侧基甲壳效应和甲壳型液晶高分子

侧链液晶高分子体系里,液晶基元可以通过尾接或腰接的方式与主链相连.一般认为,在液晶基元与主链间插入一段长度合适的＂柔性间隔基＂可有效实现主、侧链间的动力学去偶合,从而有利于侧基液晶基元之间的有序排列.作为一类特殊的腰接型侧链液晶高分子,甲壳型液晶高分子中体积较大的侧基（如棒状液晶基元）通过非常短的间隔基或仅通过一个碳-碳键直接横挂至主链上,这导致了强烈的甲壳效应,使得主链被迫伸展.因此,可从与＂柔性间隔基＂完全不同的角度出发,充分利用主链和侧基间的偶合作用,设计甲壳型液晶高分子.本文综述了腰接型侧链液晶高分子中的侧基甲壳效应、甲壳型液晶高分子中由主链与侧基相互作用所导致的特殊构象以及液晶相结构.研究表明,侧基甲壳效应在调控甲壳型液晶高分子的形状、尺寸以及螺旋结构等方面有重要作用.甲壳型液晶高分子可作为刚-柔嵌段共聚物的刚性链段,也可作为主/侧链结合型液晶高分子的主链部分参与到多层次分级超分子有序结构的构筑之中.     

含柔性间隔链段的芳香共聚酯热致性液晶高分子的结构研究

本文用富里叶红外光谱方法研究了一系列柔性间隔链段长度不等的芳香共聚酯热致性液晶高分子。测定了它们的变温光谱和偏振性质。并将谱带的变温行为与液晶转变相关联。结果表明,芳香共聚酯热致性液晶中液晶基元之间的相互作用很强而柔性间隔链之间的相互作用很弱。柔性间隔链段主要是伸直的反式构象。从一些谱带的二向色性估算了体系的有序度参数以及取向角。分子链的取向程度随柔性间隔链段长度的增加而减小。     

刚柔相嵌液晶高分子的赝二级相变温度

讨论了刚柔相嵌液晶高分子的向列相一各向同性相转变与其分子结构的关系．给出了该一级相变的赝二级相变温度Ｔ＊与这类液晶高分子的液晶基元和间隔基的长度、柔顺性（相关长度）以及它们之间的相互作用的关系的解析表示式．分析了液晶基元与间隔基连接处的表观弯曲（接口效应）对Ｔ＊的影响．文中的结论与实验相符．     

刚柔相嵌液晶高分子的赝二级相变温度

讨论了刚柔相嵌液晶高分子的向列相－各向同性相转变与其分子结构的关系，给出了该一级相变的赝二级相变温度Ｔ与这类液晶高分子的液晶基元和间隔基的长度，柔顺性（相关长度）以及它们之间的相互作用的关系的解析表示式，分析了液晶基元与间隔基连接处的表观弯曲（接口效应）对Ｔ的影响，文中的结论与实验相符。     

一类新的刚性链侧链型液晶高分子的合成

以自由基聚合方法，合成了一系列含有三个苯环通过酯键相联的液晶性单体及其聚合物．在这类新的液晶高分子中，刚性液晶基元不通过柔性间隔基而直接竖挂在聚甲基丙烯酸酯大分子主链上．这些高分子有很高的玻璃化转变温度，表明其分子链刚性较大，因而代表了一类新的刚性链侧链型液晶高分子．它们的液晶行为用ＤＳＣ、偏光显微镜和Ｘ－光衍射进行了表征．发现所有单体和聚合物均为向列型热致性液晶．     

侧链聚硅氧烷液晶高分子的合成与表征及应用研究

液晶高分子既具有独特的液晶性 ,又具有高分子的良好材料性能 ,引起了人们的广泛注意[1～ 9] .侧链液晶高分子大多可以作为功能材料 ,对它们的研究有很大的理论与现实意义 .以往报道的此类化合物的介晶基元大多是通过烷氧基与间隔基相连[10 ] .我们以催化活性很高的铂络和物为催化剂 ,通过硅氢加成反应制备了间隔基与介晶基元通过酰氧基相连的两种侧链聚硅氧烷液晶高分子 ,并对它们的性质进行了初步表征 .发现它们具有很好的液晶性 .已有研究表明侧链聚硅氧烷液晶在气相色谱分离结构近似的物质方面 ,具有易涂渍、选择性及热稳定性优于低分子…     

含X-型和棒型两种液晶基元的主链型系列芳族共聚酯的研究

采用含X-型和棒型液晶基元的两种不同单体,通过改变X-型液晶基元单体的结构和柔性链段长度,经高温溶液缩聚,合成了一系列主链型共聚液晶高分子.研究发现,所有样品都具有很好的热致液晶性及宽广的液晶态温度范围.随单体结构改变,共聚物的相转变温度大致呈规律性变化.     

