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11.
H.?Hussain H.?U.?Rehman Z.?AhmadEmail author 《Journal of Sol-Gel Science and Technology》2005,36(3):239-248
Nano-composites from aramid-silica system have been prepared via sol-gel process. Poly (phenyleneterephthalamide) copolymer
chains were prepared by reacting a mixture of p- and m-phenylenediamines with terephthaloyl chloride in dimethylacetamide used as solvent. The sol-gel process in the polymer
matrix was carried out through hydrolysis and condensation of a mixture of tetraethoxysilane and (3-glycidoxypropyl) trimethoxysilane.
The latter was used to develop linkage, on one hand with silica network structure using alkoxy groups and on the other hand
with aramid chains at its secondary amine groups through glycidal groups of silane. Mutual interaction between the two disparate
phases aramid and silica network was thus created. Thin films of the composites containing different proportions of silica
ranging from 5.0 to 25.0-wt% were cast by the solvent elution technique. The α-relaxation temperature associated with the
glass transition was measured by the dynamic mechanical thermal analysis. The results showed an increase in the glass transition
temperature from 328°C for the pure aramid to 352°C for the hybrid materials containing 25-wt% silica, an indicative of the
increased interfacial interaction between the two phases. Films having relatively low silica content were flexible and transparent,
but those with high silica content were opaque and brittle. These films were tested for their tensile strength, modulus and
toughness. The mechanical strength of the composites as compared to the pure aramid increased initially but with further addition
of silica the strength decreased. The initial increase can be explained due to increased interfacial interaction between the
two phases, however agglomeration of silica particles was responsible for decreasing strength at higher silica contents. 相似文献
12.
Inorganic-organic hybrids have been synthesized by incorporation of the inorganic component of Ti(OC2H5)4 into the organic polymer of ethyl cellulose. The inorganic-organic hybrids did not dissolve in toluene used as a solvent for the starting materials. The ethanol was formed as a by-product of the alcoholysis condensation reaction between Ti(OC2H5)4 and ethyl cellulose. These results suggest that ethoxy groups of Ti(OC2H5)4 react with hydroxy groups of ethyl cellulose to form cross-linking bonds of –O–Ti–O–. The reaction of Ti(OC2H5)4 with ethyl cellulose was further investigated by Fourier transform infrared (FT-IR) spectroscopy. The FT-IR spectroscopic experiments revealed that the Ti–O bond state of Ti(OC2H5)4 was changed by refluxing a toluene solution of Ti(OC2H5)4 with ethyl cellulose. The inorganic-organic hybrids have an interesting dielectric property; their dielectric constant is higher than that of ethyl cellulose and that of a simple mixture of TiO2 and ethyl cellulose. 相似文献
13.
Synthesis of Highly Porous Organic/Inorganic Hybrids by Ambient Pressure Sol-Gel Processing 总被引:6,自引:0,他引:6
This paper reports the synthesis of highly porous organic/inorganic hybrids by a two-step acid-base catalyzed sol-gel process and ambient pressure drying. In the method organic and inorganic precursors are copolymerized so as to incorporate organic ligands into the solid network. The two-step acid-base catalyzed process was used to prevent phase segregation during the hydrolysis and co-condensation of organic and inorganic precursors. The organic ligands incorporated into the solid gel network modify the surface chemistry. Thus, the wetting angle is significantly increased so that the collapse of the gel network is greatly reduced upon the removal of pore fluid during drying. Organic/inorganic hybrids with BET surface areas above 1250 m2/g, porosities above 75% and pore sizes of 8 nm have been synthesized. 相似文献
14.
Young-Joo Eo Duk-Jun Kim Byeong-Soo Bae Ki-Chang Song Tae-Young Lee Seung-Won Song 《Journal of Sol-Gel Science and Technology》1998,13(1-3):409-413
Tetraethylorthosilicate (TEOS)/vinyltriethoxysilane (VTES) hybrid materials were prepared and the hydrolysis and condensation reactions during processing were investigated by means of 29Si NMR solution spectroscopy. The variation of drying characteristics of the coating films was examined with respect to the tetraethylorthosilicate (TEOS)/vinyltriethoxysilane (VTES) ratio, as well as drying temperature, by FT-IR spectroscopy. It is shown that the TO mode of Si–O–Si stretching absorption was enhanced with increasing tetraethylorthosilicate (TEOS) content and drying temperature. Also, the wettability of the coating films on polymer films was independent of the solution composition but enhanced by the precoating of poly(4-hydroxystrene) (PHS) as a wetting agent. The adhesion between the coating and the films was also enhanced when the vinyltriethoxysilane (VTES) content in the coating solution was increased. 相似文献
15.
