聚酯型脂肪族和芳香族聚氨酯硬段结晶特性对比

本文利用DSC、IR、WAXD、PLM和SALS等实验手段,探讨了具有相同软段的聚酯型脂肪族和芳香族聚氨酯硬段结晶特性的差异,发现脂肪族聚氨酯的相分离速率极快,氢键主要在硬段间形成,因而对硬段的结晶过程影响不大;而芳香族聚氨酯的相分离速率较慢,软硬段间又能形成氢键,因而对硬段的结晶起了阻碍作用。     

任意矩阵伸缩的正交小波包

1 引言 Coifman和Meyer引入L~2(R)中正交小波包,可以用张量积形式构造L~2(R~2)上的二维正交小波包;Chui和Li研究单变量非正交小波包和对偶小波包;Shen给出矩阵伸缩为2I时L~2(R~s)上非张量积小波包的构造算法;程正兴给出矩阵小波包的构     

Photochromism of new unsymmetrical diarylethenes with a quinoline moiety

Three unsymmetrical diarylethenes with a 6‐membered quinoline moiety were synthesized to investigate the effects of the substituents on their photochromism, and fluorescence, and the structure of one diarylethene was determined by single crystal X‐ray diffraction analysis. Quinoline was connected directly to the central perfluorocyclopentene ring as an aryl moiety and available to participate in photoisomerization reaction in solution, amorphous films, and crystalline phase. These diarylethenes exhibited good photochromism with excellent thermal stability and obvious fatigue resistance. The electron‐donating methoxy group could enhance the absorption maxima of closed‐ring isomers and the quantum yields of cyclization and cycloreversion, but the electron‐withdrawing trifluoromethyl had an opposite effect. In addition, they functioned as notable fluorescence switches in both solution and polymethylmethacrylate films, and the trifluoromethyl group and the methoxy group both increased the emission intensity. The results revealed that the quinoline moiety and substituents played a vital role in the process of photoisomerization reactions for these diarylethenes.     

正交小波包的构造

本文给出尺度因子ａ＝４时正交小波包的构造，推广了［２，４］引入的正交小波包，并给出相应的分解与再构造算法．本文引入的正交小波包具有保持信号ｆ∈Ｌ^２的线性相位，也讨论了尺度因子ａ＝ｋ（ｋ∈Ｚ，ｋ≥２）正交小波的构造     

Photochromism of new unsymmetrical isomeric diarylethenes bearing a methoxyl group

Three new unsymmetrical isomeric diarylethenes having a methoxyl substituent at ortho‐, meta‐, and para‐position of the terminal benzene ring, namely 1‐(2,5‐dimethyl‐3‐thienyl)‐2‐[2‐methyl‐5‐(2‐methoxylphenyl)‐3‐thienyl]perfluorocyclopentene ( 1o ), 1‐(2,5‐dimethyl‐3‐thienyl)‐2‐[2‐methyl‐5‐(3‐methoxylphenyl)‐3‐thienyl]perfluorocyclopentene ( 2o ), and 1‐(2,5‐dimethyl‐3‐ thienyl)‐2‐[2‐methyl‐5‐(4‐methoxylphenyl)‐3‐thienyl]perfluorocyclopentene ( 3o ), have been synthesized. The substituent position effect of methoxyl group on their properties, including photochromism and fluorescence both in hexane solution and in PMMA film, and their electrochemical properties, were investigated in detail. These diarylethenes showed good photochromism both in solution and in PMMA film. For the same photochromic diarylethene backbone, the electron‐ donating methoxyl substituent can effectively depress the cyclization quantum yields and increase the cycloreversion quantum yields compared to those of diarylethenes bearing chlorine atoms reported previously. Diarylethenes 1o – 3o showed clear fluorescent switches by photoirradiation both in hexane and in PMMA film. In addition, cyclic voltammetry tests showed that the electron‐donating methoxyl group at different position on the terminal benzene ring had a significant effect on the electrochemical properties of these isomeric diarylethenes. Copyright © 2009 John Wiley & Sons, Ltd.     

1,8-亚乙基萘在三氟化硼乙醚-聚乙二醇中的电化学聚合

在三氟化硼乙醚(BFEE)-聚乙二醇(分子量400,PEG400)混合电解质溶液中,1,8-亚乙基萘直接阳极氧化聚合可以获得自支撑聚(1,8-亚乙基萘)膜.单体在三氟化硼乙醚+10%PEG400中的起始氧化电位为0.95 Vversus SCE,远低于单体在0.1 mol.L-1四氟化硼四丁基胺-乙腈溶液中的起始氧化电位(1.38 VversusSCE).同时PEG400的加入可以有效改善单体在三氟化硼乙醚中的溶解性.UV-Vis,FTIR和1H-NMR确定了1,8-亚乙基萘在4,5位聚合,荧光光谱表明固态及可溶聚(1,8-亚乙基萘)膜是蓝色发光材料.     

A silver(I)–rhodium(I) cooperative catalysis in the reaction of N′-(2-alkynylbenzylidene)hydrazide with 2-vinyloxirane

A novel and efficient route to H-pyrazolo[5,1-a]isoquinoline-1-carbaldehydes via a tandem reaction of N′-(2-alkynylbenzylidene)hydrazide with 2-vinyloxirane is described. The reaction proceeds through a silver(I)–rhodium(I) cooperative catalysis.     

Synthesis, structure and fluorescence of a novel diarylethene

The photochromic diarylethene, 1,2-bis(2-methyl-5-(2-(1,3-dithiolpentane))-thien-3-yl)perfluorocyclopentene (BMDTP), has been synthesized in high yield and its structure was determined by X-ray crystallographic analysis. The compound undergoes a photochromic reaction both in solution and in the single crystalline phase. In addition, its fluorescence property in solution is discussed.     

Synthesis and the effect of alkyl chain length on optoelectronic properties of diarylethene derivatives

Photochromic symmetrical diarylethene derivatives 1a-6a bearing different long alkyl chains at 2-position of thiophene rings have been synthesized and their structures have been determined by single-crystal X-ray diffraction analysis. The effect of alkyl chain length on their optoelectronic properties, such as photochromism in solution as well as in the crystalline phase and electrochemical performance was investigated in detail. These diarylethenes have showed good photochromic behavior both in solution and in the single crystalline phase. Introduction of the long alkyl chains at 2-position of bis(5-formyl-3-thienyl)perfluorocyclopentene increased the absorption coefficients of both open- and closed-ring isomers and induced bathochromic shifts of the maximal wavelength absorption of the closed-ring isomers. The long alkyl chains can also decrease the cyclization/cycloreversion quantum yields and the oxidation potentials. The cyclic voltammetry indicated that the band gap of these diarylethene derivatives was significantly affected by the alkyl chain length.     

Synthesis of 2-(polyfluoroaryl)benzofurans via a copper(I)-catalyzed reaction of 2-(2,2-dibromovinyl)phenol with polyfluoroarene

A novel and efficient route for the synthesis of 2-(polyfluoroaryl)benzofurans via a copper(I)-catalyzed tandem reaction of 2-(2,2-dibromovinyl)phenol with polyfluoroarene is reported. The corresponding products are generated in good yields. During the reaction process, a copper-catalyzed intramolecular C-O bond formation and a C-H activation are involved.