铁电性液晶高分子的研究进展

铁电性液晶高分子的性能和合成方法，一直是国内外广泛关注与研究的热点。本文概述了铁电性液晶高分子的铁电性，光电效应，非线性光学性质，相转变及其合成的研究进展，并讨论了铁电性液晶高分子在显示和非线性光学领域中的应用前景。     

无机-有机杂化树枝状香蕉形液晶化合物的合成与表征

利用硅氢加成反应制备得到8个香蕉形液晶基元尾接于六面体倍半硅氧烷的8个顶点之上的杂化树枝状香蕉形液晶化合物.此化合物的化学结构通过核磁、红外、元素分析和GPC表征.一维和二维X-射线衍射研究表明,该化合物具有两个双层近晶C相;对样品施加三角波电压后显示该化合物具有反铁电性.     

手征性侧链液晶高分子取向结构的研究

用偏光显微镜,红外二色性和Ｘ 射线衍射研究了一种手征性侧链液晶高分子的相态织构和弛豫行为．偏光显微镜观察这种侧链液晶高分子冻结取向液晶态薄膜时,可观察到与剪切方向垂直的明暗相间的条带织构．红外二向色性的结果表明,取向态中侧链上的介晶基元倾向于与剪切方向垂直排列．取向和非取向膜的Ｘ射线衍射揭示了该侧链液晶高分子具有反铁电性液晶的两套反相螺旋结构．取向薄膜在液晶态的弛豫行为表明,取向作用能促进侧链高分子近晶相层状结构的生长,而且介晶基元的取向在弛豫过程中能保持下来．     

对-2,2,3,3,4,4,5,5-八氟戊氧基苯甲酸胆固醇酯的合成和液晶相变研究

液晶显示技术中主要应用的是向列相液晶,但是向列相液晶显示模式几乎已接近极限,从TN到STN直至TRF,对其应用没有新的理论模式.因而,人们将目光转移到了近晶相液晶上,目前各近晶相中的手性近晶C相,即铁电相引起人们广泛兴趣.铁电液晶具备向列相液晶所不具备的高速度(微秒级)和记忆性的优异特征,它们在最近几年得到大量研究.含氟链分子容易形成近晶A相和近晶C相,常作铁电液晶配方.这些铁电液晶(FLC)化合物包含一个或多个手性中心,而甾体可作为廉价的手性源,其衍生物有形成铁电相的可能.虽然理论已经预测到铁电现象在非手性液晶中也是可能的,但实际上长期以来铁电性只在手性分子的SmC*相中被发现.如Vill等[1]报道过包含一个长烷基链的甾类液晶,即对十六烷基苯甲酸胆甾醇酯和对十六环氧苯基碳酸盐,均显示了单变铁电性.Janulis等[2]已经列举(CH2)n作为氟化链和刚性核之间的空间间隔对获得介晶C相有利.我们在此报道对-2,2,3,3,4,4,5,5-八氟戊氧基苯甲酸胆固醇酯的合成及其液晶相变研究的结果.     

手性丙烯酸酯液晶原位光聚合反应

手性丙烯酸酯液晶原位光聚合反应何流，张树范，金顺子，漆宗能，王佛松（中国科学院化学研究所北京１０００８０）关键词手性丙烯酸酯，原位光聚合，双折射，近晶相手性侧链液晶高分子显示近晶Ｓ！相，具有铁电性，在光电功能材料和非线性光学材料方面有潜在的应用前景’...     

含L—氨基酸结构的手性液晶化合物的合成及其相变行为

合成了９种具Ｌ－氨基酸衍生物结构的介晶化合物、４种氨基酸衍生物和６种介晶化合物，新化合物的化学结构通过ＩＲ、＾１ＨＮＭＲ和元素分析证实，并用偏光显微观察和ＤＳＣ分析研究了其相变行为，结果表明有８种化合物呈现液晶相变。测定了它们的比旋光度，通过Ｘ射线射研究了化合物的近晶结构，证明其具铁电性。     

