Siloxane-Based Nanobuilding Blocks by Reaction Between Silanediol and Trifunctional Silicon Alkoxides

The preparation of nanostructured organic-inorganic materials by assembling of nanobuilding blocks allows controlling the extent of phase interaction, which in its turn governs structure-properties relationships. We present here the synthesis of siloxane-based nanobuilding blocks prepared by reacting diphenylsilanediol with vinyltriethoxysilane and triethoxysilane. The reaction products were obtained by non-hydrolytic condensation between silanediol and ethoxide groups in inert atmosphere, in the presence of pyridine, triethylamine or butyl lithium. Different synthetic conditions were examined by means of ATR-FTIR and NMR spectroscopies, showing the formation of siloxane bonds. In the case of triethoxysilane the reaction carried out in the presence of pyridine leads to Si–H bond preservation in the final product. Air stable products with improved Si–O–Si hydrolytic stability can be obtained by removal of the base after the reaction completion. The condensation products can be described as a mixture of siloxane rings involving difunctional and trifunctional silicon units.     

Lamellar Organo-Bridged Silicones

The acid-hydrolysis of an organo-bridged bisdiethoxysilylated molecular precursor bearing urea groups, (EtO)₂MeSi(CH₂)₃NHCONH(CH₂)₁₂NHCONH(CH₂)₃SiMe(OEt)₂, has been performed in pure aqueous medium. Scanning electron microscopy (SEM) analysis of the resulting insoluble solid revealed plate-like forms with a lamellar structure as determined by powder X-ray diffraction (PXRD) studies with a sharp peak at 28.5 Å. The solid state ²⁹Si MAS-NMR spectrum of this bridged siloxane hybrid is consistent with a moderately condensed material with complete preservation of the Si–C bonds throughout the hybrid network. In comparison, the classical sol–gel hydrolysis-condensation of the molecular precursor in ethanol with stoichiometric amount of water and fluoride anion as catalyst produced an amorphous featureless solid.     

Compositional Profiles in Silica-Based Sol-Gel Films Doped with Erbium and Silver, by RBS and ERDA

Photosensitive organic-titania hybrid materials have been prepared from metal alkoxides and various organic ester compounds with double bonds. The refractive index of the film increases with the decrease of the concentration of the organic ester compound, and the highest refractive index of 1.62 is obtained when 2-hydroxymethyl acrylate (HOA) is used as the organic ester and the molar ratio of HOA to Ti is 0.5. The material with the highest refractive index is exposed to femtosecond pulse using the multi-beam laser interference technique. After laser irradiation, the irradiated parts of the material are photopolymerized and periodic structures can be obtained by development of the unirradiated parts. In the case of laser irradiation of 120 J total energy for 5 min, the periodic structure obtained corresponds to 2D photonic crystal structure which is composed of two parts; the material with the highest refractive index and the air.     

Adsorption Isotherm of Water Vapor and Its Large Hysteresis on Highly Ordered Mesoporous Silica

The first and second adsorption–desorption isotherms of water vapor on a new mesoporous material derived from kanemite have been measured. The isotherms show unusual type V isotherms and large hysteresis. The type V isotherms, which have never been observed for the other adsorbates, suggest that the mesoporous material has a hydrophobic surface, although the hydrophobicity decreased after treatment with water vapor because of rehydration of the surface. The significantly large hysteresis could be explained by the difference in contact angle between adsorption and desorption.     

三维有序大孔杂化材料SiW11O39^8——SiO2和γ—SiW10O36^8——SiO2的制备与表征

通过溶胶 -凝胶和聚苯乙烯模板等方法制备了含缺位 Keggin阴离子 Si W1 1 O8- 3 9和 γ-Si W1 0 O8- 3 6的三维有序大孔杂化氧化硅复合材料 ,并通过紫外漫反射光谱 ( UV/ DRS)、傅里叶变换红外光谱 ( FTIR)、固体核磁共振波谱 ( MAS NMR)等手段对其结构进行了表征 .结果表明 ,杂化材料中的 Keggin阴离子仍保留其基本骨架结构 ,但其与氧化硅基体之间存在化学作用 .杂化材料的孔道结构用扫描和透射电子显微镜 ( SEM和TEM)进行表征 ,其平均孔径为 ( 335± 5 0 ) nm.对杂化材料孔壁的微孔性通过氮气吸附进行了测定 .此类材料对水溶液中羟基丁二酸的降解反应具有活性 ,光催化过程中未发现 Keggin阴离子自载体中脱落的现象 .     

Preparation of mesoporous aluminophosphate using poly(amido amine) as template

Mesoporous aluminophosphate was prepared by using G4.0 poly(amido amine)dendrimer as a template and characterized by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ adsorption/desorption methods. Results show that the title compound exhibits a typical mesoporous structure with the average pore size from 5 to 8 nm. The formation mechanism of the nanoporous structure using dendrimer as a template was also discussed. __________ Translated from Journal of Fujian Normal University (Natural Science Edition), 2007, 23(2): 67–70 [译自: 福建师范大学学报 (自然科学版)]     

Optical Nonlinearity of Hybrid and Nanocomposite Materials Prepared by the Sol-Gel Method

In this paper the nonlinear refractive index, optical limiting effect, photoinduced and electroinduced second harmonic generation of dye-doped hybrid and nanoparticle-doped composite materials prepared by the sol-gel process have been reported. The origin of these nonlinear optical effects has been discussed.     

The Electrochemical Behavior of Keggin Polyoxometalate Modified by Tricyclic,Aromatic Entity

The inorganic‐organic hybrid polyoxometalates (POMs), (pbpy)₄H[PMo₁₂O₄₀(VO)] ( 1 ) and (pbpy)₄H₄[SiMo₁₂O₄₀] ( 2 ) (pbpy=5‐phenyl‐2‐(4‐pyridinyl)pyridine), have been synthesized and were, respectively, used as a solid bulkmodifier to fabricate a three‐dimensional bulk‐modified carbon paste electrode (CPE) by direct mixing. The electrochemical behavior and electrocatalysis of 1 and 2 modified CPE ( 1 ‐CPE and 2 ‐CPE) have been studied in detail. Both 1 ‐CPE and 2 ‐CPE show remarkable stability that can be ascribed to the doped organic conjugated pbpy, which is very important for practical applications in electrode modification.     

Infrared Evidence for Hoffman Reaction During Calcination of Surfactant-Templated Silica Films and Analysis of the Resulting Surface Sites

Fourier Transform Infrared transmission spectroscopy is used to characterize surfactant-templated silica films on glass. The calcination process is followed in situ and evidence for the removal of the surfactant along the Hoffman reaction is given. Once calcined, the surface of the pores of the mesoporous films is proven by deuteration experiment to be hydroxylated. Bands are attributed to isolated and hydrogen-bonded silanols. Silylation reaction with hexamethyldisilazane only occurs with isolated silanol groups.