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．     

含X-型和棒型两种液晶基元的主链型系列芳族共聚酯的研究

 采用含X-型和棒型液晶基元的两种不同单体,通过改变X-型液晶基元单体的结构和柔性链段长度,经高温溶液缩聚,合成了一系列主链型共聚液晶高分子.研究发现,所有样品都具有很好的热致液晶性及宽广的液晶态温度范围.随单体结构改变,共聚物的相转变温度大致呈规律性变化.     

主链具有X-型液晶基元的液晶高分子系列的合成与研究

以低温溶液缩聚方法,合成了一系列主链上具有X-型液晶基元的液晶高分子。所有聚合物样品均具有明显的热致液晶性。不同柔性链段长度和取代基对聚合物的液晶性呈规律性的影响。并用IR、H-NMR、WAXD和热台偏光显微镜等方法对聚合物进行了表征。     

SYNTHESES AND CHARACTERIZATION OF A NEW TYPE OF LIQUID CRYSTALLINE POLYESTERS

A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of the mesogenic unit were synthesized by interfacialpolymerization of diacyl chlorides in 1, 2-dichloroethane and 2, 4-dihydroxy-4'-nitroazobenzen inaqueous alkaline solution. The polyester structures were confirmed by proton NMR and IRspectra. Their phase transition behavior and texture were studied by polarizing microscopy andDSC.     

THE EFFECT OF SUBSTITUENT ON THE THERMAL PROPERTIES OF POLYESTERS CONSISTING OF AROMATIC TYPE SCHIFF BASE MESOGENIC UNITS AND POLYMETHYLENE SPACERS

Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2" positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.     

SYNTHESIS AND PROPERTIES OF NEW MESOGEN-JACKETED LIQUID CRYSTALLINE POLYMERS*

Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, andmesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of thesepolymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Theirliquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. Theresults show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2)a flexible spacer will decrease the "Jacket Effect" and the liquid crystallinity and 3) a subtle modification of the terminalgroups on the mesogenic unit may also have a significant influence on properties of the polymers.     

SYNTHESIS OF NOVEL LIQUID CRYSTALLINE POLY(METH)ACRYLATES CONTAINING SILOXANE SPACER AND TERPHENYLENE MESOGENIC UNIT*

Novel side-chain liquid-crystalline poly(meth)acrylates were synthesized using 1-(3-hydroxyl-propyl)-3-[(4"-cyano-p-terphenyloxycarbonyl)alkyl]-1,1,3,3-tetramethyldisiloxane as the key intermediate. The polymers used a disiloxanemoiety as decoupling spacer with cyano-p-terphenyl as mesogenic unit. The products were characterized by NMR, GPC,DSC and polarizing optical microscopy. All the polymers with cyano-p-terphenyl mesogens formed a stable mesophase.However, if the mesogenic unit is replaced by cyano-p-biphenyl, the liquid crystalline character will be lost. The results alsoshowed that the decoupling is incomplete even if a complex and very flexible decoupling spacer is deliberately incorporatedto obtain the highest possible decoupling effect.     

Influence of the mesophase structure on the β-relaxation in liquid crystalline poly(meth)acrylates

The dependence of the rotation of the mesogenic unit around its long axis (β-relaxation) on the actual mesophase in liqid crystalline polymethacrylates and polyacrylates was studied by dielectric spectroscopy in the frequency range from 10⁻² Hz to 10⁶ Hz and in a temperature range from 170 K to 430 K. As mesogenic units derivatives of (p-alkoxy-phenyl)-benzoate were used where different mesophases were achieved by small variation of the mesogenic structure, the spacer length and the tail group of the mesogenic unit. For all samples the temperature dependence of the relaxation rate of the β-relaxation can be described by an Arrhenius equation where both the pre-exponential factor and the activation energy increase significantly with the order of the mesophase. To characterize the structure X-ray measurements were also carried out. The mean lateral mesogenic distance was correlated directly with relaxational quantities.     

