Effects of annealing treatment on the properties of MEH-PPV/titania hybrids prepared via in situ sol-gel reaction

A uniform poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV)/titania hybrid film was successfully prepared by an in situ sol-gel reaction of titanium isopropoxide (TIP) in the presence of MEH-PPV/2-chlorophenol solution. The annealing treatment increased the conversion of TIP to titania as determined from evidence of the formation of Ti-O-Ti bonds in the Fourier transform infrared (FTIR) spectrum. Scanning electronic microscope (SEM) photographs showed that the morphology and distribution of titania in the hybrid film were strongly related to the amount of water in the in situ sol-gel reaction. The thermal stability of MEH-PPV/titania hybrids was enhanced by the annealing treatment. Small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) analyses indicated that annealing treatment promoted the ordered aggregation of the MEH-PPV chains and crystallization of titania to a certain extent. The blue shift in Ultraviolet-visible (UV-vis) absorption of pure MEH-PPV after annealing was ascribed to the small extent of decomposition and coil conformation which occurred at high temperature. A more-obvious blue shift for the hybrids was observed, which resulted from irregular aggregation and coil conformation of the MEH-PPV chains induced by heterogeneous point, TIP (titania). The red shift in the photoluminescent (PL) emission for pure MEH-PPV resulted from a certain extent of ordered aggregation after annealing. However, only a slight red shift in the PL emission peak for the hybrids was found due to the hindrance of ordered aggregation of MEH-PPV chains in the presence of TIP (titania).     

Silica-Based and Transition Metal-Based Inorganic-Organic Hybrid Materials—A Comparison

Organically substituted metal alkoxides can be prepared by reaction of the parent alkoxides with complexing organic compounds. The chemical and structural consequences of such substitutions are discussed in this article. Examples are given showing how functional organic moieties, such as polymerizable groups, can be incorporated into sol-gel materials via the complexing ligands. Major structural differences between silica-based and metal-based hybrid materials originate from the different charge/coordination number ratios of silicon and most metals. This results in a high tendency for the molecular building blocks to aggregate. In many cases, metal oxide clusters are formed which are capped by the organic ligands. Such surface-modified clusters are themselves very valuable condensed matter units for materials syntheses.     

钙钛矿型复合氧化物Ca_xSr_（1－x）TiO_3催化剂上的甲烷氧化偶联反应

在固定床反应器上，评价了不同温度下钙钛矿型复合氧化物ＳｒＴｉＯ３和ＣａＴｉＯ３的组成变化对甲烷氧化偶联反应的影响．同时，利用ＸＰＳ和ＣＯ２－ＴＰＤ对催化剂的结构及其氧物种的反应特性进行了表征．结果表明：ＳｒＴｉＯ３和少量Ｃａ掺杂的ＣａｘＳｒｌ－ｘＴｉＯ３有利于在较低温度（９２３Ｋ）下催化反应的活性和选择性，而ＣａＴｉＯ３体系则在高温（１０７３Ｋ）下表现出较好的活性和选择性．钙钛矿型复合氧化物ＳｒＴｉＯ３和ＣａＴｉＯ３组成变化对不同温度下反应活性的影响与ＣＯ２－ＴＰＤ的脱附谱图有很好的平行关系．     

Synthesis, spectroscopic studies and crystal structure of a polyoxoanion cluster incorporating para-bromophenylimido ligand, (Bu4N)2[Mo6O18(NC6H4Br-p)]

An organic-inorganic hybrid compound, (Bu₄N)₂[Mo₆O₁₈(NAr)] (Ar = p-BrC₆H₄) has been synthesized via the DCC dehydrating protocol of the reaction of [α-Mo₈O₂₆]⁴⁻ with 4-bromoaniline hydrochloride in anhydrous acetonitrile, which has been characterized by UV-Vis spectra, ¹H NMR and single crystal X-ray diffraction study. By comparing the UV-Vis spectra, which were used to monitor the reaction, the optimum preparative condition for this compound was also determined. This compound crystallizes in the monoclinic space group P2₁/n, which is featured in a terminal para-bromophenylimido group linked to an Mo atom of a hexamolybdate cluster by a Mo-N triply bond. In addition, there are π-π dimerization of the neighboring cluster anions though the parallel aromatic rings in their crystals.     

