Hexagonal to Mesocellular Foam Phase Transition in Polymer-Templated Mesoporous Silicas

Lettow, John S.; Han, T. Yong-Jin; Schmidt‐Winkel, Patrick; Yang, Peidong; Zhao, Dongyuan; Stucky, Galen D.; Ying, Jackie Y.

doi:10.1021/la000660h

Cited by 413 publications

(341 citation statements)

References 24 publications

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“…In the synthesis of large-pore SBA-15, when the weight ratio of the most used swelling agent, TMB, 7-9 to P123 was above 0.3, hexagonal to mesocellular foam phase (MCF) transition happened and disordered MCFs were obtained even in the presence of NH 4 F, 8 which are templated by oil-in-water micromulsion. 9 However, in our experiments excess decane will not lead to the phase transition but instead may build discrete spaces within the synthesis mixture and thus confine the formation of silicate-doped micelles. As a result, the side-on condensations between short silicate-doped micelles are preferred; thus a new kind of SBA-15 with channels running parallel to the short axis was built (see Scheme 1).…”

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confidence: 68%

Unusual Mesoporous SBA-15 with Parallel Channels Running along the Short Axis

et al. 2004

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Submicrometer-sized mesoporous silica SBA-15 with cuboidlike morphology has been prepared by using excess amounts of decane as cosolvent in the presence of NH 4 F. The channels of the resulting material run parallel to the short axis of the cuboidlike SBA-15, which had not been previously reported. It has also been found that the materials have a well-ordered channel structure with pore size ca. 12 nm.Due to their uniform pore structure and high surface areas, mesoporous materials such as MCM-41 and SBA-15 have been studied extensively in the fields of catalysis, separation, adsorption, and even the fabrication of semiconductor or low dielectric devices. 1 Methods to tune the morphology, 2,3 pore size, 4-9 and particle size 10-15 of the mesoporous materials have long been the target of various groups. Organic cosolvents such as 1,3,5-trimethylbenzene (TMB), alkanes, and amines, etc. are often used to tailor the pore size of mesoporous materials, such as the cationic surfactanttemplated MCM-41 materials. Among the alkanes used, decane has been proven to be a good swelling agent, though the obtained mesoporous silica materials are often disordered. 6 Well-ordered mesoporous materials with short channels have attracted great attention because they are favorable for mass transfer. Control of the channel's length could be attained by decreasing the particle size or making the parallel orientation of channels running along the short axis. Nanoparticles of cationic surfactanttemplated mesoporous materials such as MCM-41 have been obtained by changing the composition of starting materials, 11,12 by using a double surfactant system, 13 or by quenching the reaction by adding HCl. 14 The synthesis of nanosized SBA-15 is rarely reported. Typical SBA-15 materials have rope-like morphologies with a relatively uniform length of ∼1 µm and the channels running parallel to the long axis of the rope. 4 At the same time, SBA-15 with other morphologies such as fiberlike and doughnutlike, which have curving and even orbicular channel structures, 3 are also unfavorable for the mass transfer in separation and catalysis. Here, we present for the first time the synthesis of submicrometer-sized mesoporous silica SBA-15 with parallel channels running along the short axis. It has been attained by using large amounts of decane as the cosolvent in the presence of NH 4 F during synthesis. Recently, this new type of material with short channels has been applied in the assembly of highly dispersed Ag nanoparticles in our laboratory. The obtained catalyst was evaluated in methane conversion, which exhibited good activity and stability at 773 K.As a typical synthesis procedure, 2.4 g of EO 20 PO 70 EO 20 (P123) was dissolved in 84 mL of HCl solution (1.07 M) and then stirred at room temperature until the solution became clear. Different amounts of decane (C 10 H 22 ) (with weight ratios of decane to P123 ranging from 0:1 to 7.6:1) were then added into the solution. The mixture was stirred at room temperature for at least 1 h. Finally, 0.027 g of N...

