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Rod-like and spherical mesoporous SBA-15 silica particles were synthesized as pure silicas and surface modified by organosilane coupling agents firstly, and then the effects of these mesoporous materials on the critical micelle concentration (CMC) of sodium dodecylsulfate (SDS), the stabilities of batch and semi-continuous MMA emulsion polymerizations, and the molecular weights and molecular weight distributions of the polymer products were studied. The incorporation of both unmodified and silane-modified forms of the mesoporous silica particles in the polymerization reaction increased the CMC of SDS. The presence of the unmodified mesoporous silica in the polymerization process led to instability in the batch emulsion polymerization process, as indicated by the formation of increased amounts of coagulum, and a decrease in the molecular weight of the polymer product. However, in comparison to the polymer formed in the absence of particle additives the molecular weight of the PMMA polymer increased with the amount of emulsifier and the addition of silane-modified SBA-15 particles, suggesting the growth of the polymer chains is facilitated at least in part by reaction in the pores of the particles. The improvement in molecular weight indicates that semi-continuous MMA emulsion polymerization is best suited for the preparation of PMMA-mesoporous silica composites., INTRODUCTION Since the discovery of hexagonally ordered mesoporous molecular sieves silicas at the beginning of the 1990s, the synthesis and application of the advanced mesoporous materials have undergone rapid growth. [...]

The proton transfer process mediated by water molecules adsorbed in an aluminosilicate framework was studied using ab initio molecular dynamics simulations. The investigation was conducted using a quasi-one-dimensional model simulating the mesoporous aluminosilicate channel structures.

A novel three-step assembly pathway is reported for the formation of a mesostructured alumina with framework pore walls made of crystalline, lathlike gamma-Al203 nanoparticles. The high surface areas (300-350 m2/g) and pore volumes (0.45-0.75 cm3/g) provided by these mesostructured forms of gamma-Al203 are useful in materials and catalytic applications where the availability of surface Lewis acid sites and the dispersion of supported metal centers govern reactivity.

A grafting process has been found to be effective in producing sieves that bind quantitatively more heavy metal ions than standard techniques. The sieves were made using covalent grafting of 3-mercaptopropylsilyl groups MCM-41 and HMS to the framework pore walls. The functionalized HMS derivative has found to bind more mercury (II) ions than the initially anionic MCM-41 derivative.

A novel assembly approach was used to prepare a porous lamellar silica with a hierarchical structure (MSU-V). This involved the cooperative formation of multilamellar vesicular surfactant-silica complexes, through the H-bondong interactions between H2N(CH2)12-NH2 as products of the tetraethylorthosilicate. Sorption properties of the lamellar MSU-V silica were similar to pillared lamellar clays.

The physical and catalytic properties of two titanium-substituted mesoporous catalysts prepared at ambient temperatures via electrostatic and neutral assembly pathways were compared. Specifically, Ti-MCM-41 and Ti-HMS molecular sieves were characterized with respect to their catalytic function in the liquid phase peroxide oxidations of methyl methacrylate, styrene, and 2,6-di-tert-butylphenol. The results demonstrated their superior catalytic efficiency over other titanium silicates.

Templating processes that mimic biomineralization have attracted considerable attention because of their potential uses in the design of valuable inorganic materials (1),(2). Similar processes based on the hydrolysis and cross-linking [...]

Mesoporous silica molecular sieves have been prepared by the hydrolysis of tetraethylorthosilicate in the presence of low-cost, nontoxic, and biodegradable polyethylene oxide (PEO) surfactants, which act as the structure-directing (templating) agents. This nonionic, surfactant-neutral, inorganic-precursor templating pathway to mesostructures uses hydrogen bonding interactions between the hydrophilic surfaces of flexible rod- or worm-like micelles and Si[(O[C.sub.2][H.sub.5]).sub.4-x][(OH).sub.x] hydrolysis products to assemble an inorganic oxide framework. Disordered channel structures with uniform diameters ranging from 2.0 to 5.8 nanometers have been obtained by varying the size and structure of the surfactant molecules. Metal-substituted silica and pure alumina mesostructures have also been prepared by the hydrolysis of the corresponding alkoxides in the presence of PEO surfactants. These results suggest that nonionic templating may provide a general pathway for the preparation of mesoporous oxides., The discovery by Mobil researchers (1) of the M41S family of mesoporous molecular sieves with pore sizes from 1.5 to 10 nm has stimulated interest in the potential use of [...]

The templated synthesis of mesoporous molecular sieves in the interlayer spaces of clays is possible by the intercalated surfactants which along with aqueous silicate species form an interlayer silica framework. The surfactant is withdrawn by calcination resulting in a mesoporus solid with thermally stable pores of 14 to 22 Angstroms thickness. These porous clay heterostructures are applied for patterning heterogeneous catalysts.

