Generalized synthesis of periodic surfactant/inorganic composite materials

Abstract

THE recent synthesis of silica-based mesoporous materials by the cooperative assembly of periodic inorganic and surfactant-based structures has attracted great interest because it extends the range of molecular-sieve materials into the very-large-pore regime. If the synthetic approach can be generalized to transition-metal oxide mesostructures, the resulting nanocomposite materials might find applications in electrochromic or solid-electrolyte devices, as high-surface-area redox catalysts and as substrates for biochemical separations. We have proposed recently6 that the matching of charge density at the surfactant/inorganic interfaces governs the assembly process; such co-organization of organic and inorganic phases is thought to be a key aspect of biomineralization. Here we report a generalized approach to the synthesis of periodic mesophases of metal oxides and cationic or anionic surfactants under a range of pH conditions. We suggest that the assembly process is controlled by electrostatic complementarity between the inorganic ions in solution, the charged surfactant head groups and—when these charges both have the same sign—inorganic counterions. We identify a number of different general strategies for obtaining a variety of ordered composite materials

General Synthesis of Ordered Nonsiliceous Mesoporous Materials

“…Polar organic solvents, such as C 2 H 5 OH or CH 3 OH, are recommended for their oxygen donating property to improve the proton transferring within the synthetic system. The various mesostructured phases can be synthesized by tuning ratios of inorganic species to surfactants, or by using different surfactants, which are in agreement with previous synthesis pathways ( 48,50). Figure 5 shows the examples of synthesizing various mesoporous metal phosphates through fundamental routes A to E and their derivatives.…”

“…As generally accepted, the organicinorganic interaction between organic templates and inorganic precursor species is the main driving force to form ordered silicate mesostructures (48,49). Elaborate investigations on mesoporous materials have been focused on understanding and utilizing the organic-inorganic interactions.…”

“…Elaborate investigations on mesoporous materials have been focused on understanding and utilizing the organic-inorganic interactions. Stucky and coworkers proposed four general synthetic routes which are S + I", ST + , S^XI* and S'X + I" (S + = surfactant cation, S" = surfactant anion, I + = precursor cation, I" = precursor anion, X + = counterion cation and X" = counterion anion), respectively, as shown in Figure 2 (48). A series of ordered nonsiliceous mesostructured solids (e.g, tungstate and molybdate) were prepared.…”

Nanostructured silica templated by double hydrophilic block copolymers with a comb-like architecture

“…Contrary to microporous materials synthesized around isolated molecules, the MPO are elaborated around supramolecular assemblies of autoassociative molecules. The first structures of MPO, of MCM-41 type, were obtained by using micelles of surfactants made up of an alkyl chain and a cationic polar head [3]. Those materials have a limited thickness of the walls, pore sizes lower than 10 nm and have a low thermal stability.…”

Hierarchical Porosity in Self‐Assembled Polymers: Post‐Modification of Block Copolymer–Phenolic Resin Complexes by Pyrolysis Allows the Control of Micro‐ and Mesoporosity

“…[20,21] Among the various concepts, the template-assisted approach provides a facile way for well-defined structures at different length scales, for a wide range of pore sizes, and for various chemical functionalities. [5,16,[22][23][24] Examples of suitable structure-directing agents include, surfactants or block copolymers, [25][26][27][28][29][30][31] colloids, [32,33] emulsions, [34] polymer gels, [35] vesicles, [36] foams, [13,37] solid particles, and bacteria. [38] By combining different structure-directing agents, the structures can be controlled hierarchically at different independent length scales.…”