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confidence: 68%

Unusual Mesoporous SBA-15 with Parallel Channels Running along the Short Axis

et al. 2004

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“…41 (MCM-41) and its precursor with template (MCM-T, without calcination), Santa Barbara Amorphous-15 (SBA-15) and mesocellular foam (MCF) were prepared inhouse as per the procedure reported in the literature [17][18][19].…”

Section: Experimental Materialsmentioning

confidence: 99%

Mesoporous silica reinforced polybutadiene rubber hybrid composite

et al. 2016

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Polybutadiene rubber (BR) hybrid composites reinforced with mesoporous silica (MPS)/nanoclays, silica and MPS/carbon black were prepared. The primary focus of this research was to incorporate the mesoporous silicate (MPS), e.g., mobil composition of matter (MCM-41) as reinforcing filler in the BR matrix. The textural properties of the mesoporous materials were characterized by powder X-ray diffraction (XRD), transmission electron microscopy and N 2 isothermal adsorption measurements. The quantity of MCM-41 in the BR matrix was first optimized and the similar optimized quantity of different MPS was compared in terms of tensile strength. The composites were characterized by XRD and scanning electron microscopy. The composite containing 10 phr-loaded MCM-41 showed 250 % improvement in tensile strength compared to the matrix devoid of nanomaterial. The effects of co-incorporation of two different kinds of nanomaterials having different nanostructures, e.g., layered montmorillonite and particulate MCM-41 were also studied. MCM-41 enhanced the mechanical strength of BR almost double the value compared to precipitated silica at the same filler loading. The morphological features of the composites were well corroborated with the mechanical properties.

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“…The big pore size and large pore volume is considered as desirable characteristic in the adsorption or catalysis applications especially when organics with bulky molecules are involved as adsorbates or reactants owing to facilitated mass transfer [3]. In recent years, much effort has been devoted to further expanding the porosity of SBA-15, and the general method was the utilization of swelling agents such as aromatics [1,[4][5][6] or alkanes [7][8][9][10], which could dissolve in the hydrophobic core of template micelles to make enlarged hydrophobic volume, leading to bigger pore size and larger pore volume. Large pore volume of up to 2.2 cm 3 /g was achieved with the use of mesitylene as swelling agent [1].…”

Section: Introductionmentioning

confidence: 99%

Expanding mesoporosity of triblock-copolymer-templated silica under weak synthesis acidity

Tian

et al. 2009

Journal of Colloid and Interface Science

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a b s t r a c tWith initial aging at low temperature for enough time, silicas with large mesoporosity were synthesized using triblock copolymer as template agent under weak acidities. SBA-15 with periodic mesostructure and short mesochannels could be synthesized at pH 2.5-3.0 within weak acidity range, and the surface areas, pore diameters and pore volumes reached up to ca. 1000 m 2 /g, 8.8 nm and 2.0 cm 3 /g, respectively, which were significantly higher than those of the conventional SBA-15 synthesized under strong acidities. Mesoporous silica with wormhole structure and abundant textural porosity was formed at pH $ 3.5. The increased hydrophobic volume of the copolymer micelles at elevated pH values was responsible for the enlargement of mesoporosity in the products. The materials synthesized under weak acidities showed lower hexagonal ordering in comparison to the general SBA-15 synthesized under strong acidities because the decreased hydronium ion concentration induced relatively weaker assembly forces during the synthesis. Nonetheless, the short mesochannels and large pore diameter in the products might be beneficial to some applications in which fast diffusion of molecules is required.

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Hexagonal to Mesocellular Foam Phase Transition in Polymer-Templated Mesoporous Silicas

Cited by 413 publications

References 24 publications

Unusual Mesoporous SBA-15 with Parallel Channels Running along the Short Axis

Unusual Mesoporous SBA-15 with Parallel Channels Running along the Short Axis

Mesoporous silica reinforced polybutadiene rubber hybrid composite

Expanding mesoporosity of triblock-copolymer-templated silica under weak synthesis acidity

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