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1.
Bridged polysilsesquioxane xerogels containing amine (–NH2; –NH(CH2)2NH2; —NH) and thiol (–SH) groups were synthesized by hydrolytic polycondensation of 1,2-bis(triethoxysilyl)ethane, 1,4-bis(triethoxysilyl)benzene and appropriate trifunctionalized silanes in the presence of a fluoride-ion catalyst in an ethanol solution. 29Si CP/MAS NMR give indication of the molecular framework of these materials formed by structural T1, T2 and T3 units. 3-aminopropyl or 3-mercaptopropyl groups accessible to proton or metal ions are fixed to the xerogel surface by the siloxane bonds. IR and 13C CP/MAS NMR data clearly show that 3-aminopropyl groups form hydrogen bonds. The same data testify that all xerogels contain non-condensed silanol groups and some fraction of non-hydrolyzed ethoxygroups. Functionalized polysilsesquioxane xerogels obtained by means of organic spacers have a porous structure (500–1000 m2/g) and a high content of functional groups (1.0–2.7 mmol/g). AFM data indicate that xerogels are formed by aggregating primary particles—the size of such aggregates is in the range 30–65 nm. It was established that the main factors influencing the structure and adsorption properties considered hybrid materials are: the nature and geometrical size of the functional groups, spacer flexibility and, in some cases, the ratio of the reacting alkoxysilanes and the ageing time of the gel.  相似文献   

2.
Amorphous SiO2, TiO2 and xSiO2–(1–x)TiO2 ceramic materials with selected values of x 0.5, 0.7 and 0.9, have been prepared via sol-gel process using silicon tetraethoxysilane (TEOS) and titanium tetraisopropoxide Ti(OPri)4. By means of the combined use of differential thermal analysis (DTA),thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM),X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy(XAES), the surface microchemical structure and morphology of the sol-gel materials have been studied as a function of thermal treatments carried out in air up to 1200°C. In the range of temperature from 50 to 450°C, DTA-TG results evidence a remarkable mass loss due to the evaporation of organic solvents entrapped in the sol-gel materials and of the remnant organic components of the precursor metal alkoxides. In the range of temperature from 400 to about 1000°C, by means of the combined use of DTA, XRD, XPS and XAES techniques as a function of temperature and of chemical composition, it is possible to evidence the formation of crystalline phases such as quartz, anatase and rutile. Furthermore, line shape analysis of O1s XPS peak allows to distinguish between single O–Ti and O–Si bonds and also to disclose the presence of cross linking Si–O–Ti bonds, that act as bridges between SiO2and TiO2 moieties. As a function of temperature, Si–O–Ti bonds are broken and the formation of new Ti–O and Si–O bonds as in TiO2 and SiO2takes place as well as a silica segregation phenomenon. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
This tutorial review reports upon the organisation and functionalization of two families of hybrid organic-inorganic materials. We attempted to show in both cases the best ways permitting the organisation of materials in terms of properties at the nanometric scale. The first family concerns mesoporous hybrid organic-inorganic materials prepared in the presence of a structure-directing agent. We describe the functionalization of the channel pores of ordered mesoporous silica, that of the silica framework, as well as the functionalization of both of them simultaneously. This family is currently one of the best supports for exploring polyfunctional materials, which can provide a route to interactive materials. The second family concerns lamellar hybrid organic-inorganic materials which is a new class of nanostructured materials. These materials were first obtained by self-assembly, as a result of van der Waals interactions of bridged organosilica precursors containing long alkylene chains during the sol-gel process, without any structure directing agent. This methodology has been extended to functional materials. It is also shown that such materials can be obtained from monosilylated precursors.  相似文献   

4.
A dramatic change in the magnetic behaviour, which solely depends on the parity of the organic linker molecules, has been found in a family of layered CoII hydroxides covalently functionalized with dicarboxylic molecules. These layered hybrid materials have been synthesized at room temperature using a one-pot procedure through the epoxide route. While hybrids connected by odd alkyl chains exhibit coercive fields (Hc) below ca. 3500 Oe and show spontaneous magnetization at temperatures (TM) below 20 K, hybrids functionalized with even alkyl chains behave as hard magnets with Hc>5500 Oe and display a TM higher than 55 K. This intriguing behaviour was studied by density functional theory with the incorporation of a Hubbard term (DFT+U) calculations, unveiling the structural subtleties underlying this observation. Indeed, the different molecular orientation exhibited by the even/odd alkyl chains, and the orientation of the covalently linked carboxylic groups modify the intensity of the magnetic coupling of both octahedral and tetrahedral in-plane sublattices, thus strongly affecting the magnetic properties of the hybrid. These findings offer an outstanding level of tuning in the molecular design of hybrid magnetic materials based on layered hydroxides.  相似文献   

