氰乙基羟丙基壳聚糖的溶致和热致液晶性研究

从壳聚糖出发先羟丙基化再氰乙基化,合成了氰乙基羟丙基壳聚糖(羟丙基的摩尔取代度为3.2,氰乙基的取代度为1.0).氰乙基羟丙基壳聚糖(CNHPCS)和羟丙基壳聚糖(HPCS)两者都有胆甾型溶致液晶性,浓溶液呈现指纹状织构.在二氯乙酸中,前者的临界浓度(29%,质量分数,下同)高于后者(17%).这一结果可以用引入氰乙基增加了分子间作用力从而使得链刚性增加来解释.CNHPCS在熔点193℃和分解温度220℃之间很窄的温区内观察到有热致液晶胆甾相.CNHPCS固体膜的胆甾相螺距采用激光小角光散射法测定,结果与偏光显微镜测得的数值一致.     

甲壳素类液晶高分子的研究Ⅱ-侧基长度和取代度对羧酰化壳聚糖的液晶性的影响

五种羧酰化壳聚糖即乙酰化、丙酰化、丁酰化、己酰化和庚酰化壳聚糖在二氯乙酸溶液中均呈现胆甾型溶致液晶相．临界浓度随侧基长度的增加而增加,但取代度（ 从０－２１ 变化到０－９４） 对临界浓度没有影响．在两相共存浓度区内,均呈现典型的滴状织构．从两相共存到完全液晶相的转变浓度也随侧基长度的增加而增加．     

N-烷基壳聚糖的合成及其溶致液晶行为

合成了一系列具有不同取代基(甲基、乙基、丙基、丁基)的壳聚糖衍生物——N 烷基壳聚糖,通过控制反应物摩尔比获得了一系列不同取代度的产物.不同取代基及不同取代度的衍生物均具有溶致液晶性,考察了同一碳链不同取代度和相近取代度不同碳链长度的衍生物对其液晶临界行为的影响.结果表明：同一碳链长度时,取代度对临界浓度的影响不大;而当取代度相近时,随着碳链长度增加,临界浓度也随之增大.此结果与Onsager和Flory的刚性棒理论相符.粉末X射线衍射实验进一步证实了这一结果.     

甲壳素类液晶高分子的研究：Ⅱ.侧基长度和取代度对羧酰化壳聚糖的？…

五种羧酰化壳聚糖即乙酰化、丙酰化、丁酰化、己酰化和庚酰化壳聚糖在二氯乙酸溶液中均呈现胆甾型致液晶相。临界浓度随侧基长度的增加而增加，但取代度（从０．２１变化到０．９４）对临界浓度没有影响。在两相共存浓度区内，均呈现典型的滴状织构。从两相共存到完全液晶相的转变浓度也随侧基长度的增加而增加。     

氰忆内基壳聚糖的溶致和热致液晶性研究

从壳聚糖出发先羟丙基化再氰乙基化,合成了氰乙基羟丙基壳聚糖,氰乙基羟丙基壳聚糖（ＣＨＮＨＰＣＳ）和羟丙基壳聚糖（ＨＰＣＳ）两者都有胆甾型溶致液晶性,浓溶液 纹太织构,在二氯乙酸中,前者的临界浓度２９％,质量分数,下同）高于后者（１７％）,这一结果可以用引入氰乙基增加了分子间作用力从而使得链刚性增加来解释,ＣＮＨＰＣＳ在熔点１９３℃和分解温度２２０℃之间很窄的温区内观察到有热致溶液晶胆寻相,ＣＮＨＰ     

壳聚糖液晶溶液的性能

制备了聚糖液晶溶液,并采用偏光显微镜(POM)、流变仪、差示扫描量热仪(DSC)等分别对液晶织构、黏度、相转变性能进行了研究.结果表明:壳聚糖呈现典型的胆甾相液晶织构;其溶液黏度随浓度及剪切力的变化规律符合高分子液晶溶液的变化规律;在DSC升、降温曲线上分别存在吸热峰和放热峰.     

