二氟亚甲氧基噻二唑类弯曲形液晶合成与性能研究

弯曲形液晶以其独特的光电性能倍受关注.但目前所报道的弯曲形液晶化合物因其向列相温度范围较窄,相转化温度高,不利于基础与应用研究,发展缓慢.以2,5-二取代-1,3,4-噻二唑为弯曲中心,二氟亚甲氧基(CF2O)为桥键,直链烷基(n=5~10,12)为末端链基,设计合成了一系列新型弯曲形液晶化合物.所有目标化合物通过IR、1H NMR、13C NMR、9F NMR进行结构表征,并通过差热扫描仪(DSC)和偏光显微镜(POM)对液晶相态进行测定.实验结果表明:所有目标化合物分子,都能呈现较宽的向列相态,最宽达92.74℃(化合物6a);较之结构相当的噁二唑类弯曲液晶化合物,其熔点稍高,液晶相态的温度范围更宽.为进一步设计合成新型宽温向列相弯曲型液晶提供了素材和理论依据.     

2,5-二取代-1,3,4-噁二唑不对称弯曲形液晶合成与性能研究

以2,5-二取代-1,3,4-噁二唑为中心核,酯基(COO)为桥键,烷基(n=5~9)为末端基团,在单侧苯环侧位上引入氟原子,设计合成了两个系列新型不对称弯曲形液晶化合物9a~9e和10a~10e;并通过IR,1H NMR,13C NMR,19F NMR和MS对其结构进行鉴定,经差热扫描仪(DSC)和偏光显微镜(POM)测定其液晶相态.结果表明:所有目标化合物的分子结构正确,都呈现向列相态,向列相态温度范围最宽达78℃;侧位单氟苯环结构化合物9a~9e的向列相态温度范围没有二氟苯环结构10a~10e的宽,并且化合物9a~9e都呈现奇偶效应.     

亚甲氧基桥键弯曲型液晶合成与性能研究

以2,5-二(4-羟基苯基)-1,3,4-噁二唑为中心基团,亚甲氧基(CH2O)为桥键,烷基(m=3,5,6,7,8,9,10)为末端基团合成了一系列新型弯曲型液晶化合物.通过IR,1H NMR,13C NMR和MS对其结构进行鉴定,经差热扫描仪(DSC)和偏光显微镜(POM)测定其液晶相态.结果表明,目标化合物6a~6g的分子结构正确,其熔点较结构相当的酯类液晶化合物低,除6c外,其它化合物熔点均在100℃以下,都呈现液晶相态,且化合物6d~6g的相态温度范围较宽,并呈现奇偶效应.     

侧基含羟基的主链偶氮苯液晶共聚酯的合成及其光响应行为

以4,4’-双(6-羟基己氧基)联苯(BHHBP)、4,4’-双(6-羟基己氧基)偶氮苯(BHHAB)为液晶基元,利用苹果酸二乙酯(DM)和苯基丁二酸(PSA)采用无规共聚,合成了侧基含羟基的偶氮苯液晶共聚酯(Az-LCP).先在液晶态下拉伸取向,然后用六亚甲基二异氰酸酯(HDI)交联制备单畴取向偶氮苯液晶交联网络.通过核磁共振氢谱(1H-NMR)、凝胶渗透色谱(GPC)测试,对合成的Az-LCP进行结构表征,通过示差扫描量热分析(DSC)、X射线衍射(XRD)、偏光光学显微镜(POM)等对其液晶相变行为进行表征,研究了偶氮苯含量、交联密度、薄膜厚度对其光致弯曲行为的影响.结果表明,偶氮苯含量10%,交联12 h的Az-LCP1具有最佳的光致弯曲回复行为.     