5.
The purpose of the present work is the sol–gel synthesis, structure characterization and potential application of hybrid biomaterials based on silica precursor (MTES) and natural polymers such as gelatin or pectin. The structure formation in the biomaterials was investigated by XRD, FTIR, BET and AFM. The results showed that all studied hybrid biomaterials have an amorphous structure. The FT-IR spectra of the obtained materials with MTES showed chemical bonds at 2,975, 1,255, 880 and 690 cm−1 due to the presence of Si–O–R (CH3 and C2H5) and Si–C bonds. In the samples synthesized with TEOS the inorganic and organic components interact by hydrogen bonding, Van der Waals or electrostatic forces. Surface area of investigated samples decreases with increasing of the natural polymers content. The structure evolution was studied by AFM and roughness analysis. Depending on the chemical composition a different design and size of particles and their aggregates on the surface structure were established. The hybrid biomaterials were used for immobilization of bacterial cells and applied in the biodegradation of the toxic compound 4-chlorobutyronitrile, possible constituent of waste water effluents in a laboratory glass bioreactor. Optimization of the process at different temperatures was carried out.  相似文献   

6.
This paper reports on recent progress in the synthesis of nanostructured siloxane-organic hybrids based on the self-assembly of amphiphilic silicon-based precursors. A variety of ordered hybrid materials have been obtained by molecular design of the precursors. Alkoxysilanes and chlorosilanes with covalently attached hydrophobic organic tails are hydrolyzed to form amphiphilic molecules containing silanol groups, leading to the formation of layered (lamellar) structures. Transparent and oriented thin films of lamellar hybrids were prepared by the reaction in the presence of tetraalkoxysilane. In addition, the design of molecules having alkyl chains and large oligosiloxane heads led to the formation of mesophases consisting of cylindrical assemblies, providing a direct pathway to ordered porous silica. The synthesis, structural features, and formation processes of these hybrid mesostructures are discussed.  相似文献   

7.
Conducting polymer based hybrid materials were synthesized by a new route. The use of pyrrole derivatives functionalized by a carboxylic acid or a -diketone group allows to control the polymerization rate of zirconium tetrapropoxide (Zr(OPr)4). The organic species entrapped in the resulting hybrid materials yield conducting polymers by electropolymerization. The results show that the formation of the conducting polymers depends on the nature of the monomer. Moreover, the presence of polysiloxane chains within the hybrid materials improves the properties of the latter.  相似文献   

8.
Molecular geometry, crystal packing and thermal stability of trans-1,4-cyclohexanedicarboxylic acid, 1,4-dibromo (I) are examined, in order to analyse the relative influence of the different intermolecular interactions at play. From a comparison with the corresponding properties of trans1,4-cyclohexanedicarboxylic acid (II), some insights on the results of the competition between Br and carboxylic groups are obtained. In the crystalline state, the molecules of both compounds present chair centrosymmetric geometry and build infinite chains through ring hydrogen bonds involving the carboxylic groups. These groups are axial in I and equatorial in II, giving rise to different assembly of the chains. In both compounds there is in general good agreement between the in-crystal geometry and the B3LYP/LanL2DZ optimized geometry of the corresponding isolated molecule. The only significant differences are related to the carboxylic groups. The intermolecular contacts in I have been rationalized on the basis of a graph set analysis. A molecular dynamics based method has been used to analyse the temperature dependence of the mean life time of the different kinds of hydrogen bonds characterized in I. It has been found that the O–H⋅ < eqid2 > ⋅O and C–H⋅ < eqid3 > ⋅O(carbonyl) interactions are the main source of thermal stability. The melting point of I determined within this approach agrees very well with the experimental value.  相似文献   