Sol–gel preparation and properties of hydroxypropylcellulose–titania hybrid thin films

Hydroxypropylcellulose (HPC)–titania hybrid thin films were prepared by sol–gel method where titanium tetraisopropoxide Ti(OC₃H₇ ⁱ )₄ was hydrolyzed under acidic conditions in the presence of HPC, followed by dip-coating and drying at 120 °C for 24 h. The viscosity average molecular weight of HPC was 55,000–70,000 or 110,000–150,000, and the TiO₂/(HPC + TiO₂) mass ratio ranged from 0 to 1, which was calculated on the assumption that all Ti(OC₃H₇ ⁱ )₄ is converted into TiO₂. The films were 0.35–1.0 μm thick, transparent in visible region and opaque in ultraviolet (UV) region, where the optical absorption coefficient in UV region increased with increasing titania content. The refractive index increased with increasing titania content, ranging from 1.6 to 1.8 for the hybrid thin films. The pencil hardness increased from 6B to 5H, the durability in hot water significantly increased and the contact angle of water on films increased from 35° to 89° with increasing titania content. Crack-free films could be deposited on organic polymer substrates irrespective of titania or HPC contents, where cracking did not occur at higher HPC contents even when the substrate was bent.     

Comparison between capillary electrophoresis and ion-chromatography for analysis of inorganic anions

Separation and detection of some selected inorganic anions with capillary electrophoresis are shown. The anions are separated in microbore capillaries (25 m* 0.2 m) and detected with a UV-detector. Results are compared with the method of ion exchange chromatography. In consideration of the most important physical and chemical parameters an easy kind of computer simulation for such electropherograms was developed.To get optimal results of separation and UV-detection in capillary electrophoresis some parameters of the device HPE 100, i.e. loading time in the electrokinetic sample injection mode and the running voltage are varied. The behaviour of absorption in the UV region of the chosen anions as well as the influence of pH values in retention behaviour are investigated. There is a simple way to calculate the electrophoretic mobilities from known retention times. Approximate limits of detection for all anions and for each technique are given.     

溶胶-凝胶法合成纳米铬酸锶镧的工艺研究

以硝酸镧、硝酸铬、硝酸锶为原料，乙二醇为分散剂，柠檬酸为胶溶剂，用溶胶-凝胶法合成纳米级的铬酸锶镧粉体。利用TG，DSC，XRD分析研究了粉料的晶化过程。利用HREM分析了煅烧温度、含锶量对粉料粒径的影响。研究表明，获得纳米晶的最佳烧结温度在800℃。随着锶掺杂量的增加，粉料的粒径逐渐变小。     

Sugar-anionic clay composite materials: intercalation of pentoses in layered double hydroxide

The intercalation of non-ionized guest pentoses (ribose and 2-deoxyribose) into the Mg-Al and Zn-Al layered double hydroxides (LDHs) was carried out at 298 K by the calcination-rehydration reaction using the Mg-Al and Zn-Al oxide precursors calcined at 773 K. The resulting solid products reconstructed the LDH structure with incorporating pentoses, and the maximum amount of ribose intercalated by the Mg-Al oxide precursor was approximately 20 times that by the Zn-Al oxide precursor. The ribose/Mg-Al LDH was observed to have the expanded LDH structure with a broad (003) spacing of 0.85 nm. As the thickness of the LDH hydroxide basal layer is 0.48 nm, the interlayer distance of the ribose/Mg-Al LDH is 0.37 nm. This value corresponds to molecular size of ribose in thickness (0.36 nm), supporting that ribose is horizontally oriented in the interlayer space of LDH. The maximum amount of ribose intercalated by the Mg-Al oxide precursor was approximately 5 times that of 2-deoxyribose. Ribose is substituted only by the hydroxyl group at C-2 position for 2-deoxyribose. Therefore, the number of hydroxyl group of sugar is essentially important for the intercalation of sugar molecule into the LDH, suggesting that the intercalation behavior of sugar for the LDH was greatly influenced by hydrogen bond between hydroxyl group of the intercalated pentose and the LDH hydroxide basal layers.     

SYNTHESIS OF MESOPOROUS POLY(STYRENE-co-MALEIC ANHYDRIDE)/SILICA HYBRID MATERIALS VIA A NONSURFACTANT-TEMPLATED SOL-GEL PROCESS*

Mesoporous poly (styrene-co-maleic anhydride)/silica hybrid materials have been prepared. The synthesis wasachieved by the HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and styrene-maleic anhydride copolymerin the presence of 3-aminopropyl triethoxysilane (APTES) as a coupling agent and citric acid as a nonsurfactant template orpore-forming agent, followed by ethanol extraction. Characterization results from nitrogen sorption isotherms and powder X-ray diffraction indicate that polymer-modified mesoporous materials with large specific surface areas (e.g. 900 m~2/g) andpore volumes (e.g. 0.6 cm~3/g) could be prepared. As the citric acid concentration is increased, the specific surface areas, porevolumes and pore diameters of the hybrid materials increase.     

有机/无机杂化材料担载季铵盐催化剂的制备及其在相转移催化反应中的应用

利用溶胶-凝胶(S0l-gel)技术制备了新型的有机／无机杂化材料担载的季铵盐催化剂。优化了制备方法、反应条件等多种因素；考察了其作为相转移催化剂在1-溴代正庚烷与碘化钾的亲核取代反应中的应用，转化率最高可达到95％。