液晶聚合物的单层与Langmuir-Blodgett膜

系统研究了手性液晶聚硅氧烷和光致变色液晶聚硅氧烷两个毓的侧链液晶聚合物在空气/水界面的单层行为和Langmuir-Blodgett(LB)膜沉积特性,对LB膜结构与存在的聚集现象进行了系统的表征,并初步探讨了LB膜中液晶聚合物表现的功能性。     

可溶性聚酰亚胺液晶取向膜的制备与性能

液晶取向膜是液晶显示器中的关键材料,为了制得性能优良的液晶取向膜,我们通过铃木偶联反应制备了3种含有不同末端基团的3,5-二氨基联苯,将制得的3种二胺单体分别与环丁烷四甲酸二酐聚合得到3种新型的聚酰亚胺。 利用核磁氢谱对单体和聚合物的结构进行了表征,测试了聚合物的溶解性、热稳定性以及用作液晶取向膜的性能。 结果表明,所得的聚酰亚胺具有良好的溶解性和热稳定性,经过机械摩擦后,末端带有甲氧基的聚酰亚胺能使液晶分子平行于摩擦方向取向,末端带有苯氧羰基和联苯氧羰基的聚酰亚胺能使液晶分子垂直于摩擦方向取向。 此类可溶性的聚酰亚胺液晶取向膜将简化制备工艺并在柔性显示器件中具有较大的应用价值。     

原位红外光谱法研究电纺聚酰胺酸纳米纤维膜热亚胺化过程

以均苯二酐和二苯醚二胺为原料合成聚酰胺酸溶液,通过静电纺丝法制得聚酰胺酸纳米纤维膜.利用原位红外技术研究亚胺化进程,并以优化的条件制得聚酰亚胺纳米纤维膜.研究结果表明,当升温速率为2℃/min时,在350℃可实现100%亚胺化;升温速率过快,纳米纤维膜的亚胺化程度较低;采用快速-慢速相结合的升温方法,则可以有效地提高亚胺化效率.     

聚酰亚胺LB膜热解制备SiC薄膜的XPS研究

用XPS对沉积在硅基片上的聚酰亚胺LB膜以及由它真空热解制备的SiC薄膜进行了研究 ,并对其形成过程进行了跟踪分析 .XPS结果显示聚酰亚胺LB膜结构均匀 ,质量良好 ;真空热解时 ,约在 6 70℃时LB膜中的C与衬底Si反应形成SiC ;Ar离子溅射深度俄歇谱表明所制备的SiC膜中Si和C浓度成梯度分布 ,说明SiC是由Si和C相互扩散反应形成的     

聚酰亚胺/SiO2杂化膜的制备、表征和气体渗透性能

采用溶胶凝胶法,在以TiO2为过渡层的硅藻土-莫来石陶瓷膜管基底上,制备了组分不同的聚酰亚胺/SiO2杂化膜。聚酰亚胺是利用4,4′-六氟亚异丙基邻苯二甲酸酐、2,4,6-三甲基-1,3-苯二胺和3,5-二氨基苯甲酸在溶液中进行亚胺化完成的。采用FT-IR、TG/DTA、DSC、SEM、BET和气体渗透测定对膜进行了表征和测试。结果表明,聚酰亚胺通过支链上的羧酸基和SiO2相键连织构成了具有规则孔道的空间网状结构,并且随着SiO2含量的增加孔径逐渐减小;杂化膜具有较高的热稳定性和有机无机兼容性;相对于聚酰亚胺膜,杂化膜对H2、CO2和H2O与N2相比较具有较高的分离性,SiO2含量为25(wt)%的杂化膜对H2/N2、CO2/N2和H2O/N2的分离因子分别达到55.9、31.1和42.8。     

聚酰亚胺LB膜研究：Ⅱ.聚酰胺酸N,N—二甲基十八铵盐LB膜的表征 …

聚酰胺酸Ｎ,Ｎ－二甲基十八铵盐ＬＢ膜具有严格排列的周期结构,其亚胺化可以在比聚酰胺酸更为温和的条件下进行。测定了沉积在单晶硅片上的聚酰亚胺涂膜的热分解性能。于真空和高温下聚酰亚胺ＬＢ膜会热解并与基片硅反应而生成规则结构的ＳｉＣ准单晶膜。     

聚酰亚胺LB膜研究 Ⅱ.聚酰胺酸N,N-二甲基十八铵盐LB膜的表征和热分解性能

聚酰胺酸Ｎ,Ｎ－二甲基十八铵盐ＬＢ膜具有严格排列的周期结构,其亚胺化可以在比聚酰胺酸更为温和的条件下进行。测定了沉积在单晶硅片上的聚酰亚胺涂膜的热分解性能。于真空和高温下聚酰亚胺ＬＢ膜会热解并与基片硅反应而生成规则结构的ＳｉＣ准单晶膜。     

耐超高温双酮酐型聚酰亚胺的合成及性能

以4,4'-对苯二甲酰二邻苯二甲酸酐(TDPA)为芳二酐单体,对苯二胺(PPD)为芳二胺单体,经低温溶液缩聚制得成膜性能优良的高相对分子质量聚酰胺酸(PAA),再经过热亚胺化制备双酮酐型聚酰亚胺(PI)薄膜。 采用傅里叶变换红外光谱仪(FT-IR)、广角X射线衍射(WAXD)、差示扫描量热仪(DSC)、动态热机械分析仪(DMA)、热重分析仪(TGA)、紫外-可见分光光度计(UV-Vis)及力学性能等技术手段表征了聚酰亚胺膜的结构和性能,考察了不同亚胺化温度对合成的双酮酐型聚酰亚胺膜性能的影响。 结果表明,经程序升温至320 ℃能使PAA热亚胺化基本趋于完成。 PI薄膜为部分有序聚集态结构,玻璃化转变温度(T_g)为298 ℃,具有优异的热性能,热失重温度(T_5%)为523 ℃。 拉伸强度达到130 MPa,弹性模量为5.77 GPa。 PI薄膜紫外光透过截止波长为375 nm,在可见光区具有良好的透光性能及耐溶剂性能。     

聚酰亚胺光控取向膜的研究现状

用线性偏振紫外光照射聚酰亚胺膜可以诱导液晶取向。本文对四种聚酰亚胺光控取向膜进行了详细的概述，并简述了这种光控取向膜的机理及未来应用。     

含液晶基团的冠醚LB膜研究

合成了含有联苯介晶基团的长链冠醚,并首次制成含液晶基团的冠醚LB膜,由LB膜的荧光光谱研究发现,与其单体在CHCl_3稀溶液中的荧光光谱相比,LB膜的荧光光谱向长波方向移动,表明分子均以缔结状态存在,XRD结果表明,LB膜具有良好的有序结构,单分子膜厚2.6nm。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.