星型液晶的合成、相行为与应用研究

通过SiCl4的Si-Cl键与偶氮苯类液晶基元末端OH的有效联接，合成了三种新的 星型液晶，利用红外光谱（IR）、核磁共振（^1H NMR)对其分子结构进行了鉴定， 利用偏光显微镜（POM）和示差扫描量热法（DSC）对 其液晶相行为进行了表征， 并对其在毛细管气相色谱分析中的应用进行了初步探讨。     

基于原子转移自由基聚合技术的偶氮苯星形液晶聚合物的合成与表征

利用原子转移自由基聚合(ATRP)技术合成了含不同端基取代基的偶氮苯三臂星形侧链液晶聚合物. 均苯三酚与2-溴异丁酰溴通过酯化反应制备三官能团引发剂, 引发偶氮苯单体6-[4-(4-甲氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(MMAzo)或6-[4-(4-乙氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(EMAzo)的ATRP反应. 利用核磁共振氢谱(¹H NMR)、凝胶色谱(GPC)、差示扫描量热法(DSC)和偏光显微镜(POM)等手段对星形聚合物进行表征. 星形聚合物的液晶性与相应均聚物相似, 但偶氮苯端基取代基的不同导致星形聚合物的液晶性差别显著. 在紫外/可见光照射下星形聚合物呈现明显的异构化转变.     

端基含己氧基偶氮苯基元的一代光致变色液晶碳硅烷树状物的光响应行为研究

研究了端基含己氧基偶氮苯基元新的一代碳硅烷光致变色液晶树状物G1及其偶氮基元化合物M3在各种溶液中的反顺光异构化反应速率常数、光回复异构化反应速率常数、热回复异构化反应速率常数、量子产率、活化能和异构转换率.G1和M3的光致变色速率常数为0.1s^-1,比对应的光致变色液晶聚硅氧烷的光响应速度快10⁷倍.     

非线性光学活性的侧链型聚丙二酸酯液晶的合成和性质

通过熔融缩聚法合成了含非线性光学活性硝基偶氮苯液晶基元的聚丙二酸酯侧链液晶聚合物 ,采用FTIR、NMR对其结构进行了表征 ,DSC确定其液晶转变温度 ,并用变温WAXD及偏光显微镜 (POM )研究其液晶性质 ,该聚合物为近晶型液晶聚合物 ,POM观察到典型焦锥织构 ,近晶相WAXD有对应层间距为2 74nm和 1 35nm的两个衍射峰 .聚合物旋涂膜经电晕极化 ,紫外光谱测试求得其取向序参数 =0 33 .     

零代光致变色液晶树状物的光响应行为研究

研究了含4个己氧基偶氮苯基元的零代(G0)光致变色液晶树状物在氯仿和四氢呋喃中的吸收光强、最大吸收波长、摩尔消光系数、量子产率、活化能、异构转换率、反-顺光异构化反应速率常数、热回复异构化反应速率常数、光回复异构化反应平衡常数及速率常数.G0的光致变色反应数率常数为10-1s^-1,而含偶氮基元液晶聚硅氧烷的光致变色反应数率常数为10^-8s^-1,前者比后者快107倍.     

不对称三环偶氮苯甲酸液晶的合成、光敏性及电化学性质

以4-烷基环己基甲酸(C1~C3)、4-烷基苯甲酸(C1~C5)和对羟基偶氮苯甲酸为主要原料,通过室温一步酯化反应,合成了2个系列8个不对称酯基偶氮苯甲酸类多官能团液晶化合物.目标产物的结构、液晶性及光敏性采用红外光谱(IR)、核磁共振谱(NMR)、质谱(MS)、元素分析、示差扫描量热分析(DSC)、热台偏光显微镜(HS-POM)和紫外-可见光谱(UV-Vis)等表征.利用循环伏安法(CV)测定了目标分子的前线轨道能级.测试结果表明,8个化合物均有液晶性,在甲醇溶液中显现出光敏性,在液晶态也观察到光顺反异构化.端烷基碳原子数对化合物紫外吸收峰Ⅱ(偶氮结构π-π*带)、HOMO能级、LUMO能级和能隙Eg存在奇偶效应影响.烷基为奇碳数化合物的Eg低于相邻烷基为偶碳数化合物.这与目标分子紫外光谱变化趋势相吻合,即Eg较小的化合物在紫外光谱中峰Ⅱ的吸收波长较长(能量较低),反之亦然.     