9.
Being exposed to hydrochloric acid vapor, solutions of a surfactant and sodium tungstate form tungstic-acid-based materials with a structure representing a system of interpenetrating hollow spheres 2–8 μm in diameter constructed from lamellar H2WO4 crystals with a thickness of 80–200 nm. The reduction of the tungstic-acid-based material with hydrogen gives rise to the formation of a material based on tungsten(IV) oxide (WO2), which retains the initial structure. The adsorption capacity of the tungstic-acid-based materials is determined with respect to benzene. The specific surface area of the obtained materials is 60–110 m2/g.  相似文献   

10.
The present contribution reports on our results concerning the synthesis of different binary and ternary oxide systems by using hybrid materials as “composite” precursors. In the last years, we have developed and explored a valuable strategy to yield a very homogeneous dispersion of nanoparticles of early metal transition oxide, MO2 (M = Zr, Hf) inside a silica matrix. This route is based on the use of the sol–gel process to obtain organic–inorganic hybrid silica-based materials embedding the oxide precursors (Zr and/or Hf oxoclusters), which are then calcined at high (T > 500 °C) temperatures to give the desired oxides. The “precursor” hybrid materials are prepared by a modified sol–gel process, involving the copolymerisation of the organically modified oxozirconium or oxohafnium clusters (M4O2(OMc)12 (M = Zr, Hf and OMc = methacrylate) with (methacryloxymethyl)triethoxysilane (MAMTES) or (methacryloxypropyl)trimethoxysilane (MAPTMS). Free radical copolymerisation of the 12 methacrylate groups of the oxoclusters with the methacrylate-functionalised siloxanes allows a stable anchoring of the oxoclusters to the silica network formed by the hydrolysis and condensation of the alkoxy groups. The sol–gel reactions of the two methacrylate-modified silanes methacryloxymethyltriethoxysilane and methacryloxypropyltrimethoxysilane were followed by using two independent time-resolved spectroscopic methods, viz., IR ATR and NMR with the aim to optimise their pre-hydrolysis times and consequently their use as precursors for hybrid materials. As mentioned, thermal treatment at high temperature of the hybrid yields a very homogeneous dispersion of ZrO2 and/or HfO2 nanoparticles in the silica matrix, since the molecular homogeneity of the starting hybrid is retained in the final mixed oxide. This route was successfully applied both to the synthesis of bulk materials and thin films characterised by different compositions (in term of M/Si molar ratios and M nature), heating route (conventional or microwave-assisted) and final temperature of annealing (from RT to 1,100 °C). The first example of the ZrO2–HfO2–SiO2 ternary oxide system was also prepared by this approach. The prepared systems, both in the form of hybrid materials as well as in the final form of binary or ternary oxides, were thoroughly characterised by a wide variety of analytical tools from a compositional, structural, morphological point of view. Moreover, in the case of the binary ZrO2–SiO2 bulk materials, also the evolution under heating was followed by different methods. In particular, the composition of the hybrid as well as of the final oxidic materials was determined by X-Ray Photoelectron Spectroscopy and elemental analysis, whereas FT-IR and multinuclear solid-state NMR spectroscopies shed light on the changes occurring in the composition upon thermal heating and the degree of condensation of the silica network. The morphology and the microstructure of the hybrids and of the oxides were studied by nitrogen sorption and Scanning Electron Microscopy. X-Ray Diffraction, Transmission Electron Microscopy and X-ray Absorption Fine Structure Spectroscopy X-ray Absorption Fine Structure Spectroscopy were used to follow the conversion of the amorphous oxides to the final materials consisting of crystalline zirconia or hafnia dispersed in amorphous silica. On selected systems, functional properties (surface reactivity, dielectric properties) were furthermore investigated. The obtained binary oxides were also used as substrates for functionalisation experiments with (1) dialkycarbamates and (2) long alkyl chains to produce functional materials for catalysis and HPLC applications, respectively.  相似文献   

11.
Micelle-templated mesoporous and organic–inorganic hybrid mesoporous materials are important in many fields of material research, especially for hosting catalysts in confined space. Among this class, the recent discovery of periodic mesoporous organosilicas (PMOs) represent an exciting new group of organic–inorganic nanocomposites targeted for a broad range of applications ranging from catalysis to microelectronics. Compared to the earlier generation of organic–inorganic hybrid mesoporous samples, obtained by the cocondensation reaction or by the grafting reaction, PMOs represent the right combination of organic and inorganic groups in the frame wall positions. This article reviews the current state of art in organic–inorganic hybrid mesoporous material research with special emphasis over periodic mesoporous organosilica materials having various redox centers (Ti, V, Cr) suitable for oxidation reactions as well as acidic sites (Al, –SO3H) for the organic transformation of bulky molecules.  相似文献   

