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1.
A technique based on the29Si NMR spectra for analyzing the spatial structure of cyclolinear polymethylsiloxanes has been developed. The role of certain factors influencing the formation of the spatial structure of the chains during the preparation of these polymers has been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1460–1466, August, 1993. 相似文献
2.
The SiO2 thin films were prepared by a process which combines a sol-gel method and photoirradiation. The HF etch rate and microhardness of a film prepared by this process were better than those of a film furnace-fired at same temperature. The Raman and 29Si solid state NMR spectra of film prepared by this process were similar to those of a film furnace-fired at higher temperature. There are many unstable folded non-linear SiO2 species in the film prepared at low temperature. On treatment at higher temperature, unstable folded non-linear Si-O-Si rearranges to the stable linear Si-O-Si bond. Photoirradiation enhances this structure change. The process provided denser and harder SiO2 thin films, even at low temperature, than the conventional furnace-firing method did. 相似文献
3.
Karl Hassler 《Monatshefte für Chemie / Chemical Monthly》1982,113(4):421-425
A simple preparation of the title compounds is achieved by reacting Na3P/K3P with stoichiometric mixtures of chlorotriphenylsilane and chlorotrimethylsilane.31P- and29Si-NMR-Data as well as Ir and Raman spectra of the compounds are reported. 相似文献
4.
The reactivity of tetraethoxysilane (TEOS) used in many sol-gel syntheses can be increased by prehydrolysis. In contrast to one-step prehydrolysis acidic two-step prehydrolysis causes an increase of the reactivity of the low molecular species provided the total water/TEOS ratios are the same in both cases. By choice of the processing conditions of the hydrolysis—shown on variation of water content, hydrolysis steps and heat treatment—the degree of condensation, the ratio of hydrolyzable (-OC2H5) and hydrolyzed groups (-OH) and the structure of the low molecular species (short chains, 3-membered and 4-membered rings) can be influenced systematically. The development of the building units formed in the early reaction stages is ascertained by molybdate method and 29Si NMR measurements. 相似文献
5.
G. Anbalagan G. Sankari S. Ponnusamy R. Thilak kumar S. Gunasekaran 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):404-409
Sanidine, a variety of feldspar minerals has been investigated through optical absorption, vibrational (IR and Raman), EPR and NMR spectroscopic techniques. The principal reflections occurring at the d-spacings, 3.2892, 3.2431, 2.9022 and 2.6041 Å confirm the presence of sanidine structure in the mineral. Sanidine shows five prominent characteristic infrared absorption bands in the region 1200–950, 770–720, 590–540 and 650–640 cm−1. The Raman spectrum shows the strongest band at 512 cm−1 characteristic of the feldspar structure, which contains four membered rings of tetrahedra. The UV–vis–NIR absorption spectrum had strong absorption features at 6757, 5780 and 5181 cm−1 due to the combination of fundamental OH– stretching. The bands at 11236 and 8196 cm−1and the strong, well-defined band at (30303 cm−1 attest the presence of Fe2+ and Fe3+, respectively, in the sample. The signals at g = 4.3 and 3.7 are interpreted in terms of Fe3+ at two distinct tetrahedral positions Tl and T2 of the monoclinic crystal structure The 29Si NMR spectrum shows two peaks at −97 and −101 ppm corresponding to T2 and T1, respectively, and one peak in 27Al NMR for Al(IV). 相似文献
6.
Q. Deng W. Jarrett R. B. Moore K. A. Mauritz 《Journal of Sol-Gel Science and Technology》1996,7(3):177-190
Perfluorosulfonic Acid (PFSA)]/[Organically-Modified Silicon Oxide (ORMOSIL)] hybrids were formulated via sol-gel reactions of mixtures of tetraethoxysilane (TEOS) and diethoxydimethylsilane (DEDMS) in the nanophase-separated morphology of a PFSA membrane (Nafion®). The molecular structures of the ORMOSIL phases were investigated by 29Si solid state NMR spectroscopy and the spectra compared with those of corresponding bulk ORMOSILs. PFSA-in situ ORMOSIL composition can be tailored by manipulating TEOS/DEDMS source solution composition and quantified by 29Si solid state NMR spectroscopy. Copolymerization of TEOS and DEDMS monomers, rather than block formation, occurs within the PFSA as well as in the bulk. As DEDMS feed concentration increases, ORMOSIL nanostructures are more hydrophobic and more flexible. Dimethylsiloxane rings are dominant in PFSAs in which hydrolysis + condensation of pure DEDMS occurs. 相似文献
7.