Synthesis and properties of two new series of isomeric liquid crystalline polyesters with conjugated double bonds

Two homologous series of flexible main chain liquid crystalline polyesters with isomeric mesogenic groups containing conjugated double bonds, were synthesized and studied by differential scanning calorimetry and optical microscopy. One series (S1) has the p-phenylene-diacryloyloxydibenzoyl moiety as a mesogenic unit. The other (S2) has the terephtaloyl dioxydicinnamoyl moiety as a mesogenic unit. The reactivity of the conjugated double bonds of the p-phenylenediacryloxy unit, at the temperature of mesophase formation, impedes the stability of liquid crystalline mesophases of polymers of series (S1). Two low molecular weight analogues of polymers were also prepared and their properties compared with those of polymers of similar structure. The two model compounds form stable smectic mesophases over a wide range of temperatures, which shows the high mesomorphogenic ability of both mesogenic units.     

聚对偶氮氧苯酚酯系列热致性液晶高分子的相转变

合成含有不同亚甲基数（ｎ＝４—１２，１４）的主链型热致性液晶高分子──聚对偶氮氧苯酚二元羧酸酯．用ＤＳＣ和ＦＴＩＲ观测了相转变的奇偶效应，揭示了液晶相转变过程中分子间相互作用力性质的变化．并与聚２，２＇－二甲基对偶氮氧苯酚二元羧酸酯系列进行了比较，讨论了中介单元的对称性对液晶高聚物相转变和对液晶相稳定性的影响．     

Thermotropic polyesters with main chain isomeric naphthylene,trans-1,4-cyclohexylene,and 2,5-pyridinediyl units: The importance of the order of ester linkages in the mesogenic units

Two new series of thermotropic polyesters were prepared and their mesomorphic properties were investigated. The polymers consist of triad aromatic ester-type mesogenic units with decamethylene spacers. The mesogenic units of the first series are composed of isomeric dihydroxynaphthalene moieties as the central structure flanked by two p-oxybenzoyl groups. In the second series the mesogenic units were of reversed ester linkages: the central moieties, derived from 1,4-naphthalene dicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, or 2,5-pyridinedicarboxylic acid, are connected on both sides to p-phenylene structures. Two low molecular weight model compounds with 1,4-naphthylene unit at the center of the mesogenic unit were synthesized and their mesomorphic properties were compared with those of corresponding polymers. It was observed both for the model compounds and the polymers containing 1,4-naphthylene units that the linking order of the ester group in the mesogenic unit exerted a decisive influence on the capability for the formation of a mesophase. Thermal and mesomorphic properties were investigated by DSC, on a polarizing microscope equipped with a hot-stage, and by visual observation of stir-opalescence of the melts.     

Main chain thermotropic polyesters having flexible spacers—influence of ester group linking order between mesogenic unit and flexible spacer

Two series of main chain thermotropic polyesters having a decamethylene spacer were prepared and their thermal transitions and liquid crystalline properties were studied. The linking sequence of the ester bond between the mesogenic unit and spacer, i.e., versus with M and S being mesogenic unit and spacer, respectively, was found to influence profoundly the nature of the mesophase formed by the polymers. The former favors the formation of a smectic phase, while the latter favors the formation of a nematic phase. The structure of the central dicarboxylic acid moiety of the triester mesogenic units also was found to influence greatly the polymer's ability to form mesophases.     

手性聚甲基丙烯酸酯液晶聚合物的合成及相行为的研究

手性聚甲基丙烯酸酯液晶聚合物的合成及相行为的研究向前，张纪宇，张树范（中国科学院化学研究所北京１０００８０）关键词手性液晶聚合物，相行为手性侧链液晶聚合物在侧链中含有不对称碳原子的末端基，使聚合物显示Ｓｔ相．Ｓ？相层中的分子呈倾斜排列而产生自发极化．...