A capillary zone electrophoresis (CZE) method for the analyses of kaempferol in Centella asiatica and Rosa hybrids and rutin in Chromolaena odorata was developed. The optimization was performed on analyses of flavonoids (e.g., rutin, kaempferol, quercetin, myricetin, and apigenin) and organic carboxylic acids (e.g., ethacrynic acid and xanthene-9-carboxylic acid) by investigation of the effects of types and amounts of organic modifiers, background electrolyte concentrations, temperature, and voltage. Baseline separation (R(s) = 2.83) of the compounds was achieved within 10 min in 20 mM NaH2PO4 - Na2HPO4 (pH 8.0) containing 10% v/v ACN and 6% v/v MeOH using a voltage of 25 kV, a temperature of 30 degrees C, and a detection wavelength set at 220 nm. The application of the corrected migration time (t(c)), using ethacrynic acid as the single marker, was efficient to improve the precision of flavonoid identification (% relative standard deviation (RSD) = 0.65%). The method linearity was excellent (r2 > 0.999) over 50-150 microg/mL. Precision (%RSD < 1.66%) and recoveries were good (> 96% and %RSDs < 1.70%) with detection and quantitation limits of 2.23 and 7.14 microg/mL, respectively. Kaempferol in C. asiatica and R. hybrids was 0.014 g/100 g (%RSD = 0.59%) and 0.044 g/100 g (%RSD = 1.04%), respectively, and rutin in C. odorata was 0.088 g/100 g (%RSD = 0.06%). 相似文献
16.
17.
18.
Dr. Chen Xue Shu Wang Prof. Dr. Wen-Long Liu Prof. Dr. Xiao-Ming Ren 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(20):5280-5287
A direct band gap 2D corrugated layer lead chloride hybrid, [(CH3)4N]4Pb3Cl10 ( 1 ), shows analogous topology to the {Mg3F104−}∞ layer in Cs4Mg3F10, and with the (CH3)4N+ cations locating in the inorganic layer voids and between the interlayers. Two reversible structural phase transitions occur in 1 at 225/210 K and 328/325 K upon heating/cooling, respectively. On going from the low- to intermediate-temperature phase, the space group changes from P21/c to Cmca, and the crystallographic axis perpendicular to the layers is doubled with the order–disorder transformation of (CH3)4N + cations between the interlayers. The intermediate- and high-temperature phases are isomorphic with similar cell parameters and packing structure; their main difference concerns the disorder degree of the (CH3)4N + cations between the interlayers. The two-step structural phase transitions lead to dielectric anomalies around the corresponding Tc. Interestingly, 1 shows multiband emission, originating from the recombination of exciton and emission of defects. Moreover, 1 exhibits divergent thermochromic luminescent features around the Tc on the intermediate to low temperature transition. 相似文献
19.
20.
A novel inorganic-organic hybrid compound, {[Co(dien)]4[0aO4)MoV8(wV10.56MoV10.44)4- O33(OH)3]}'nH20 (1, n = 1, dien = diethylenetriamine), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the triclinic system with a = 11.927(2), b = 13.328(3), c = 19.306(4)A, a = 93.76(3), β = 94.14(3), γ = 109.99(3)°, V= 2863.2(12) A3, space group P1 and Z = 2 at 173 K. The final full-matrix least-squares refinement converged to R = 0.049 for 9621 observed reflections with 1 〉 2σ(I) and wR = 0.139 for all data (9871) and S = 1.073. Crystal structure analysis shows that 1 contains a kind of the first reported mixed-valence and molybdenum-tungsten mixed-distributed e-Keggin structural polyanion capped by four Co(dien) fragments with the main group element P occupying the center site. These results were further confirmed by energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Thermogravimetry (TG) and X-ray photoelectron spectroscopy (XPS) analyses. 相似文献