T. Woignier C. Fernandez-Lorenzo J. L. Sauvajol J. F. Schmit J. Phalippou R. Sempere 《Journal of Sol-Gel Science and Technology》1995,5(3):167-172
The structure of the silica aerogels was studied by Raman spectroscopy. The spectra of the solid network resembles that of bulk silica with additional bands related to organic groups and a large amount of OH groups.The typical bands due to ring breathing also called defect bands D
1 and D
2 located at 490 and 610 cm–1 are present. However, the evolution of the D
2 band compared to that of OH band (980 cm–1) seems apparently, in contradiction with the results previously reported in the literature. During heat treatments between 25 and 300°C the D
2 and the OH bands increase simultaneously. Generally, in silica glass the defect band D
2 grows at the expense of the OH groups.This result is explained by the oxidation of the organic compounds which, in this temperature range, leads to the formation of the both species (OH) and those related to siloxane rings. 29Si MAS NMR results are in agreement with the Raman study. 相似文献
8.
Afifa Hafidh Fathi Touati Faouzi Hosni Ahmed Hichem Hamzaoui Sayda Somrani 《Phosphorus, sulfur, and silicon and the related elements》2018,193(3):155-163
New hybrid materials were synthesized from an inorganic precursor, (tetraethoxysilane: TEOS) and bifunctional organic precursors through the sol-gel process. Indeed, monolithic and transparent hybrid gels were obtained by the reaction of tetraethoxysilicate (TEOS) with 1,2,4-thiadiazole-3,5-diamine (1), 5-amino-1,3,4-thiadiazole-2-thiol (2), and 1H-1,2,4-triazole-3-thiol (3) in ethanol as solvent, using chloric acid (HCl 10?1M) as catalyst. It is shown that TEOS has been cross-linked with bi-functional heterocyclic compounds: (1), (2) and (3) leading to the formation of transparent and colorous gels. The characterization was realized by infrared, 29Si and 13C CP MAS NMR. The xerogels morphology and texture were studied by scanning electron microscopy (SEM) and Brunauer – Emmet – Teller method (BET). The obtained results show that organic adducts (1), (2) and (3) react with TEOS leading to gels in which Si–N and Si–S bridges were formed. According to N2-physisorption results, xerogels are mesoporous with specific surface area varied from 105 to 312 m2g?1 and their isotherms are classified as type IV. The optic and magnetic properties of hybrids were studied respectively by UV-Vis spectroscopy and RPE. This study showed that all materials are paramagnetic semiconductors. 相似文献
9.
29Si MAS NMR spectra of natural melanophlogite as well as of synthetic melanophlogite indicate that the room temperature lattice structure has lower symmetry than expected from its proposed crystal structure. On heating the samples to temperatures above room temperature, the structure undergoes a reversible phase transition with a transition temperature characteristic of the locality. For the synthetic melanophlogite, the transition is over the range 298 K to 338 K. From low temperature NMR spectra it is concluded that the low temperature forms of synthetic melanophlogite and of melanophlogite from Sicily differ in their crystal lattice symmetries due to their characteristic guest species.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.On leave Mineralogisches Institut, CAU KIEL, FRG 相似文献
10.
L. S. Kosheleva 《Russian Chemical Bulletin》1994,43(3):346-350
The change in the structure of NH4NaY zeolite (53 % NH4
+, Si/Al = 2.37) after hydrothermal treatment at 873 K followed by modification with aqueous KOH solution at 353 K was studied by IR and29Si NMR spectroscopy. It has been shown that hydrolytic cleavage of the Al-O bond of the deammoniated zeolite sites by hydrothermal treatment predominates in the framework groups Si(OAl)
n
(OSi)4–n
,n=2, 3. Molecular water adsorbed on such a sample exists as hydrogen-bonded associates with hydrogen bonds of various strengths reaching that in ice-like structures (the band at 2468 cm–1). Treatment with an alkali results in partial regeneration of the normal bridge bonds. The exchange of the protons of the terminal silanol groups with the alkaline cation prevents those groups from participating in the regeneration process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 387–391, March, 1994. 相似文献
11.