近期要目预告

荧光光谱在蛋白质分子构象研究中的应用(杨家祥　张元慧　陈真龙　刘清亮) 　　基质金属蛋白酶抑制剂设计的研究进展(成峰　柳红　罗小民　蒋华良　沈竞康　陈凯先) 　　渗透汽化分离芳烃/烷烃混合体系的研究进展(杨立明　徐利文　郭勇) 　　光敏异构化智能生物开关的研究(原义光　庄云龙) 　　液相组合化学研究进展(肖远胜　万伯顺　梁鑫淼) 　　可逆热色性化合物的研究进展(朱传方　徐汉红) 　　强化气流两相传质的研究进展(成弘　周明　余国琮) 　　超临界CO2流体萃取重金属的研究进展(文震　党志　余德顺) 　　噪声在非线性体系中的作用研究现状(张季谦　朱振明　辛厚文) 　　反铁电性液晶化合物研究现状(范星河　周其凤) 　　置换色谱及其在生物分子分离纯化中的研究进展(祁彦　黄骏雄)     

侧链含有蓝相液晶基元的聚硅氧烷液晶的合成及表征

采用蓝相小板块液晶单体反式-4-乙烯基-反式-4′-丙基双环己烷（3HHV）和反式-4-丙烯基-反式-4′-丙基双环己烷（4HHV）同时接枝到聚甲基含氢硅氧烷上,制备了聚硅氧烷侧链液晶聚合物。采用红外光谱和核磁共振氢谱对液晶单体及相应的聚合物进行结构表征,采用热台偏光显微镜,X-射线衍射和热分析对单体和聚合物的液晶行为及热性能进行研究。结果表明：液晶单体3HHV显示蓝相镶嵌织构,液晶单体4HHV显示胆甾相油纹状织构,它们的介晶区间温度分别为30.6°C和49.7°C,且均在低于室温就显示出液晶性。相应的液晶聚合物显示向列相纹影织构,介晶区间温度为192.6°C,在低于室温时也显示出液晶性,且热分解温度达到310°C以上,比其他环芳烃类介晶基元接枝聚硅氧烷主链的液晶聚合物具有更优越的热稳定性。     

多环单酯基芳香醛类液晶的合成与液晶相

以对羟基苯甲醛和一系列4-正丙基、4-正戊基取代的双环己基甲酸、联苯甲酸及环己基苯甲酸为主要原料,通过室温氯化、酯化等方法合成了4个C3和C5烷基取代的多环单酯基苯甲醛类液晶:4-(4-(反-4-丙基环己基)苯酰氧)苯甲醛、4-(反-4-(反-4-丙基环己基)环己酰氧)苯甲醛、4-(反-4-(反-4-正戊基环己基)环己酰氧)苯甲醛和4-(4-(4-正戊基苯)苯酰氧)苯甲醛。用元素分析1、H NMR、IR及MS测试技术表征了产物结构,通过DSC及POM(偏光显微镜)对其液晶相进行了研究。结果表明,在室温条件下的羧酸氯化可有效地抑制反式环己烷的构型转化;这类化合物具有热致液晶性,呈典型的向列相纹影及条纹织构,液晶相温度区间为107～156℃。     

端基含36个己氧基偶氮苯基元的二代碳硅烷光致变色液晶树状高分子的光化学研究

研究了含36个己氧基偶氮苯介晶基元的二代(G2)光致变色液晶树枝状高分子在氯仿和四氢呋喃溶液中的最大吸收波长,摩尔消光系数,反顺光异构化反应速率常数,光化学回复异构化正逆反应速率常数及其平衡常数,G2和G1的光致变色反应速率常数kp为10-1s-1,而含偶氮基元光致变色液晶聚硅氧烷的kp为10-8s-1,因此液晶树状高分子的光响应速率比后者快107倍.     

Impact of molecular structure of smectogenic chiral esters (3FmX1X2r) on vibrational dynamics as seen by IR and Raman spectroscopy

Smectogenic chiral esters with three-ring rigid core were examined by infrared and Raman spectroscopy. These compounds differ in the type of chiral centre, length of non-chiral chain and substitution of phenyl ring by fluorine atoms. The influence of molecular structure on the type of handedness of helical structure, as well as the shift and split of absorption bands on IR and Raman spectra were determined. The change of the length of non-chiral terminal chain has the most significant influence on the type of helical twist sense. All considered structural elements of tested compounds have the biggest influence on the value of wavelength of vibrational bands related to the carbonyl group located in the rigid core.     

