氨基硅烷偶联剂对蒙脱石的修饰改性研究

研究了氨基硅烷偶联剂对蒙脱石的修饰改性,并和长链烷基硅烷偶联剂作对比.通过改性前后蒙脱石的傅立叶红外光谱(FT-IR),广角X射线衍射(WAXD),热失重分析(TGA)研究发现,在冰醋酸的处理下,氨基硅烷偶联剂不但能够对蒙脱石进行表面偶联修饰而且能够以插层剂的形式进入蒙脱石的层间.初步的浸润/分散性实验结果表明:氨基硅烷插层/表面修饰改性的蒙脱石在弱极性乙醇溶剂中的分散性能明显提高.     

Erbium Luminescence in Suboxide Films Derived from Triethoxysilane

Silicon nanoclusters formed in triethoxysilane during annealing at temperatures above 900°C are used for increasing the excitation cross section of Er atoms. A stronger sensitization of the Er luminescence is observed, for a given Er concentration, when the Er³⁺ ions are introduced in the matrix by ion implantation than when adding a salt to the precursor solution, because of a better dispersion of the implanted atoms. The logarithmic increase of the emission yield with the Er concentration up to 1 at% which is found in the case of implanted samples is ascribed to the quenching processes by interaction between neighbour Er³⁺ ions.     

Organolead Halide Perovskite Nanocrystals: Branched Capping Ligands Control Crystal Size and Stability

CH₃NH₃PbBr₃ perovskite nanocrystals (PNCs) of different sizes (ca. 2.5–100 nm) with high photoluminescence (PL) quantum yield (QY; ca. 15–55 %) and product yield have been synthesized using the branched molecules, APTES and NH₂‐POSS, as capping ligands. These ligands are sterically hindered, resulting in a uniform size of PNCs. The different capping effects resulting from branched versus straight‐chain capping ligands were compared and a possible mechanism proposed to explain the dissolution–precipitation process, which affects the growth and aggregation of PNCs, and thereby their overall stability. Unlike conventional PNCs capped with straight‐chain ligands, APTES‐capped PNCs show high stability in protic solvents as a result of the strong steric hindrance and propensity for hydrolysis of APTES, which prevent such molecules from reaching and reacting with the core of PNCs.     

两种新型多孔金属-有机凝胶的合成、表征与气体吸附性能

以1,4-二(3-乙酰丙酮基)苯(DAB)为有机配体分别与铝离子和铬离子反应,合成出2个新型的金属-有机凝胶:Al-湿凝胶和Cr-湿凝胶,通过直接干燥法得到相应的2种多孔干凝胶:Al-干凝胶和Cr-干凝胶.通过X射线粉末衍射仪(PXRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FTIR)、热重分析仪(TGA)、X射线能谱仪(EDS)和氮气吸附-脱附仪对凝胶材料的结构和形貌进行了表征.结果显示,2种多孔金属有机凝胶材料是由球状纳米粒子堆积而成,具有较高的比表面积、丰富的微孔及少量的介孔结构.气体吸附性能测试结果表明,Al-干凝胶的比表面积为790.3 m2/g,在1.01×105Pa,77 K下能够吸附117.45 cm3/g的氢气,在273 K下能够吸附60.74 cm3/g的二氧化碳.     

Synthesis of (Hyper)Branched Monohydroxyl Alkoxysilane Oligomers toward Silanized Urethane Prepolymers

The aim of this work was the synthesis of (hyper)branched oligomers based on trialkoxysilane in various conditions and further application of them in order to modify the urethane prepolymers. Hydroxyl-terminated trialkoxysilane was used as a monomer for homo-condensation. It was obtained by reaction of 3-aminopropyl trialkoxysilane (APTES) with ethylene carbonate (EC). The reaction was based on the attack of amine at the carbonyl carbon atom followed by ring opening of the carbonate to give a urethane (carbamate) product. The next step was the condensation via substitution of ethoxy groups on silicon atom with the terminal hydroxyalkyl groups present in the primary product with the evolution of ethanol. Accordingly, the impact of temperature and type of catalyst on process efficiency was investigated. A quantitative analysis of reaction progress and products of the conversion of EC together with ethanol evolution was conducted by means of gas chromatography, which allowed us to determine the formation of monomeric product and, indirectly, of oligomeric products. It was found that at room temperature after 24 h, the majority of the monomeric product was isolated, whereas at elevated temperature in the presence of Ti-based catalyst, further condensation of the monomer into branched oligomers was preferred, and, moreover, the application of vacuum intensified that process. The obtained products were structurally characterized by ¹H and ²⁹Si NMR, MALDI-ToF and Gel Permeation Chromatography. Finally, two different alkoxysilane products, monomeric and oligomeric, were applied for modification of urethane prepolymer, forming silanized one (SPUR). The influence of the silanizing agent on the mechanical and thermal properties of the moisture-cured products was shown before and after additional conditioning in water.     