丁酸壳聚糖液晶的织构研究

用偏光显微镜研究了一种新的液晶高分子－丁酸壳聚糖液晶的织构。丁酸壳聚糖能溶于十多种溶剂中形成胆甾型液晶相。指纹状织构是主要织构，此外还观察到鲜偏振场织构、滴状织构、平面织构和条带织构等，与纤维素衍生物的液晶态结构很相似。     

乙基氰乙基纤维素／聚丙烯酸复合物及大分子胆甾型液晶相的形态结构特征

对乙基氰乙基纤维素／丙烯酸胆甾型液晶溶液的液晶性，液晶态的织构特征，丙烯酸在液晶溶液中的聚合反应及在反应过程中胆甾型液晶相结构和性能的变化等方面进行了研究，     

纤维素共混型液晶的光学性能与结构

利用紫外-可见分光光度计, X射线衍射仪与偏光显微镜研究了乙基纤维素(EC)与羟丙基纤维素(HPC)共混型胆甾液晶. 研究发现: 质量百分浓度相同时, 共混纤维素胆甾型液晶的最大反射波长与螺距随着共混物中HPC含量的增加而增大. XRD实验结果表明共混型纤维素液晶螺距增大与液晶体系中分子层间的距离增大相关. 可以利用该现象来调控纤维素胆甾型液晶的光学性能与螺距.     

基于胆甾相液晶的可调制光子晶体

将胆甾相液晶填充进胶体晶体内部空隙, 通过胆甾相液晶与胶体晶体的耦合, 构建了一种新型可调制液晶光子晶体. 填充于胶体晶体内部的胆甾相液晶织构呈现典型的手性近晶相(S)特征. 由于胆甾相液晶具有特定的选择性反射, 当胶体晶体的带隙处于胆甾相液晶的反射波长范围之内, 则随着温度的改变, 胶体晶体的带隙与胆甾相液晶的带隙同时发生蓝移. 在一定温度条件下, 胆甾相液晶的带隙将与胶体晶体的带隙发生耦合, 实现了光子晶体带隙在单峰与双峰之间的可逆切换.     

Textures and defects in lyotropic liquid crystals of ethyl-cyanoethyl cellulose

Textures and defects in ethyl-cyanoethyl cellulose [(E-CE)C]/dichloroacetic acid (DCA) cholesteric liquid crystalline solutions and in (E-CE)C/polyacrylic acid (PAA) composites were observed and studied by polarizing microscopy and electron microscopy. The existence of χ, λ and τ disclinations were observed in the mesophase with disk-like and band-like textures. Pairs of disclinations with different signs were also found in the mesophase with the band-like texture. Domain walls were observed in (E-CE)C/PAA composite films with cholesteric order by TEM. The orientation of polymer chains in the vicinity of the core of the disclinations is discussed.     

TEXTURES OF ETHYL-ACETYL CELLULOSE MESOPHASE

There was phase separation between the anisotropic and isotropic phases in the ethyl-acetyl cellulose/dichloroacetic acid cholesteric liquid crystalline solutions .The textures of mesophase varied with the concentration. The mesophases could form the disc-like texture, oily streaks texture and texture of domains gathered randomly. In the first two textures the layers of the ordered molecular chain were perpendicular to the slide surface and the axes of the helical structure were parallel to the slide surface.     

丁酸壳聚糖液晶的临界行为研究

用偏光显微镜法测定了丁酸壳聚糖在四种酸性溶剂中的临界浓度值．发现临界浓度值（ｖ／ｖ％）与溶剂的酸性无关，都是１６％～１７％．在以二氯乙酸为溶剂时，不同丁酰化程度的丁酸壳聚糖有相同的临界浓度．用ＤＳＣ法测定了丁酸壳聚糖／二氯乙酸体系的临界温度，并绘制了相图．结果表明，浓度达６０％（ｗ／ｗ％）后，临界温度基本不再变化，稳定在３９℃左右．     

