Nano Building Blocks via Iodination of [PhSiO_1.5]_n, Forming [p-I-C₆H₄SiO_1.5]_n (n = 8, 10, 12), and a New Route to High-Surface-Area, Thermally Stable, Microporous Materials via Thermal Elimination of I₂

Abstract

We describe the synthesis and characterization of the homologous p-iodophenylsilsesquioxanes (SQs) [p-I-C(6)H(4)SiO(1.5)](n) (n = 8, 10, 12) via ICl-promoted iodination (-40 to -60 degrees C) with overall yields of 80-90% and > 95% para selectivity following recrystallization. Characterization by NMR, FTIR, TGA, and single-crystal X-ray diffraction are reported and compared to data previously published for I(8)OPS. Coincidentally, we report a new synthesis of the elusive pentagonal decaphenyl SQ (dPS) [C(6)H(4)SiO(1.5)](10) and its characterization by NMR and single-crystal X-ray studies. These unique macromolecules possess equivalent chemical functionality but varying symmetries (cubic, pentagonal, and D(2d) dodecahedral), offering the potential to develop homologous series of functionalized star and dendrimer compounds with quite different core geometries and thereby providing the potential to greatly vary structure-property relationships in derivative compounds and nanocomposites made therefrom. We find that all three compounds decompose on heating to approximately 400 degrees C/N(2) with loss of I(2) to form robust, microporous materials with BET surface areas of 500-700 m(2)/g, pore volumes of 0.25-0.31 cm(3)/g, average pore widths of 8 A, and oxidative stabilities > or = 500 degrees C and with solid-phase morphologies varying from crystalline to mostly amorphous, as indicated by powder XRD and SEM studies. These latter findings point to important symmetry effects relating directly to packing in the crystalline phase prior to thermolysis.

Tailor‐Made Hybrid Organic–Inorganic Porous Materials Based on Polyhedral Oligomeric Silsesquioxanes (POSS) by the Step‐Growth Mechanism of Thiol‐Ene “Click” Chemistry

“…[4] Polyhedral oligomeric silsesquioxanes (POSS) have the basic structure (RSiO3 = 2 ) n , (n = 8, 10, 12). These are organic-inScheme 1. a) vinylPOSS (RSiO3 =2 ) n shown for n = 8, 10, 12; b) variety of thiol compounds explored in this study; the nomenclature attributed to the linker is identical to the respective polymer; and c) hybrid polymer 1 prepared with vinylPOSS and linker 1. organic hybrid, cage-like nanostructures (e.g., Scheme 1 a) that, in their chemical diversity, have already been used as building blocks for the generation of porous materials through thermolysis [5] and hydrosylation, [6] as well as other coupling reactions. [7] The preparation of monolithic porous materials involving POSS has often been addressed with amines, [8] and through uncontrolled, free-radical copolymerization with other monomers.…”

Novel phenyl‐POSS/polyurethane aqueous dispersions and their hybrid coatings

“…15,36 The increased effect for hybrids can be explained in two ways. On the one hand, according to the Vyazovkin model, 42 the enhancement of the thermal stability of POSS=PU polymers is caused by the suppression of the molecular mobility of polymer chains by bulky phenyl-POSS.…”

“…3 With the special R groups, phenyl-POSS exhibit more interesting and unique properties. 15 Zheng et al used octaaminophenyl-POSS as crosslinking agents to react with PU prepolymers to form octa-armed, star-like POSS=PU hybrids. 16 The advantages of phenyl-POSS are readily apparent, as the finished polymer has been modified by it with excellent mechanical strength, heat resistance, oxidation resistance, and decreased flammability.…”

High Surface Area, Thermally Stable, Hydrophobic, Microporous, Rigid Gels Generated at Ambient from MeSi(OEt)3/(EtO)3SiCH2CH2Si(OEt)3 Mixtures by F−‐Catalyzed Hydrolysis

“…Many highs urface area organic materialss uch as hyper-cross-linked styrene-divinylbenzene copolymers are made by the porogen methodw ith surface areas approaching 2000 m 2 g À1 .S ilsesquioxaneb ased materials fit into the second synthetic methodology,w hereby porosity introduction employs the monomer geometry coupled with controlled polymerization. [13][14][15][16][17][18][19][20][21] Most high surfacea rea materials containing silicon are made via sol-gelp rocessing of tri-and tetraalkoxysilanes. [22][23][24][25] Solgel processing employs acid-or base-catalyzed hydrolysis and condensation to form highly cross-linkedx ero-or aerogels depending on the drying method.…”

“…Gel materials offer SSA'so fu pt o1 300 m 2 g À1 some of the highest known systemsb ased on SQs. [15][16][17][18][19][20][21][22][23][24] Gel materials also offer solvent uptake up to 600 %b ymass. Vinyl groups can be incorporated into the systemso ffering post polymerization functionalization points and further crosslink density,e xtending the useful possibilities for these materials.…”