Synthesis and characterisation of photochromic dithienylcyclopentene liquid crystal with thermal irreversibility

A series of photochromic liquid crystal dithienylcyclopentene derivatives were synthesised from the initial material 2-chloro-5-methylthiophene. They were characterised by ¹H NMR, high resolution mass spectrometer, differential scanning calorimetry (DSC) and polarised optical microscopy (POM) with a hot stage. All of them exhibited excellent photochemically reversible isomerisation between the open-ring form and the closed-ring form in both organic solvents and LC media, resulting in the colour change between colourless and purple under different light irradiations. The typical textures from POM showed that their isomers both had nematic phase and smectic phase with different colours. These compounds with bent shape were more sensitive to light than those of diarylethenes reported.     

Preorganised effects of a tetramesogenic supermolecule on supramolecular assembly in the liquid crystalline phases

After preparing a homologous series of tetrameric mesogenic compounds in which two U-shaped molecules were connected via a rigid benzene derivative or a flexible alkyl chain, we investigated their phase transition behaviour using optical microscopy, differential scanning calorimetry and X-ray diffraction analysis. The compounds possessing an alkyl spacer as the central group exhibited nematic and smectic A phases just as the corresponding U-shaped molecule did. The compound possessing a 1,2-benzene unit as the connecting group showed nematic and smectic A phases, although the compound possessing a 1,3-benzene unit exhibited only an anticlinic smectic C phase. Structure–property relations of the liquid crystalline tetramers are interpreted in terms of preorganised effects of the four mesogenic units.     

Chiral and orientationally ordered fluid mesophases formed by oxadiazole bisaniline based achiral bent mesogens

Development of new liquid crystalline materials exhibiting interesting properties and phases continues to be an enabling enterprise in the forward march of their successful display and non-display applications. The design and synthesis of a homologous series of liquid crystalline bent-core compounds derived from the oxadiazole bisaniline moiety and the phase behavior of three members of the series that exhibit nematic, smectic C, and dark conglomerate phases is reported. The liquid crystalline phases exhibited by these mesogens are characterized using polarized optical microscopy, differential scanning calorimetry and x-ray scattering techniques. All three homologs prepared exhibit the nematic phase. Interestingly, the homolog with short hexyl terminal chains exhibits only the nematic phase that is stable over a very broad, nearly 100 K wide, temperature range. The compound with terminal octyl chains shows the chiral dark conglomerate phase below the nematic phase despite the bent molecules being achiral. The homolog with dodecyl alkyl chains is found to possess the smectic-C and two additional lamellar phases besides the nematic phase. These compounds enrich the library of achiral bent-core materials capable of exhibiting chiral and nematic phases.     

New mesogenic compounds possessing a biphenyl ester and ether moiety comprising 1,3-dimethylbarbituric acid: synthesis,characterisation and mesomorphic studies

New substituted derivatives of 5-vinyl-1,3-dimethylbarbituric acid were synthesised and evaluated for liquid crystal properties. Two sets of molecules were prepared. One end of all the molecules possesses the 1,3-dimethylbarbituric core. The first set comprises biphenyl ethers, 4a–n and the second set biphenyl esters, 5a–g. Liquid crystalline properties were investigated by POM and DSC techniques. All the compounds exhibited enantiotropic smectic A and nematic mesophases. The LC properties were found to depend on the spacer and terminal alkoxy- chain and alkoxy- ester moiety of the molecules. Smaller alkyl chain members showed a smectic phase, while higher alkyl chain members showed a nematic phase.     

含二苯并-18-冠-6酰胺型液晶冠醚钾配合物的合成和性质

合成了2个系列酰胺型液晶冠醚钾配合物，配合物的结构通过元素分析、IR、UV-Vis和AAS等方法表征。液晶行为通过DSC、POM、XRD等方法表征。实验结果表明，所有配合物均具有热致液晶性，且随分子末端烷氧基碳原子数增加，其熔点和清亮点呈规律性变化。与配体相比，配合物液晶态温度范围变宽。液晶相态类型发生改变，配体只有近晶相，而配合物既有近晶相，又有向列相。     

