Templating mesoporous silica crystals

Figure 1. Schematic pathway for preparing surfactant-templated mesoporous silicas, illustrating a formation mechanism based on preformed liquid crystal (LC) mesophase (route A) or a cooperative process (route B). Reprinted from [20], Copyright (2008) WILEY-VCH Verlag GmbH Co.

Goltner, C. G Henke, S. Weissenberger, M. C. Antonietti, M. 1998. Mesoporous silica from lyotropic liquid crystal polymer templates. Angew. Chem. Int. Ed. 37 613-616. 

For mesoporous silica (pore 0>2O A), successful results were obtained by the synthesis of the MCM family of silicates and aluminosilicates (of Section II.B). Their preparation is achieved by liquid crystal templating and micellar phases (hexagonal MCM-41, cubic MCM-48, laminar MCM-50)36,37 and further developments are currently reviewed38. 

In addition to recent advances in block co-polymer templating of periodic mesoporous silica and silica colloidal crystal templating of periodic mesopo-rous polymers [79], SAMs have been used for polymer patterning [80]. Mixtures of two strongly incompatible polymers, a polystyrene (PS)-polyvinylpyridine (PVP) blend, were found to phase separate when placed on a... 

Davidson (2002) Mesoporous silica Structure evolution, role of templates crystallization variables + + n.a. Synthesis of mesoporous silica with defined properties... 

It seems to be possible that most transition metal oxides can be made in porous crystals with different morphologies using various mesoporous silicas as templates. It is expected that these materials have potential in applications such as catalysis, fuel cell, gas sensors and Li-batteries. Their physical properties would fall in between nanoparticles and bulk specimens, although our knowledge about these properties is still very limited. 

Two-dimensional DQ H MAS-NMR spectra were used to investigate the local structure of a surfactant-templated silicate thin film.498 Silicalite-1 powders (20-1000 nm. crystals) were characterised by 29Si MAS-NMR spectroscopy.499 13C and 29Si solid-state NMR data were used to characterise organic-inorganic mesoporous silica-based materials.500... 

Two kinds of template, viz. hard template and soft template, are usually available for nanocasting processes. The true liquid crystal templating synthesis can be considered a soft-template process. In general, the hard template means an inorganic solid. For example, mesoporous silica as a template to replicate other materials, such as carbon or metal oxides, by which the pore structure of the parent can be transferred to the generated porous materials. A 3-D pore network in the template is necessary to create a stable replica. Mesoporous silica and carbon are commonly used templates for nanocasting synthesis. 

S.A. El-Safty and T. Hanaoka, Microemulsion Liquid Crystal Templates for Highly Ordered Three-dimensional Mesoporous Silica Monoliths with Controllable Mesopore Structures. Chem. Mater., 2004, 16, 384 100. 

Mesoporous Ti-MCM-41 support was prepared by hydrothermal crystallization according to literature procedure [23]. Disordered mesoporous titanosilicate Ti-Meso was synthesized by modified sol-gel method and hydrothermal crystallization (at 100°C, 5 days) and using cetyltrimethyl ammonium bromide as template following the procedure similar to that for the synthesis of disordered mesoporous silica [24]. A modified sol-gel method without hydrothermal crystallization was used to prepare mesoporous titanosilicates, TiO-SiO(l) and TiO-SiO(2) [25]. Ti grafting on Ti-MCM-41 support was carried out according to literature procedure [26]. 

Sen T, Tiddy GJT, Casci JL, Anderson MW (2004) Synthesis and characterization of hierarchically ordered porous silica materials. Chem Mater 16 2044 Deng Y, Liu C, Yu T, Liu F, Zhang F, Wan Y, Zhang L, Wang C, Tu B, Webley PA, Wang H, Zhao D (2007) Facile synthesis of hierarchically porous carbons from dual colloidal crystal/block copolymer template approach. Chem Mater 19 3271 Luo Q, Li L, Yang B, Zhao D (2000) Three-dimensional ordered macroporous structures with mesoporous silica walls. Chem Lett 29 378... 

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