Organic surface modification and analysis of titania nanoparticles for self-assembly in multiple layers

The characteristics of TiO₂ coatings can greatly influence their final performance in large-scale applications. In the present study, self-assembly of TiO₂ nanoparticles (NPs) in multiple layers was selected as a deposition procedure on various substrates. For this, the main prerequisite constitutes the surface modification of both NPs and substrate with, for example, silane coupling agents. A set of functionalized TiO₂ NPs has been produced by reaction with either (3-aminopropyl)triethoxysilane (APTES) or (3-aminopropyl)phosphonic acid (APPA) to functionalize the NP surface with free amino-groups. Then, the complementary functionalized NP set can be obtained from an aliquot of the first one, through the conversion of free surface amino groups to aldehydes by reaction with glutaraldehyde (GA). Several types of TiO₂ NPs differing in size, shape, and specific surface area have been functionalized. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), SEM/ energy-dispersive X-ray spectroscopy (EDS), XPS, Auger electron spectroscopy (AES), and Time-of-Flight (ToF)-SIMS analyses have been carried out to evaluate the degree of functionalization, all the analytical methods employed demonstrating successful functionalization of TiO₂ NP surface with APTES or APPA and GA.     

Reversing Gels and Water Soluble Colloids from Aminosiloxanes

The unique sol/gel behavior of an organic/inorganic hybrid material synthesized from 3-aminopropyl-triethoxysilane (3AS) and tetramethoxysilane (TMOS) is discussed and examined. The addition of H2O to a mixture of a basic (3AS) and an acidic (TMOS) alkoxide leads to rapid gel formation. This wet gel reverses to a sol upon heating which is attributed to the dissolution of siloxane bonds between the surfaces of colloidal particles in the gel. The reversed sol dries to an optically transparent solid which is water soluble. The water solubility and the stability of these colloidal particles are described by their aminopropyl/silanol surface and the electrostatic interactions between them using DLVO theory.     

Preparation and properties of poly(styrene-co-maleic anhydride)/silica hybrid materials by the in situ sol–gel process

Poly(styrene-co-maleic anhydride)/silica hybrid material has been successfully prepared from styrene–maleic anhydride copolymer and tetraethoxysilane (TEOS) in the presence of a coupling agent (3-aminopropyl)triethoxysilane (APTES) by an in situ sol–gel process. It was observed that the gel time of sol–gel solution was dramatically influenced by the amount of APTES. The hybrid material exhibits optical transparency almost as good as both silica gel and the copolymer. The covalent bonds between organic and inorganic phases were introduced by the aminolysis reaction of the amino group with maleic anhydride units of copolymer to form a copolymer bearing trimethoxysilyl groups, which undergo hydrolytic polycondensation with TEOS. The differential scanning calorimetry (DSC) showed that the glass transition temperature of the hybrid materials increases with increasing of SiO₂ composition. Photographs of scanning electron microscopy (SEM) and atomic force microscopy (AFM) inferred that the size of the inorganic particles in the hybrid materials was less than 20 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1607–1613, 1998     

Structure Analysis of PVC Nanocomposites

In this paper poly(vinyl chloride)/clay nanocomposites were prepared by melt intercalation using a single screw extruder. Problems with thermal stability of these nanocomposites during compounding were largely eliminated by pre-treatment of the organoclay with plasticizer (dioctyl phthalate), which created a barrier between polymer and quaternary amine. These nanocomposite materials were analyzed with respect to their morphology. The intercalation, exfoliation, nano-phase dispersion and orientation were investigated using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray diffraction (XRD). Moreover, different types of sample preparation for these techniques were tested as well. It was found that partially intercalated and disordered structure arose in poly (vinyl chloride) composites containing sodium type of montmorillonite, while a fine dispersion of partial to nearly full exfoliation of individual montmorillonite layers in poly (vinyl chloride) matrix was observed when this clay was organically modified. Finally, the influence of different mixing time (in extruder) on nano-phase morphology was surveyed.     

