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This research reports the use of organic-modified mesoporous silica particles as fillers to form organic/inorganic nanocomposites with improved thermal and mechanical properties. The particle fillers were synthesized by co-assembly of surfactant and silicate species prepared by hydrolysis and condensation reactions of tetraethoxysilane (TEOS) and (3-trimethoxysilyl)propyl methacrylate (TMSPMA) through an aerosol process. Selective surfactant removal resulted in mesoporous particles with high surface areas and with covalently bound propyl methacrylate ligands on the pore surface as indicated by XRD, TEM, N2 adsorption−desorption, FTIR, 13C NMR, 29Si NMR, and other techniques. Infiltration and subsequent in situ polymerization of (3-trimethoxysilyl)propyl methacrylate within and among the mesoporous silica particles result in nanocomposites with improved mechanical and thermal properties. Mechanical testing shows a significant increase in tensile strength, modulus, and toughness of the nanocomposites with little sacrifice on the elongation relative to the bulk poly((3-trimethoxysilyl)propyl methacrylate). DSC and SEM results indicate that chemical bonding and strong interactions between the polymer and filler, confined segmental motion of the polymer chains within the mesoporous channels, and the use of the silica particles as pseudo-cross-linking points may contribute to the improved mechanical properties.

Nanostructured materials are one of the most active areas of materials science research. This interest is due to their unique properties (e.g., magnetic, optical, electronic, mechanical) and potential applications.[1] Metallic nanostructured materials, such as metal nanowires and nanoarrays, have potential applications in nanoscale devices, sensors, nonlinear optics, magnetic storage media, and anisotropic conductors. [1,2] Synthetic methods such as electron-beam lithography, step-edge decoration, and templated growth have been developed to prepare metallic nanostructured materials.[3] The templated growth method, which involves confined growth of metallic materials to a template (e.g., a pore) followed by removal of the template, provides a flexible and affordable synthetic route to a large variety of metal nanowires. Examples of such templates include hard templates [4] (e.g., porous alumina films, track-etched polycarbonate films, and mesoporous silica) and soft templates [1a,5] (e.g., liquid-crystalline phases and amphiphilic block copolymers). The hard templating approach is conceptually simple to implement; however, the use of porous alumina or polycarbonate membranes as templates usually results in polycrystalline nanowires or nanowires with large wire diameters (20±1000 nm), which may preclude quantum confinement effects. Surfactant-templated mesoporous silica possesses unique mesoscale pore channels and a controllable pore surface chemistry, which make it an ideal template for the synthesis of metal nanowires.[6±8] Electrodeposition is an efficient and ready technique for depositing metal coatings. In this Communication, we report the fabrication of metal thin films composed of ordered arrays of metal nanowires that are grown electrochemically within silica mesoporous channels. Although syntheses of metal nanowires by chemical reduction of metallic complexes and by chemical vapor infiltration of mesoporous silica pore channels have been reported previously, [8] as-synthesized metal nanowires usually lack macroscopic continuity. In this new method, nanowires are continually grown from the bottom conductive substrate upward until the mesoporous channels are filled. This provides a ready and efficient route to macroscopic, hierarchical metal nanowire thin films. The metal nanowire thin films before and after removal of silica were characterized using X-ray diffraction (XRD). Figure 1 shows the XRD patterns of a mesoporous silica thin film (A) and a silica/metal thin film before (B) and after (C) removal of the silica template. Trace A exhibits a typical one-dimensional hexagonal pattern with an intense (100) diffraction peak with a d-spacing of 67.4 and with a (200) peak of 35.6 . The mesostructured silica after metal deposition (trace B) shows a diffraction pattern similar to that for trace A, except for the expected decrease in the XRD peak intensity at low angles.[8b] The inset shows the XRD pattern of the silica/palladium thin film at higher 2h angles. The presence of the characteristic diffraction ...

A general, aerosol-based, one-step approach was explored to synthesize microporous and mesoporous spherical carbon particles with highly porous foam-like structures from aqueous sucrose solutions containing colloidal silica particles and/or silicate cluster templates.