Karl Hassler 《Monatshefte für Chemie / Chemical Monthly》1988,119(10):1051-1056
The synthesis and properties of [Ph
2
p-TolSi]2, [Ph
2
p-TolSi]2SiPh
2, [Ph
3
Si]2Si(p-Tol)2, [Ph
2
p-TolSi]2Si(p-Tol)2 and (SiPh
3)2SiH2 are described. The silanes are identified using IR,Ra- and29Si-NMR-spectroscopy. 相似文献
12.
Summary Silicon substituted organostannyl silanes are formed by the reaction of stannylallyl silanes with triflic acid and from stannyl-hydrogen silanes and CHBr3. The structures have been proved by NMR-investigations.
Herrn Prof. Dr.E. Hengge zum 65. Geburtstag gewidmet 相似文献
13.
Zhang Zhengping Gorman B.P. Dong Hanjiang Orozco-Teran Rosa A. Mueller D.W. Reidy R.F. 《Journal of Sol-Gel Science and Technology》2003,28(2):159-165
Dimethyldiethoxysilane (DMDES) appears to be a very promising modifier to introduce functional groups to a silicate network. The polymerization and cyclization of DMDES under acid-catalyzed conditions (DMDES : Ethanol : water : HCl = 1:4:4:3.68 × 10–4 in molar ratio) were investigated by high resolution liquid 29Si nuclear magnetic resonance (NMR) and Fourier transform infrared spectrometry (FTIR). Time-dependent NMR and FTIR data illustrate that monomers of (CH3)2Si(OC2H5)2, (CH3)2Si(OC2H5)(OH), and (CH3)2Si(OH)2 reach meta-equilibrium in less than 4 minutes. 3-membered rings ((CH3)2SiO)3 appear about half an hour later and 4-membered rings ((CH3)2SiO)4 an hour later, which continue to be formed over 24 hours. The relative concentrations of monomers, linear structures and cyclic structures suggest a modified model for the kinetics of cyclization, where 4-membered rings are formed by dimer-dimer interactions, as opposed to monomer-trimer interactions previously proposed. 相似文献
14.
Li YS Wang Y Tran T Perkins A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3032-3037
Organosilane sol-gels have been prepared under different conditions from mercaptopropyltrimethoxysilane (MPTMS) and mercaptopropyltriethoxysilane (MPTES). These sol-gels were applied for the thin film coating on aluminum. Vibrational spectroscopy has been employed to trace and to study the proceeding of the sol-gel formation and the curing of the coated films on Al. Based on the group frequencies as well as their spectral behavior under different conditions, vibrational assignments have been made for most of the observed bands. Surface enhanced Raman scattering has revealed the chemical adsorption of MPTMS sol-gel on silver particles. Recorded reflection and absorption infrared (RAIR) spectra of coated tiles cured at different temperatures have indicated that surface reaction may occur at high temperature. The anticorrosion characters of the coated metals have been evaluated with the measured electrochemical data. Results from cyclic voltammographs have indicated that each layer of sol-gel coating would reduce the redox current across the electrode/electrolyte solution interface. Tafel plots have shown that the anodic current of the coated electrode decreases significantly and the corrosion potentials shift to the positive side. 相似文献
15.