Competition between micro-segregation and anti-parallel alignment of an amphiphilic rod-like liquid crystal

Recently, we reported that a rod-like molecule, 4-[4-(7-hydroxyheptyloxy)phenyl]-1-(4-hexylphenyl)-2,3-difluorobenzene, exhibited a nematic phase with a layered structure and smectic C phases consisting of three states. We prepared a homologous series of the rod-like molecules in which a 2,3-difluoro-1,4-diphenylbenzene unit and a hydroxyl unit are connected via a flexible methylene spacer. We investigated their physical properties using polarised optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Although they showed nematic, smectic A and smectic C phases, the phase structures were found to depend on the flexible spacer length. Those compounds possessing a shorter spacer length than a heptyl unit exhibited bilayered smectic A and smectic C phases, whereas those possessing a longer spacer length than a heptyl unit showed conventional monolayered smectic A and smectic C phases. A nematic phase with a smectic-like layer ordering was observed for the compound possessing an octyl unit. The structure–property relations of the amphiphilic compounds are discussed.     

含偶氮基团的聚甲基丙烯酸酯型侧链液晶高分子的合成与表征

报道了一种新的含对甲氧基苯氨羰基偶氮苯基团的甲基丙烯酸酯单体及其自由基聚合产物的合成。利用元素分析,＾１Ｈ－ＮＭＲ、ＵＶ－Ｖｉｓ、ＧＰＣ、ＴＧ－ＤＴＡ、ＰＯＭ及Ｘ－射线衍射等手段对其结构与性能进行了表征。结果表明,偶氮单体不具有液晶性质,而聚合物则具有向列型液晶相存在,并且它在空气中具有很好的热稳定性。     

Liquid crystalline properties of 4‐hexyloxybenzylidene‐4′‐alkyloxyanilines

The liquid‐crystalline polymorphism of the homologous series of 4‐hexyloxybenzylidene‐4′‐alkyloxyanilines is investigated. Basing on the polarization microscopy (POM, TOA), the DSC calorimetry and miscibility studies the following mesophases were detected: nematic, smectic A, smectic C and smectic I. The phase diagrams of the compounds of these series with 4‐hexyloxybenylidene‐4′‐pentylaniline (as the standard of mesophases) show induction of the smectic F mesophases. Their dependence on the alkyl chain length and mole fraction is shown.     

含对硝基偶氮苯基团的侧链液晶高分子的合成及其光致变色性能研究

报道了新型的含对硝基偶氮苯基团的甲基丙烯酸酯单体与含介晶基团的甲基丙烯酸酯单体的合成及其自由基共聚合．利用１Ｈ ＮＭＲ、ＩＲ、ＵＶ Ｖｉｓ、ＧＰＣ、元素分析、ＤＴＡ及ＰＯＭ等手段对偶氮单体和聚合物进行了结构表征．证明两种单体的共聚合产物为无规共聚物，而且各聚合物在加热过程中均显示出明显的向列相液晶织构．研究了偶氮单体及其与介晶单体的共聚物的氯仿溶液和聚合物薄膜在紫外光诱导下的光异构化及热回复异构化行为．结果表明，它们在紫外光诱导下均能发生光致变色现象，而且介质对其光化学行为起决定作用．     

Synthesis and photoswitching properties of azobenzene liquid crystals with a pentafluorobenzene terminal

The fluorine-substituted benzoate ester rod-shaped liquid crystals containing an azobenzene side chain linked with terminal double bonds were synthesized and characterized.The mesophase and photoswitching properties were determined by polarizing optical microscopy(POM),differential scanning calorimetry(DSC) and UV-visible spectrometry.The rod-shaped compound 4a having an odd number of carbon atoms in the alkyl chains exhibits nematic phase and SmA type phase whereas compound 4b having an even number of carbon atoms showed only nematic phase.Both fluorinecontaining compounds 4c and 4d showed only SmA type phases.The photoswitching properties of these compounds showed a rate of trans to cis isomerization ranging 19-20 s,whereas reverse process took around 230 min in solution.These materials may be ideal in the field of optically rewritable applications where both on and off rates should be crucial.