Nanostructured carbon/silica hybrid materials and poly(furfuryl alcohol)/silica xerogel are prepared and characterized here. In the key synthetic step, cation‐induced polycondensation of furfuryl alcohol occurs simultaneously with a sol–gel process involving tetraethoxysilane and water to yield the xerogel, which is subsequently thermally transformed to the carbon/silica material (see Figure).
Mullite is an aluminosilicate of the composition Al 2 (Al 2ϩ2x Si 2Ϫ2x)O 10Ϫx with x generally ranging between 0.2 and 0.5. XRD and 29 Si and 27 Al nuclear magnetic resonance (NMR) have been used to investigate the structure of various mullite compositions (x ϭ 0.26, 0.36, 0.42, and 0.69) as well as sillimanite (x ϭ 0) and ␥-Al 2 O 3 (x ϭ 1). 27 Al magic angle spinning (MAS) NMR of the central and satellite transitions have been used to determine the chemical shifts and quadrupole interaction parameters for the various AlO 4 and AlO 6 units. The isotropic chemical shifts of the various units are 5.9 ppm for AlO 6 , 69.1 ppm for AlO 4 (T), 55.0 ppm for AlO 4 (TЈ), and 45.7 ppm for AlO 4 (T*) where AlO 4 (T) denotes the aluminum tetrahedra in the double chains, and AlO 4 (TЈ) and AlO 4 (T*) those next to the oxygen Oc*. Quantitative numbers of the aluminum occupancy of these sites have been determined for the various powder samples. These results are in good agreement with the average structure model of mullites. NMR and XRD proved the presence of impurities of kyanite in natural sillimanite and of ␥-Al 2 O 3 in the mullites with x ϭ 0.42 and 0.69.
Cationic guest polymerizations of several vinyl monomers inside the pores of HY zeolites
and MCM-41 as hosts have been used for the synthesis of novel organic/inorganic hybrid
materials. Substituted vinyl ethers [ROCHCH2; R = −CH2CH(CH3)2, −C2H5, −C2H4Cl,
−C6H11], 2,3-dihydrofuran, and N-vinylcarbazole can serve this purpose, because their
polymerization can be initiated by the active protons in HY zeolite or by coadsorbed
arylmethylium ions in MCM-41. The synthesis of well-defined poly(vinyl ethers) or poly(vinylcarbazole) under the conditions of constricted geometry can be achieved by means of
cationic host−guest polymerization of the corresponding monomers in MCM-41 (pore
diameter 3.6 nm) with (4-CH3OC6H4)2CHCl (MeO) or (C6H5)3CCl (TC) as the internal surface
initiator. The reaction products are novel polymer/MCM-41 host−guest hybrid materials.
The molecular mass of the (enclosed) polymer and the percentage of polymer within the
pores of MCM-41 as well as HY zeolite can be adjusted within certain limits. Polymeric
products are analyzed by solid-state magic angle spinning cross-polarization 13C{1H} NMR
spectroscopy and gel permeation chromatography analyses of the obtained polymer fraction
after dissolution of the hybrid material in an aqueous potassium hydroxide solution. The
formation of conjugated sequences of poly(vinyl ether) segments inside the HY zeolites is
caused by successive ether cleavage along the encapsulated polymer chains.
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