A neutral templating route for preparing mesoporous molecular sieves is demonstrated based on hydrogen-bonding interactions and self-assembly between neutral primary amine micelles (S°) and neutral inorganic precursors (I°). The S° I° templating pathway produces ordered mesoporous materials with thicker framework walls, smaller x-ray scattering domain sizes, and substantially improved textural mesoporosities in comparison with M41S materials templated by quaternary ammonium cations of equivalent chain length. This synthetic strategy also allows for the facile, environmentally benign recovery of the cost-intensive template by simple solvent extraction methods. The S° I° templating route provides for the synthesis of other oxide mesostructures (such as aluminas) that may be less readily accessible by electrostatic templating pathways., Mobil Oil Corporation researchers discovered the M41S family of mesoporous molecular sieves from a self-assembly process involving electrostatic interactions between positively charged quaternary ammonium micelles and inorganic anions as framework [...]

Mesoporous silica-based molecular sieves partially replaced with titanium are manufactured by templating. Titanium silicate materials exhibit catalytic activity toward oxidation of phenolic compounds and the transformation of benzene to phenol. The titanium silicate is a perfect molecular sieve catalyst in oxidizing alkanes and phenols.

X-ray diffraction, TGA-DTA, and (super 7)Li and (super 23)Na NMR data is presented for PEO nanocomposites made with natural and synthetic montmorillonite clays that provide new insight into interlayer structure. (super 23)Na NMR shows that PEO intercalculation results in the conversation of the multiple Na(super +) hydration states observed for the prostine clay into inner sphere sites most likely formed through coordination with the basal oxygens of the clay.

The mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function analysis of synchroton X-ray powder diffraction data and by Raman spectroscopy is investigated. The Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading.

The density functional theory (DFT) method is used to investigate the structure and bonding of silica and aluminosilicate nanoclusters containing five- and six-membered oxygen rings. The results reveal that an excitation energy at least 18 times larger than the room-temperature thermal energy is needed to break the stable five-membered ring structure, implying a high hydrothermal stability and acidity for this aluminosilicate structure.

The structure determination and an extensive exploration of the opportunities in the pore structure tailoring for a prominent member of ordered silicas with cage-like mesoporous structure (OSCMS) family are reported. It is shown that the temperature and time control during the synthesis allows one to gradually change cage-like pores of FDU-1 to a highly open and accessible porous system with narrow pore size distribution.

Two-dimensional, hexagonally ordered silicas with large uniform mesopores are assembled through a nonionic supramolecular assembly pathway using sodium silicate as a silica source and the triblock copolymer pluronic as a structure-directing agent. The materials exhibited adsorption properties highly similar to silica assembled through an electrostatic pathway under strongly acidic conditions, indicating the framework structure of analogues and consist of ordered large pores connected by micropores in the pore walls.

Thiol moieties which were grafted to the pore channel walls of mesoporous silica molecular sieves produced very effective heavy metal ion adsorbents which poses opportunities for operators of waste treatment and cleanup campaigns. Heavy metals such as lead and mercury are known to pollute the environment significantly to the detriment of natural ecosystems and human communities. Framework mesostructures that have many surface hydroxyl groups and huge pore channel parameters help develop framework channels which maintain appreciable open-framework features and various functional locations.

The replacement of amorphous aluminosilicated by derivatives of zeolite Y in gas oil cracking catalysts 40 years ago resulted in better product distribution, less coke formation, better stability, and lower catalyst consumption rates. Nanosized MSU-AS compositions possess the unique combination of mesoporosity, hydrothermal stability, acidity, and longevity that is desired for the efficient cracking of high molecular weight hydrocarbons.

A general route to mesostructured alumina containing transition alumina phase is reported. The study shows that surface areas are compatible with the values expected for a mesostructure with thick walls.

Aluminosilicate mesostructures that are steam stable were assembled from zeolite type Y seeds.

A family of mesoporous molecular sieves (denoted MSU-G) with vesiclelike hierarchical structures and unprecedented thermal (1000 ° C) and hydrothermal stabilities (more than 150 hours at 100 ° C) associated with high Si[O.sub.4] crosslinking was prepared through a supramolecular assembly pathway that relies on hydrogen bonding between electrically neutral gemini surfactants of the type [C.sub.n][H.sub.2n+1]NH[([CH.sub.2]).sub.2] [NH.sub.2] and silica precursors derived from tetraethylorthosilicate. The vesicle shells are constructed of one or more undulated silica sheets that are about 3 nanometers thick with mesopores (average diameters from 2.7 to 4.0 nanometers) running both parallel and orthogonal to the silica sheets, which makes the framework structure bicontinuous and highly accessible. Catalytic metal ion centers [for example, Ti(IV) and Al(III)] have been incorporated into the framework with the retention of hierarchical structure., Substantial progress has been made recently in extending the supramolecular assembly of mesostructured inorganic framework structures to include hierarchical forms with a variety of particle shapes (1-3). Mesoporous metal oxide [...]