 13 nn larger than the bare silica. Although VTM has three alkoxy groups capable of forming large cross-linked oligomeric species, the mobility of the VTM-modified silica (Si-VTM) decreased to only -4.41 x 10(-8) m(2) V-(l) and the particle diameter increased by only 4 nm. The surface reaction with VTM showed that the nature of the functional group on the silyl coupling agent played an important role in determining the reactivity of alkoxy groups with the silica surface. Using the Pt-catalyzed hydrosilation reaction, Si-TES was reacted with vinylnaphthalene (Si-TES-VN), styrene (Si-TES-ST), and vinyl-terminated poly(dimethylsiloxanes) (Si-TES-PDMS). These reactions demonstrated that Stober silica modified with TES can lead to a variety of colloidally stable model dispersions in solvents varying in polarity from water to hexane. The modified silica systems were characterized by C-13 and Si-29 solid-state NMR, diffuse reflectance infrared spectroscopy (DRIFTS), elemental analysis, transmission electron microscopy, fluorescence and UV-vis absorption spectroscopy.