12.
Abstract  A 1-D hybrid copper(I) halides, [(phen)Cu3I3] n (phen = 1,10-phenanthroline)(1) with novel D6R (double six-membered rings) Cu6I6 cores, was synthesized by solvothermal reaction and characterized by single-crystal X-ray diffraction. In 1, nitrogen atoms from phen replace two I of CuI4 tetrahedron to give distorted tetrahedral geometries (CuI2N2), then CuI2N2 tetrahedron shares corners via μ3-I to generate an extended 1-D zigzag chain. Two zigzag chains combines with one 1-D (Cu4I4) n chain containing D6R cores via μ3-I-Cu (from cores) bonds to form the infinite 1-D ribbonlike polymer along the a-axis. Furthermore, the title compound is stabilized by conspicuous C–H···I hydrogen bonds, π–π and d10–d10 metallic interactions. Experimental and theoretical optical property investigation indicates that 1 possesses semiconductor property. DFT calculation was executed to probe the electronic structure of 1. To our interest, phen act as a property control species with its π* electrons appear in the forbidden band. Graphical Abstract  A hybrid copper(I) halides [(phen)Cu3I3] n containing D6R cores was structurally determined, which was stabilized by conspicuous C–H···I hydrogen bonds, π–π and d10–d10 metallic interactions and possesses semiconductor property. DFT calculation indicate phen act as a property control species with its π* electrons appear in the forbidden band. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

13.
A new and universal synthetic strategy to hybridize metal oxides and conduct polymer nanocomposites has been proposed in this work. The simultaneous reaction process, which includes the generation of metal oxide layers, the oxidation polymerization of monomers, and the in situ formation of polymer–metal oxides sandwich structure is successfully realized and results in the unique hybrid polyaniline (PANI)‐intercalated molybdenum oxide nanocomposites. The peroxomolybdate proved to play a dual role as the precursor of the inorganic hosts and the oxidizing agent for polymerization. The as‐obtained hybrid nanocomposites present a flexible lamellar structure by oriented assembly of conductive PANI chains in the MoO3 interlayer, and thus inherit excellent electrical performance and possess the potential of active electrode materials for electrochemical energy storage. Such uniform lamellar structure together with the anticipated high conductivity of the hybrid PANI/MoO3 nanocomposites afford high specific capacitance and good stability during the charge–discharge cycling for supercapacitor application.  相似文献   

14.
Amphiphilic peptides bearing terminal alkyl tails form supramolecular nanofibers that are increasingly used as biomaterials with multiple functionalities. Insertion of alkylene chains in peptides can be designed as another type of amphiphilic peptide, yet the influence of the internal alkylene chains on self-assembly and biological properties remains poorly defined. Unlike the terminal alkyl tails, the internal alkylene chains can affect not only the hydrophobicity but also the flexibility and packing of the peptides. Herein, we demonstrate the supramolecular and biological effects of the central alkylene chain length inserted in a peptide. Insertion of the alkylene chain at the center of the peptide allowed for strengthened β-sheet hydrogen bonds and modulation of the packing order, and consequently the amphiphilic peptide bearing C2 alkylene chain formed a hydrogel with the highest stiffness. Interestingly, the amphiphilic peptides bearing internal alkylene chains longer than C2 showed a diminished cell-adhesive property. This study offers a novel molecular design to tune mechanical and biological properties of peptide materials.  相似文献   

15.
The objective of this work was to synthesize functionalized mesoporous silsesquioxanes with high concentrations of amine groups. During typical sol–gel syntheses, these materials are obtained by co-condensation of organic precursors with suitable linkers, such as tetraethoxysilane, necessary to prevent the mesoporous structure from collapsing. Thus, concentrations of amine groups in organosilicas usually do not exceed 2.7–3.4 mmol g−1. The use of bridged bis-trimethoxysilanes, however, allowed formation of mesoporous materials with no linker. Polycondensation of bis-trimethoxysilanes containing amine groups was conducted in acidic, neutral and basic media, resulting in high yields of solid bridged silsesquioxanes. Gelation occurred quickly if no acid or base was added to the reaction mixture. The hybrid organic/inorganic nature of obtained materials was confirmed by FT-IR and MAS CP NMR spectroscopy. Elemental analysis showed that amino group concentration in the products was 3.3–4.1 mmol g−1. Measurement of particle size distribution confirmed that choice of reaction media significantly affects particle sizes and agglomeration degrees, with the largest agglomerates (up to 50 μm) formed in basic media. A morphology study, using small-angle X-Ray scattering, displayed two-level fractal structures composed of aggregated 6.5–10.5 nm particles. Reactions in the presence of a surfactant resulted in formation of mesoporous structures. Furthermore, the obtained bridged silsesquioxanes were thermally stable down to 260 °C, but could reversibly absorb water and CO2 at temperatures below 120 °C. Thus, condensation of the bridged precursor without a linker resulted in formation of a highly functionalized mesoporous material.  相似文献   

