Well-defined rodlike and fiberlike SBA-15 mesoporous silicas have been selectively synthesized from an aqueous reaction mixture consisting of a commercial sodium silicate solution, P123 triblock copolymer and HCl. The morphologies and physicochemical properties of the products were found to be greatly affected by the shearing stress exerted by cylindrical silicated-surfactant micelles in a flowing solution, referred to hereafter as "shearing flow". Monodispersed rodlike particles ca. 0.5-µm wide and ca. 1-2-µm long were formed under static reaction conditions, whereas continuous stirring of the reaction mixture led to the formation of fiberlike silicas with lengths of several hundred micrometers and a relatively uniform width of ca. 10 µm. The effects of the synthesis conditions, such as the initial ratio of the reactants, time, temperature, and the acid source, in addition to shearing flow, on particle morphologies were investigated. Fiberlike silicas of various lengths were obtained from a relatively wide range of synthesis conditions, while monodispersed rodlike silicas were prepared under very specific conditions. Each fiberlike product was found to be comprised of a bundle of fibers, with each fiber formed by the coupling of rodlike particles of almost identical size, irrespective of different synthesis conditions.

The dynamic adsorption/desorption behavior of volatile organic compounds (VOCs) such as toluene (C7H8) and benzene (C6H6) was evaluated for three kinds of mesoporous silicas of SBA-15, all having almost the same mesopore size of ca. 5.7 nm, and a MCM-41 silica with a smaller pore size of 2.1 nm using a continuous three-step test. The fiberlike SBA-15 silica exhibited exceptionally good breakthrough behavior, a higher VOC capacity, and easier desorption. The fiberlike silica was composed through the catenation of rodlike particles. The rodlike silicas, by comparison, were proven to be less useful in dynamic adsorption processes because of lower dynamic VOC capacities despite having comparative porous parameters with the fiberlike silica. The large dynamic VOC capacity of the fiberlike silica was attributed to the presence of a bimodal pore system consisting of longer, one-dimensional mesopore channels connected by complementary micropores.

Mesoporous and microporous monodispersed silica spheres have been prepared using a simple one-step synthetic procedure from an aqueous reaction mixture consisting of a commercial sodium silicate solution, various Pluronic triblock copolymers, and HCl or HNO3. The formation of porous silica spheres 130−225 μm in diameter was observed over a moderately wide range of reaction conditions. The pore structures of the resultant spheres lacked any long-range order, although they did exhibit outer textural uniformity. We concluded that the well-defined spherical morphology and pore sizes were the result of a combined effect of the EO/(EO + PO) block ratio and molecular weight of the Pluronics and the counteranions of the acid source.

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Thiol-functional porous silica spheres with 100-μm mean diameter were synthesized in one quick step for ca. 60 min at room temperature using 1-alkylamine templating through the S+X-I+ assembly pathway under an acidic condition. Thiol groups were introduced into materials while mesoporous silica spheres were prepared. SEM observation revealed that dodecylamine templating afforded a higher particle-shape quality than octylamine templating. Pore size and surface hydrophilicity of organic-functional silica spheres systematically decreased with increasing coverage of thiol groups on the pore surface, but the specific area was relatively constant. Thiol-functionalized silica spheres with 40% thiol loading resulted in microporous materials with hydrophobic pore surfaces for water vapor adsorption.