Design of nanohybrid and nanoporous materials through self-assembly of organosilane molecules

Abstract

Structural control of silica-based materials prepared by sol-gel chemistry is important from both fundamental and practical viewpoints. This paper reviews our work on the synthesis of ordered siloxane-based nanomaterials by self-assembly of organosilane-based precursors. Lamellar siloxane-organic hybrids with various structures, macroscopic morphologies, and properties have been prepared from long-chain alkyltrialkoxysilanes or organoalkoxysilane-tetraalkoxysilane mixtures by selfassembly during hydrolysis and polycondensation. Furthermore, the molecular design of novel alkylsiloxane precursors having a large oligosiloxane head led to the formation of hybrid mesostructures consisting of cylindrical assemblies that gave ordered microporous or mesoporous silica by calcination. These results open a new self-assembly route to the design of ordered nanoporous materials as well as nanohybrid materials without the use of any templates or structure-directing agents.

Controlled pore formation in organotrialkoxysilane-derived hybrids: from aerogels to hierarchically porous monoliths

“…77,78 A sophisticated approach to tailor ordered mesoporous materials only from trialkoxysilanes is demonstrated and reviewed by Shimojima and Kuroda. 79,80 They hydrolyzed amphiphilic alkyltrialkoxysilanes (with C 12 -C 18 ) in acidic media to obtain crystalline alkylsilanetriols and the subsequent drying step allows solid-state polycondensation to yield mesostructured hybrids with the lamellar symmetry (Fig. 4).…”

Reversibly meltable layered alkylsiloxanes with melting points controllable by alkyl chain lengths

“…In contrast, a three-step process, hydrolysis as the first step followed by the self-assembly and slow polycondensation, has been proposed as the mechanism of the formation of layered alkylsiloxanes at RT and under acidic conditions. 6,7,13,19,23,30,31 The long alkyl chains are considered to aggregate in the reaction media with the relatively hydrophilic solvent (EtOH) because of van der Waals' force and hydrophobic interactions. The aggregation is considered to form the monolayer assemblies 6,19 rather than the bilayer arrangement.…”

Solvent Evaporation Assisted Preparation of Oriented Nanocrystalline Mesoporous MFI Zeolites

“…An evaporation-induced assembly is an effective way to produce mesoporous materials with ordered mesophase. − In the past, organoalkoxysilanes have been found to undergo evaporation-induced self-assembly and form mesophases with mostly lamellar and occasionally hexagonal structures. However, only amorphous pore walls are produced. − A combination of solvent evaporation induced self-assembly with hydrothermal zeolite growth will pave new ways to control crystallization and will provide new methods to tailor hybrid materials. This approach can be scaled up to meet commercial processing, and can be adapted for recyclable solvents. , …”