Ordered organic functionalized mesoporous silica containing covalently bonded diphenylphosphinoethyl ligands was synthesized using a surfactant-templating approach. Briefly, hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) and 2-(diphenylphosphino)ethyl triethoxysilane (PPETS) in an acidic condition produced phosphino-ligand containing organosilicate species. Subsequent co-assembly of the organosilicate species with surfactants led to the formation of ordered organic/inorganic nanocomposites. Selective surfactant removal by controlled thermal decomposition created organic functionalized mesoporous silica with diphenylphosphinoethyl ligands covalently bonded to the silica framework. Pore structures and pore sizes of the functionalized mesoporous silica were controlled by using different surfactants such as P123, F127, Brij-58, and CTAB. It was found that the added organosilane may significantly affect the mesostructure possibly through participating in the cooperative assembly process. These organic functionalized mesoporous silicas were bonded with palladium ions, resulting in the formation of catalytically active organometallic complexes that show excellent activities in both Heck and epoxides allylation reactions. Compared with the conventional homogeneous catalysts, these heterogeneous organometallic complexes can be readily separated from the reaction systems and reused without deteriorating their catalytic activities. This study provides a direct synthesis approach to efficiently synthesize a large variety of organic functionalized mesoporous silica with controlled pore sizes, pore surface chemistry, and pore structure for heterogeneous catalysts and other applications.

An efficient, productive, and low-cost aerosol-assisted self-assembly process has been developed to produce organically modified mesoporous silica particles via a direct co-condensation of silicate species and organosilicates that contain nonhydrolyzable functional groups in the presence of templating surfactant molecules. Different surfactants including cetyltrimethylammonium bromide, nonionic surfactant Brij-56, and triblock copolymer P123 have been used as the structure-directing agents. The organosilanes used in this study include tridecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane, methytriethoxysilane, vinyltrimethoxysilane, and 3-(trimethoxysilyl)propyl methacrylate. X-ray diffraction and transmission electron microscopy studies indicate the formation of particles with various mesostructures. Fourier transform infrared and solid-state nuclear magnetic resonance spectra confirm the organic ligands are covalently bound to the surface of the silica framework. The porosity, pore size, and surface area of the particles were characterized using nitrogen adsorption and desorption measurements. This method provides a direct synthesis route to efficiently synthesize a large variety of organic functionalized mesoporous silica particles with controlled pore sizes, pore surface chemistry, and pore structures for catalyst, filler, and other applications.

Spherical mesoporous silica particles with entrapped metal nanoparticles are synthesized from a onestep aerosol-assisted self-assembly process using sols of an alkoxysilane, ethanol, surfactant, water, HCl, and metal precursors (e.g., salts or complexes). Utilizing nitrogen as a carrier gas, the sol is sent through an atomizer, producing aerosol droplets, which are passed through a tubular furnace heated to 400 °C. Solvent evaporation from the droplets enriches the nonvolatile components and results in the coassembly of silicate and surfactant into 3-dimensional mesostructures with incorporated metal precursors. Lamellar, cubic, and hexagonal mesostructures are achieved by using different surfactants. Subsequent calcination of the surfactant and reduction of the metal result in spherical mesostructured porous silica particles with supported metal nanoparticles. Nitrogen sorption techniques, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction are used to characterize the particles. Mesoporous silica particles with 0.5% Pd are tested as a catalyst in the hydrodechlorination reaction of 1,2-dichloroethane and exhibit ∼100% conversion above 350 °C and ∼100% ethylene selectivity, demonstrating the potential of such nanocomposites as catalysts.

The hydrogen adsorption of mesoporous carbon materials with different mesostructures, surface areas, and pore volumes has been investigated. Experimental results indicate that the hydrogen adsorption capacities are dominantly related to their surface areas. A hydrogen adsorption capacity of 1.78 wt % was obtained at 77 K and ambient pressure of 850 mm Hg (0.11 MPa) for the mesoporous carbon with a surface area of 2314m2∕g.