Acidity of montmorillonite pillared by alumina, zirconia and chromia

Acidic properties of Al-, Zr- and Cr- pillared montmorillonites prepared from Jelšovy Potok bentonite (Central Slovakia) have been investigated using temperature-programmed desorption of ammonia. The number of acid sites varied with different interlayer cations from 0.06 to 0.23 mmol g⁻¹. The character of acid sites was similar in the case of Al- and Zr- forms. It is obvious that the chromium analogue contains fewer acid sites, nevertheless, they seem to be stronger compared to Al- and Zr- pillared montmorillonites.     

3-Chloropropyltrialkoxysilanes—Key Intermediates for the Commercial Production of Organofunctionalized Silanes and Polysiloxanes

Silicon and carbon may be looked upon as the two fundamental antipodes with respect to the naturally occurring forms of matter and life on earth: Silicon plays the key role in the “petrification” of inanimate matter, while carbon is the representative element for the “incarnation” of living organisms. If a scientist were to search for a highly efficient method of uniting inorganic and organic matter, he would, at a very early stage of attempting to solve this problem, combine these two natural principles of matter and think of “bireactive” molecules containing a silicon functionality for bonding to inorganic material on the one hand and a carbon functionality for anchoring to an organic counterpart on the other. The title compounds and their derivatives epitomize such molecules: they are wanderers between both (chemical) worlds. Owing to their bifunctionality they are capable of binding to inorganic (especially siliceous) systems as well as to organic polymers. Whether their commercial application concerns the strengthening of polyester resins with glass fibers for use in boatbuilding or the incorporation of silica as a filler in rubber mixtures for the manufacture of wear-resistant tires or even the immobilization of enzymes on glass spheres for carrying out reactions in enzyme reactors—in all cases organofunctionalized silanes guarantee a reliable and permanent union between two otherwise “incompatible” material systems.     

聚乳酸/蒙脱土纳米复合材料的结构和热性能

聚乳酸/蒙脱土纳米复合材料的结构和热性能;聚乳酸;蒙脱土;纳米复合材料;插层     

Molecular motion in nanocomposites of poly(ethylene oxide) and montmorillonite

Motion of chains of poly(ethylene oxide) within the interlayer spacing of 2:1 phyllosilicate/montmorillonite was studied with ¹H and ¹³C NMR spectroscopy. Measurements of the ¹H NMR line widths and relaxation times across a large temperature range were used to determine the effect of bulk thermal transitions on polymer chain motion within the nanocomposites. The results were consistent with previous reports of low apparent activation energies of motion. Details of the frequency and geometry of motion were obtained from a comparison of the ¹³C cross‐polarity/magic‐angle spinning spectra and relaxation times of the nanocomposite with those of the pure polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1678–1685, 2001     

Hybrid RSiO1.5/B2O3 Gels from Modified Silicon Alkoxides and Boric Acid

A new sol-gel route, without any external water addition, for the preparation of hybrid RSiO_1.5/B₂O₃ gels (R = Me, Et, Vi) is reported. The gels are easily synthesized by reacting B(OH)₃ with the liquid silicon alkoxide. The gels have been characterized mainly by FT-IR and ¹¹B MAS NMR spectroscopy. The results show that this new sol-gel process allows the formation of a homogeneous borosilicate gel in which trigonal BO₃ units are incorporated into the siloxane network via B—O—Si bonds.     

DBU的合成及其在羟基酸和伯醇消除反应中的应用

己内酰胺与丙烯腈在乙醇中反应生成Ｎ－（２－氰乙基）己内酰胺接着用ＲａｎｅｙＮｉ－ＫＢＨ＿４在温和条件下还原得到Ｎ－（３－氨基丙基）己内酰胺　再经脱水即得ＤＢＵ３．研究了ＤＢＵ在ω－羟基（烯）酸和伯醇消除反应中的作用。     

