Studies on Ring—Opening Polymerization of Chloromethyl Thiirane with Rare Earth Catalysts and Functional Resins Synthesized therewith

Studies on ring-opening polymerization of chloromethyl thiirane with rare earth catalysts and functional resins synthesized therewith were reviewed.     

稀土化合物催化内酯开环聚合（Ⅲ）──氯化钕－环氧化合物体系催化ε

稀土化合物催化内酯开环聚合（Ⅲ）──氯化钕－环氧化合物体系催化ε－己内酯本体聚合申有青，沈之荃，沈建良，张富尧，张一烽（浙江大学高分子科学与工程学系，杭州，３１００２７）关键词氯化钕，环氧化合物，ε－己内酯，本体聚合聚己内酯（ＰＣＬ）和聚丙交酯（ＰＬ...     

Highly Enantioselective Phenylacetylene Addition to Benzaldehyde Catalyzed by Chiral Tridentate Ligand

Development of new or improved methods for the asymmetric preparation of chiral propargylic alcohols has gained considerable significance during the past years because they are useful building blocks for the synthesis of many biologically active compounds and natural products.[1] A series of chiral tridentate ligands were conveniently synthesized from amino acids with good yields (Scheme 1).[2] A preliminary study of the enantioselective alkynylation of benzaldehyde catalyzed by this chiral tridentate ligand was carried out and up to 83% ee of chiral propargyl alcohols was obtained (Table 1 ). A further investigation of the tridentate ligand is currently underway.     

A novel composite chitosan membrane for the separation of alcohol-water mixtures

A novel alcohol dehydration membrane with a three layer structure has been prepared. The top layer is a thin dense film of chitosan (CS), and the support layer is made of microporous polyacrylonitrile (PAN). Between the dense and microporous layer, there is an intermolecular cross-linking layer. This novel composite membrane has a high separation factor of more than 8000 and a good permeation rate of 0.26 kg/m² h for the pervaporation of 90 wt% ethanol aqueous solution at 60°C, 0.8 kg/m² h flux for a n-PrOH/water system and around 1 kg/m² h flux for an i-PrOH/water system using 80 wt% alcohol concentration at 60°C. The separation factor for both cases is more than 10⁵. The separation performance varies with feed composition, operating temperature and conditions of membrane preparation. The results show that the separation factor and flux of this membrane increase with raising the operating temperature. At the same time, the crosslinking layer improves durability of the composite membrane, and the pervaporation performance can be adjusted by changing the structure of the cross-linking layer. The cross section of the composite membrane has been examined by SEM.     

A simple, rapid, and efficient oxidation of oximes to ketones and aldehydes with manganese dioxide catalyzed by kieselguhr under solvent-free conditions

A simple, rapid, and efficient oxidation of oximes to the corresponding ketones and aldehydes with manganese dioxide catalyzed by kieselguhr under solvent-free conditions at room temperature in the yields between 82 and 98 is described. It seems that kieselguhr in the present procedure can highly expedite the reaction rate. By comparing to other methods described previously, the main advantages of this oxidation are that the oxidations are more efficient, the reaction conditions are milder, the reaction times are shorter, and the work-up is easier. Furthermore, the amount of manganese dioxide used in this oxidation is largely decreased.     

Ring-opening polymerization of macrocyclic aryl ether ketone oligomers containing the 1,2-dibenzoylbenzene moiety

Facile ring-opening polymerization of cyclic aryl ether oligomers containing the 1,2-dibenzoylbenzene moiety to form high molecular weight linear polymers in the presence of a nucleophilic initiator is described. The polymerization can be initiated in the melt in the presence of a nucleophilic initiator such as potassium carbonate, cesium fluoride, and alkali phenoxides. Various alkali phenoxides were investigated as potential nucleophilic initiators. The polymerization reaction rate in the melt increases in the order of K⁺ > Na⁺ > Cs⁺, and in the order of ⁻OPhPhO⁻ > PhO⁻ > PhOPhO⁻ > PhPhO⁻. However, the polymerization in an aprotic dipolar solvent is faster in the presence of cesium phenoxide than in the presence of potassium phenoxide. Polymerization of the cyclic oligomers in solution demonstrates that the ring-opening polymerization proceeds via a chain-growth mechanism and involves a transetherification reaction between linear and cyclic aryl ether oligomers. The ring-chain equilibrium is much more favorable towards linear polymers. Since little or no ring strain exists in the cyclic system, the transetherification reactions are indiscriminate with regards to cyclic or linear chains and the interchain equilibration is also a facile process during polymerization. This intermolecular transetherification has been demonstrated by using low molecular weight aryl ethers to control the molecular weight of the polymer formed via ring-opening polymerization. © 1996 John Wiley & Sons, Inc.     

石墨和纳米碳中缺陷和电子密度随温度的变化

测量了石墨和纳米碳在不同温度下的正电子寿命谱,研究了石墨和纳米碳中缺陷和电子密度随温度的变化.结果表明,纳米碳中缺陷的开空间和缺陷浓度分别大于和高于石墨晶体;纳米碳的平均自由电子密度低于石墨晶体.当温度从25K升至295K时,石墨和纳米碳中的平均自由电子密度随温度的升高而下降:石墨晶体中的自由电子密度随温度的升高变化较小;纳米碳的自由电子密度随温度的升高变化较大.随着温度的升高,石墨和纳米碳中的热空位数量增多,而且这些空位可迁移至微孔洞的内表面使微孔洞的开空间增大.     

一种在弱酸性介质中有电化学发光性能的鲁米诺衍生物

报道了一种鲁米诺的衍生物-3-(1-乙酰丙酮偶氮)苯二甲酰肼在酸性介质中的电化学发光行为,该化合物与鲁米诺类似,发生两步电化学氧化反应,但其氧化电位较鲁米诺低约0.5V,在氧化铟锡玻璃电极上具有良好的电化学发光性能,有效地避免了氧化铟锡玻璃电极本身的发光干扰.不仅在碱性介质中具有较高的电化学发光效率,而且在酸性介质中也产生较稳定的电化学发光,在1.0×10-6mol/L以上浓度,电化学发光强度与浓度有良好的线性关系.     

5-芳氧甲基-2-噁唑烷酮的合成及表征

环氧氯丙烷;氯甲基噁唑烷酮;合成;芳氧甲基噁唑烷酮     

基于碳纳米管修饰电极的胆碱电化学发光生物传感器研制

在碳纳米管(CNTs)和K3Fe(CN)6修饰的铂电极上吸附固定胆碱氧化酶,以鲁米诺为发光试剂,研制了胆碱电化学发光(ECL)生物传感器.CNTs可有效提高电极表面的电荷传输能力、提高电极表面的生物相容性和对酶分子的固载能力;K3Fe(CN)6对酶活性具有激活作用,同时对H2O2增敏的鲁米诺ECL有增强作用,均有利于提...