Miewon Jung 《Journal of Sol-Gel Science and Technology》2000,19(1-3):563-568
The systematic modifications of silica matrix as a function of modified Ti-alkoxide contents (Au nanocrystals doped TiO2/SiO2 mixed oxide thin films) have been investigated by the sol-gel process. A structural analysis on the various steps of the hydrolysis-condensation process as well as solid powder is determined by IR, UV-Visible, and 29Si NMR spectroscopy. 29Si MAS spectra are characterized by broad lines for the three types of sites. Different distributions (Q
2, Q
3, and Q
4 units) observed in the TiO2/SiO2 (1 : 3) sample. Proper control of the process condition, modifying the Ti alkoxide as a less reactive precursor, improves the increase the amount of Ti–O–Si bonding in the silica network of TiO2/SiO2 mixed oxide matrices and the distribution of metal oxides. This method can be used for the preparation of homogeneous metal and metal-metal alloy nanocrystals deposition from mixed oxide thin films. 相似文献
16.
Giles M. Prentice Liam M. Emmett Henghua Zhu Gabriele Kociok-Köhn 《Supramolecular chemistry》2016,28(1-2):161-167
We report here the synthesis and study of naphthalenediimide–siloxane polymers with high thermal stability. Two of the five polymers investigated could be developed into recyclable materials. We use solid-state 29Si NMR to evaluate the degree of cross-linking and polymerisation in our materials. 相似文献
17.
A phosphorus-containing tri-ethoxysilane (dopo-icteos) reacting from the nucleophilic addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (dopo) and 3-(trieoxysilyl) isocyanate (icteos) was synthesized. The structure of dopo-icteos was confirmed by 1H, 13C, 31P NMR and IR spectra. A triethylamine catalyzed mechanism for the dopo-icteos synthesis was proposed and verified by NMR spectra. The phosphorus-containing epoxy/SiO2 and polyimide/SiO2 nanocomposites were prepared from the in-situ curing of diglycidyl ether of bisphenol A (DGEBA)/4,4-diaminodiphenylmethane(DDM)/dopo-icteos, and imidization of poly(amic acid) of pyromellitic dianhydride (PMDA)/4,4′-oxydianiline (ODA)/dopo-icteos, respectively. The microstructure and morphology were investigated by 29Si NMR, scanning electron microscope (SEM), EDS (Si and P mapping) analysis and atomic force microscope (AFM). The thermal properties, flame retardancy and dielectric properties of the organic-inorganic hybrids were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), limiting oxygen index (LOI), thermal gravimetric analysis (TGA) and dielectric analyzer (DEA). 相似文献
18.
Robert J. P. Corriu Joël J. E. Moreau Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》1994,2(1-3):87-91
An alternative route to organosilsesquioxanes by hydrolytic condensation of the Si-H bonds of trihydrosilanes is described. This method avoids the formation of alcohols or acids since the leaving group is removed as hydrogen gas. The influence of the catalyst, ClRh(PPh3)3 or fluoride anion, on the properties of the resulting materials is discussed. 相似文献
19.
Sophie de Monredon–Senani Christian Bonhomme François Ribot Florence Babonneau 《Journal of Sol-Gel Science and Technology》2009,50(2):152-157
This paper addresses two questions related to functionalization of silica particles: (1) is the grafting of hydrophobic organoalkoxysilanes on a silica surface possible in water-rich medium and (2) how to prove the formation of covalent bonds with the surface? Trimethylethoxysilane, dimethyldiethoxysilane and methyltriethoxysilane have been reacted with precipitated silica in water-rich medium (water/ethanol 25/75 v/v) and 29Si MAS NMR was used to answer both questions: 29Si chemical shift values of the organosilicon units in the case of trimethylethoxysilane and dimethyldiethoxysilane clearly distinguished between self-condensation reactions and surface reactions through covalent bonds. 相似文献
20.
L. V. Morozova O. A. Tarasova A. I. Mikhaleva M. V. Markova G. F. Myachina B. A. Trofimov 《Russian Chemical Bulletin》1997,46(11):1855-1858
1-Allenylpyrroles are polymerized under the conditions of thermal (60 °C) and radical initiation at both 1,2- and 2,3-positions
of the allenyl group to form soluble reactive polymers with various ethylenic, including polyvinylic, fragments. The possibility
to prepare 1-allenylpyrrole copolymers has been demonstrated using 1-vinylpyrrolidone and ethylene glycol vinylglycidyl ether
as an example. Doped layers based on poly-1-allenyl-4,5,6,7-tetrahydroindole are photosensitive.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1958–1961, November, 1997. 相似文献