Generation of frustrated liquid crystal phases by mixing an achiral nematic-smectic-C mesogen with an antiferroelectric chiral smectic liquid crystal

By mixing the achiral liquid crystal HOAB, exhibiting a nematic (N)-smectic-C (SmC) mesophase sequence, with the chiral antiferroelectric liquid crystal (AFLC) (S,S)-M7BBM7, forming the antiferroelectric SmC(a)(*) phase, at least seven different mesophases have been induced which neither component forms on its own: a twist-grain-boundary (TGB(*)) phase, two or three blue phases, the untilted SmA(*) phase, as well as all three chiral smectic-C-type "subphases," SmC(alpha)(*), SmC(beta)(*), and SmC(gamma)(*). The nature of the induced phases and the transitions between them were determined by means of optical and electro-optical investigations, dielectric spectroscopy, and differential scanning calorimetry. The induced phases can to a large extent be understood as a result of frustration, TGB(*) at the border between nematic and smectic, the subphases between syn and anticlinic tilted smectic organization. X ray scattering experiments reveal that the smectic layer spacing as well as the degree of smectic order is relatively constant in the whole mixture composition range in which AFLC behavior prevails, whereas both these parameters rapidly decrease as the amount of HOAB is increased to such an extent that no other smectic-C-type phase than SmC/SmC(*) exists. By tailoring the composition we are able to produce liquid crystal mixtures exhibiting unusual phase sequences, e.g., with a direct isotropic-SmC(a)(*) transition or a temperature range of the SmC(beta)(*) subphase of about 50 K.     

Structure and phase transition in self-assembled films of an anti-ferroelectric liquid crystal studied by two-dimensional correlation FTIR spectroscopy

The FTIR spectra were measured for a self-assembled film of the anti-ferroelectric liquid crystal (AFLC) molecules over a temperature range of 40-150 degrees C. The frequency and intensity variations of the infrared spectra were discussed in terms of changes in molecular orientation, conformation and intra- and/or inter-molecular interaction during phase transitions. The two-dimensional (2d) correlation analysis revealed that two hydrocarbon chains have different orientation behaviors, the shorter hydrocarbon chain is parallel to molecular long axis and the longer one is perpendicular to it. The splitting of the C=O stretching band indicated that the s-cis and the s-trans conformers of the ester group coexist in the self-assembly film. During the phase transitions, in mesogen part the C=O group adjacent to the chiral part is first response with temperature changing, following the C=O group between two phenyl rings, and eventually the phenyl rings; and the respondence with temperature of methyl is slower than that of methylene in alkyl chains.     

Optical switching and alignment of antiferroelectric liquid crystals containing an azo group

The optical properties of two kinds of photochromic antiferroelectric liquid crystal (AFLC) containing an azo group have been examined. Depending on the substituting group at the chiral centre, these AFLCs showed different photoinduced phase transitions by Ar⁺ laser light irradiation. This phase transition has led to a new form of optical switching controlled by a bias voltage. In addition, it was found that these AFLCs caused an azimuthal photoalignment effect regulated by linearly polarized Ar⁺ laser light irradiation. These phenomena were applied to image storage.     

Optical switching and alignment of antiferroelectric liquid crystals containing an azo group

The optical properties of two kinds of photochromic antiferroelectric liquid crystal (AFLC) containing an azo group have been examined. Depending on the substituting group at the chiral centre, these AFLCs showed different photoinduced phase transitions by Ar⁺ laser light irradiation. This phase transition has led to a new form of optical switching controlled by a bias voltage. In addition, it was found that these AFLCs caused an azimuthal photoalignment effect regulated by linearly polarized Ar⁺ laser light irradiation. These phenomena were applied to image storage.     

