Self‐Assembly of Alkyl‐Substituted Cubic Siloxane Cages into Ordered Hybrid Materials

Abstract

Siloxane-organic hybrids with well-ordered mesostructures were synthesized through the self-assembly of novel amphiphilic molecules that consist of cubic siloxane heads and hydrophobic alkyl tails. The monoalkyl precursors functionalized with ethoxy groups (C(n)H(2n+1)Si(8)O(12)(OEt)(7), 1 Cn, n=16, 18, and 20) were hydrolyzed under acidic conditions with the retention of the siloxane cages, leading to the formation of two-dimensional hexagonal phases by evaporation-induced self-assembly processes. Analysis of the solid-state (29)Si MAS NMR spectra of these hybrid mesostructures confirmed that the cubic siloxane units were cross-linked to form siloxane networks. Calcination of these hybrids gave mesoporous silica, the pore diameter of which varied depending on the alkyl-chain length. We also found that the precursors that had two alkyl chains formed lamellar phases, thus confirming that the number of alkyl chains per cage had a strong influence on the mesostructures. These results expand the design possibility of novel nanohybrid and nanoporous materials through the self-assembly of well-defined oligosiloxane-based precursors.

Hybrid Porous Materials with High Surface Area Derived from Bromophenylethenyl‐Functionalized Cubic Siloxane‐Based Building Units

“…Uptakes of up to 1.19 wt % at 77 K and 760 Torr and initial isosteric heats of adsorption as high as 8.0 kJ molhomogeneity from predefined D4R units involved surfactant-directed co-assembly of D4R cages, [9] cross-linking of D4R units by hydrosilylation, [10] polycondensation of alkoxysilylated cages, [11] and self-assembly of well-designed amphiphilic molecules containing D4R cages. [12] Although claims were made that D4R units were retained in the siloxane networks, control over the microscopic arrangement of the cages and subsequent micropore size distribution remains to be achieved.…”

“…Progress toward locally ordered structures has been made in recent years, mainly by self-assembly of well-defined oligomers as molecular building units. [8][9][10][11][12] Among oligomeric siloxane units, the cubic octameric siloxane cage Si 8 O 12 , commonly termed double four-ring (D4R), is of particular interest as an ideal molecular building unit because of its rigidity, hyperbranched architecture, high symmetry, and ease of functionalization. [13] D4R moieties bearing specific functional groups such as aldehyde, carboxyl, and epoxy have been used in diverse forms as model catalysts, components for polymer blends, organic light-emitting diodes, and so on.…”

Fabrication of silsesquioxane-based nano-wrinkled structures by coupling the polymeric surface onto rigid templates assembled from unique deca-silsesquioxane

“…Bridged silsesquioxanes turn out to be able to form interesting nano-scale structures through self-assembly, such as tubular structures and semicylindrical shells, the interactions of which can be cooperative covalent and noncovalent. [11][12][13][14][15][16][17][18] For example, silsesquioxane-based Janus particles proved to self-organize into ordered hierarchical structures resulting from the diverse properties of the cages; 10 and cross-linking of octakisphenyl silsesquioxane could provide a uniform nanosphere morphology template for fabricating well-defined microporous carbons. [11][12][13][14][15][16][17][18] For example, silsesquioxane-based Janus particles proved to self-organize into ordered hierarchical structures resulting from the diverse properties of the cages; 10 and cross-linking of octakisphenyl silsesquioxane could provide a uniform nanosphere morphology template for fabricating well-defined microporous carbons.…”

Synthesis of New Polyfunctional Cage Oligosilsesquioxanes and Cyclic Siloxanes by Thiol-ene Addition

“…They may serve as cores for the generation of star branched, hyperbranched and dendritic branched polymers [1][2][3] and may be used for the cross-linking of linear polymers to produce various polymer networks [4][5][6][7]. They may also be important precursors in sol-gel technology for the generation of various porous and bulk materials [8][9][10][11]. Cage polysilsesquioxanes of regular polyhedral structure bearing many functional groups are used for the construction of composite materials for various applications such as catalysts, nano-reactors, sensors, metal absorption [12][13][14][15] etc.…”