Structure and thermal/mechanical properties of poly(l-lactide)-clay blend

Organophilic montmorillonite was obtained by the reaction of montmorillonite (MON) and distearyldimethylammonium chloride (DSAC). The modified clay and poly(l-lactide), (PLLA), were solvent-cast blended using chloroform as cosolvent. The structure and properties of the PLLA-clay blends were investigated. Thermal measurements revealed that cold crystallization took place in the as-cast PLLA, and that the clay served as a nucleating agent. From small and wide-angle x-ray scattering measurements, it was found that silicate layers forming the clay could not be individually well dispersed in the PLLA-clay blends prepared by the solvent-cast method. In other words, the clay existed in the form of tactoids, which consist of several stacked silicate monolayers. However, these tactoids formed a remarkable geometrical structure in the blend films. That is, their surfaces lay almost parallel to the film surface, and were stacked with the insertion of PLLA crystalline lamellae in the thickness direction of the film. During the blend drawing process, fibrillation took place with the formation of plane-like voids developed on the plane parallel to the film surface. Furthermore, delamination of the silicate layers did not occur even under the application of a shearing force. Finally, Young's modulus of the blend increased with the addition of a small amount of the clay. © 1997 John Wiley & Sons, Inc.     

Synthesis and Crystal Structure of a New Ternary Mixed Ligand Complex [Cu（ampym）（bapa）Cl]（ClO4） （ampym = 2-Aminopyrimidine, bapa = Bi（3-aminopropyl）amine）

1 INTRODUCTION The pyrimidine substructure plays a vital role in physiological system. It occurs not only in organisms such as nucleic acids, vitamins and coenzymes[1~3], but also frequently presents in commercially availa- ble drugs such as antibiotics, antiatherosclerotic and antihypertensive agent[4, 5]. Studying the interaction of pyrimidine derivatives and metal ions is important as a means of understanding the role of pyrimidine ring in biological systems. This paper describes the …     

Fluorescence Correlation Spectroscopy Study of Probe Diffusion in Poly(vinyl alcohol) Solutions and Gels

In this study, we demonstrate how the diffusion of probe particles in aqueous poly(vinyl alcohol) (PVA) solutions and gels is affected by: (i) the presence of cross-links, (ii) the cross-link density, (iii) the polymer concentration. We apply fluorescence correlation spectroscopy (FCS) to measure the diffusion time of a rhodamine-based fluorescent particle (TAMRA) and TAMRA-labeled dextran in PVA solutions and gels prepared at various polymer concentrations (1% to 8.6% w/v) and cross-link densities (1/400 to 1/50 cross-link monomers per PVA monomers). The measurements indicate that the probe particles are slowed down with increasing polymer concentration and with increasing cross-link density. Also, FCS can detect differences in the diffusion times measured in “fresh” and “aged” PVA solutions. We find that FCS provides a quantitative measure of network inhomogeneities.     

不同取代位置的萘衍生两亲分子在气/液界面组装膜中的螺旋结构与圆偏振发光

Langmuir-Blodgett(LB)技术可在二维气/液界面上精确地控制分子之间的排列及堆积方式, 构建有序超薄膜及纳米组装体. 同时, 界面这一不对称环境也可有效放大组装体的手性信息, 实现超分子体系中的手性传递和手性放大. 本文研究了萘环取代位置不同的两种手性两亲分子——N,N′-双十八烷基-α-萘-L-氨基-谷氨酸二酰胺(1NLG)和N,N′-双十八烷基-β-萘-L-氨基-谷氨酸二酰胺(2NLG)在气/液界面的铺展及组装行为, 发现同分异构效应影响了两亲分子在界面的排列, 1NLG组装形成了均一的纳米带状结构, 而2NLG则形成了左手螺旋结构, 并且2NLG薄膜表现出圆偏振发光(CPL)性质, 其不对称因子(g_lum)比三维体相组装体(超分子凝胶)大23倍, 表明界面促进了超分子手性的放大.     

Luminescence behavior of inorganic and metalorganic europium(III) dopants incorporated into silica and epoxy-diol ORMOSIL sol-gel hosts

The narrow, intense emission bands of europium (III) make its compounds of interest for various optical source applications. Previous studies have indicated that complexes like tris(4,4,4-trifluoro-1-(2-thieny1)-1,3-butanedionato-O,O)europium(III), Eu(ttfa)₃, have superior fluorescence properties in select media with respect to comparable inorganic salts like EuCl₃. It has been shown that such complexes are readily incorporated into solid-state matrices via the sol-gel process. The present research examines the luminescence behavior of Eu(ttfa)₃ and EuCl₃ doped into a sol-gel-derived epoxy-diol ORMOSIL host, and extends our earlier work involving doped silica and acrylate ORMOSIL gel materials. The present study focuses on the effects of dopant-matrix interactions and seeks to compare the emission behavior of Eu(ttfa)₃ and EuCl₃ in silica and epoxy-diol ORMOSIL gel host materials.