16.
In this study, the formation of silica–chitosan hybrid materials via sol–gel process under pH values of 2–6 were investigated using N2 sorption analysis, scanning electron microscopy, transmission electron microscopy, thermal analysis and zeta potential analyzer. The hierarchical structure consisting of meso- and macropore was formed when pH value was higher than 2. Mesopores were formed as the interparticle channels of silica nanoparticles aggregates, whereas macropores were the void between the aggregates (clusters). The clusters size was decreased with increasing the pH value, resulting in the increase of the macroporosity. The thermal conductivity of the products was controlled in the range of 0.06 and 0.13 W m−1 K−1 by varying the product porosity between 88 and 69% (pH 6 and pH 2, respectively).  相似文献   

17.
Summary. Metal-alkoxides containing polymerizable groups are regularly used as precursors for inorganic–organic hybrid materials applying the combination of the sol–gel process and organic polymerizations. Here we report the synthesis of acetoacetoxy derivatives that are linked to methacrylate groups via alkyl chains of different chain length. The coordination of the resulting molecules to titanium- and zirconium-alkoxides (M(OR)4; M = Ti, Zr; R = ethyl, butyl, isopropyl) was investigated applying NMR and FT-IR measurements. The results were related to structural data of the dinuclear complex [Ti(O i Pr)3(EAA)]2 (HEAA: ethyl acetoacetate) which was obtained by single crystal X-ray diffraction. The study revealed that the β-keto ester groups acted as chelating ligands in all cases and thus polymerizable coordination compounds were formed. However, NMR analyses in solution showed that transesterification of the methacrylic-type monomers occurred even at mild conditions as a side reaction in a ratio which was found to be dependent on the type of metal alkoxide used.  相似文献   

18.
New crystalline nanostructured inorganic–organic hybrid materials containing isotactic polystyrene (iPS) are prepared by means of hydrosilylation coupling of vinyl‐terminated iPS with octakis(dimethylsilyloxy)silsesquioxane (Q8M8H). The number average molar mass of the iPS chains varies between 2000 and 6000 g mol?1. As a function of the iPS/Q8M8H ratio, using excess reagent, the formation of linear or star‐shaped hybrid architectures is achieved. Via fractionation, it is possible to isolate well‐defined linear hybrids containing one iPS chain and seven ethyl groups per silica core (iPS‐Q8M8E7) as well as star‐shaped hybrids containing up to eight iPS side chains (iPS6‐8‐Q8M8). These new iPS/polyhedral oligomeric silsesquioxane hybrid materials crystallize when the number average molar mass of iPS side chain exceeds 5500 g mol?1. The hydrosilylation coupling reaction and the resulting linear iPS‐Q8M8E7 and star‐shaped iPS6‐8‐Q8M8 are characterized by NMR spectroscopy, size exclusion chromatography (gel permeation chromatography), and polarized light microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013  相似文献   

19.
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.  相似文献   

20.
Summary. Silica-based inorganic–organic hybrid thin films embedding the organically modified oxohafnium clusters (Hf4O2(OMc)12, OMc=OC(O)–C(CH3)=CH2) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the pre-hydrolysed (methacryloxypropyl)trimethoxysilane (MAPTMS, (CH2=C(CH3)C(O)O)(CH2)3Si(OCH3)3). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by two different Si/Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin films were investigated through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth profiles performed on the thin layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica films and sharp film-substrate interfaces. Broad band dielectric spectroscopy (BDS) measurements permitted to investigate the electric response of the obtained films in the frequency and temperature range of 40 Hz – 1 MHz and 0–160°C.  相似文献   

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