一种反铁电液晶薄膜相变过程的变温红外光谱研究

通过变温红外光谱对反铁电液晶MHOCPOOB薄膜相变过程中的分子构象、排布及相互作用的变化进行了研究.结果表明,室温时,薄膜中的分子烷基链同时含有zigzag和gauche两种构象.随着温度的升高,有序的zigzag构象转化为无序的gauche构象,链的扭曲程度增加.但S^*IA到S^*CA的转变并不引起烷基链构象和取向发生明显变化.刚性核中的羰基与相邻的苯环形成共轭体系,苯环之间相互倾斜排列,在相变过程中羰基与苯环的共平面作用逐渐被打破,且在相变点苯环间的二面角明显增大.     

Alignment and switching of AFLC materials using various boundary conditions

We have systematically studied the quality of bookshelf alignment and electro-optic characteristics of two antiferroelectric liquid crystal materials in cells with various boundary conditions. The electro-optic characteristics of the materials studied depend strongly on both the liquid crystal materials and the boundary conditions at the supporting substrates. We have compared a number of observations in these cells: the tendency to form AFLC domains in the virgin state and after switching; the surface electroclinic effect (SEC effect); the transmission-voltage characteristics (TV) when driven with triangular- and square-wave voltages at various frequencies; the threshold field and the conditions for relaxation to the AFLC state. The set of samples includes specially designed and manufactured test cells with different polyimides as alignment layers, treated with varying rubbing strengths. We discuss the significance of various factors and show the importance of simultaneously optimizing both materials and cell parameters for AFLC applications.     

Poly-γ-S-perillyl-l-glutamate and Poly-γ-S-perillyl-d-glutamate: Diastereomeric Alignment Media Used for the Investigation of the Alignment Process

Residual dipolar couplings (RDCs) offer additional information for structure elucidation by NMR spectroscopy. They are measured in anisotropic media, such as lyotropic liquid crystalline phases of polypeptides. Today, some suitable polypeptides are known. Nevertheless, structural influences of these polypeptides on the alignment properties are not really understood. Thus, which influence a chiral side chain has on enantiodiscrimination and whether we can improve the enantiodifferentiation significantly by adding an additional chiral center in the side chain are questions of interest. Therefore, new diastereomeric polypeptide-based alignment media with an additional chiral center in the side chain derived from perillyl alcohol were synthesized and their properties were investigated (secondary structure, liquid crystallinity, etc.). The enantiomers of isopinocampheol and β-pinene were used as model analytes for the study of enantiodiscrimination. Additionally, the usage of ¹H–¹H-RDCs to improve the alignment tensor quality is demonstrated.     

Preparation and evaluation of novel ferroelectric liquid crystalline cyclic siloxane tetramers

Two series of liquid crystalline cyclic siloxane tetramers, one containing the 2-methylbutyl chiral group and the other the 1-methylheptyl chiral group, were prepared to investigate, in a systematic manner, the role of molecular structure of (a) the spacer group, (b) the mesogenic side chain and (c) the chiral end group, on the liquid crystalline behaviour of these novel tetramers. The results from this systematic structure/property correlation study clearly showed the effect of the structure of both the chiral end group and the mesogenic side chain core on the thermal properties and temperature ranges of the SmC* phase (ferroelectric) exhibited by these novel materials. By the appropriate choice of spacer group, mesogenic side chain and chiral end group, a number of cyclic siloxane tetramers exhibiting wide SmC* ranges (ferroelectricity) around room temperature were synthesized.     

Preparation and evaluation of novel ferroelectric liquid crystalline cyclic siloxane tetramers

Two series of liquid crystalline cyclic siloxane tetramers, one containing the 2-methylbutyl chiral group and the other the 1-methylheptyl chiral group, were prepared to investigate, in a systematic manner, the role of molecular structure of (a) the spacer group, (b) the mesogenic side chain and (c) the chiral end group, on the liquid crystalline behaviour of these novel tetramers. The results from this systematic structure/property correlation study clearly showed the effect of the structure of both the chiral end group and the mesogenic side chain core on the thermal properties and temperature ranges of the SmC* phase (ferroelectric) exhibited by these novel materials. By the appropriate choice of spacer group, mesogenic side chain and chiral end group, a number of cyclic siloxane tetramers exhibiting wide SmC* ranges (ferroelectricity) around room temperature were synthesized.