乙基醋酸纤维素液晶态条带织构的形成机理

本文应用平行板移动式和转动式二种剪切装置研究了乙基醋酸纤维素的二氯乙酸体系液晶态受剪过程形成条带织构的临界剪切速率,条带织构的形成机理以及所形成的条带织构在升降温过程中的变化。结果表明,高分子液晶态受剪过程条带织构不是在受剪时产生,而是在受剪停止后的弛豫过程中形成的。可以观察到条带织构出现的诱导时间(t_b),其值的大小与溶液的浓度、剪切速率等因素有关。最后提出一模型来解释高分子液晶态受剪切过程条带织构的形成机理。     

Effect of core group substituents on the monomer mesophase,photocuring, and film viscoelastic properties of mesogenic diacrylates

In this paper, the influence of molecular structure variations on the mesophase behavior, photocurability, and film properties of polymerizable mesogenic diacrylates is reported. The effect of methoxy or chloro substituent on the mesophase behavior of the monomers, present at the 2‐position of the phenylene core, in comparison to the unsubstituted core, has been studied using thermal and photo‐DSC techniques. These monomers were used in combination with a chiral dopant to form cholesteric mesophases, which was subsequently crosslinked through photopolymerization. Optical microscopy and polarized optical microscopy (POM) were used to study the morphology of monomers as well as the photopolymerized films. Optical images show the influence of chiral dopant on the texture present in the films, both before and after the crosslinking. POM images show the mesophase present in the monomers and the free films. Evaluation of viscoelastic properties of the photocured films demonstrates the influence of mesogenic core substituents on the network transition temperature, modulus, and damping characteristics. Copyright © 2008 John Wiley & Sons, Ltd.     

THE STRUCTURE AND OPTICAL PROPERTIES OF COPOLYMER OF CHOLESTERIC ESTER

The structure and switching properties of liquid crystalline side chain copolymers of cholesteric ester of 1,2-hydroxypropyl 2,4-di-isocyanatoluene methylmethacrylate (PHCPM) have been studied in detail. The cholesteric mesophase of PHCPM is shown by polarizing microscopy, X-ray diffraction and selective light reflection. Solution of PHCPM in CHCl_3 is optically anisotropic; its optical properties were determined by specific rotation [α], circular dichroism (CD) and wide-angle hght scattering (WALS) methods.     

含薄荷基的手性液晶单体的合成、结构与性能研究

合成了五种新型含薄荷基的手性单体(M1～M5), 它们的结构、纯度及旋光性质通过了1H NMR, FT-IR、元素分析仪及旋光仪等手段的表征, 采用DSC, POM, UV/Vis/NIR等研究了单体的介晶性能、相行为及选择反射性能. 结果表明: 单体的比旋光度值随苯环数目的增加而降低, 通过在薄荷基与液晶核之间引入柔性间隔基元, 实现了含薄荷基单体具有液晶性能的目的. 除M1外, 其余四种单体均呈现手性近晶C (SC*)相和胆甾(Ch)相, 此外M5还出现了蓝相织构. M2～M4只在SC*相区能观察到选择反射现象, 而M5在SC*相区和Ch相区均出现明显的选择反射现象, 且随温度的升高, SC*相区的反射波长发生“红移”, 而Ch相区的反射波长则发生“蓝移”. 随着液晶核刚性的增加, 对应单体的熔点和清亮点增大, 液晶相范围变宽. 液晶核中的酯基桥键与组合方式也对单体的熔点和清亮点具有一定的影响.     

侧链胆甾液晶聚合物及弹性体的液晶性能研究

把胆甾液晶单体 4 烯丙氧基苯甲酸胆甾醇酯 (Mch)分别和向列液晶单体 4 烯丙氧基苯甲酰氧基 4′ 甲氧基苯 (Mn) ,向列液晶交联剂 2 叔丁基对苯二酚双 [4 (6 丙烯酰氧基己氧基 )苯甲酸酯 ](Mnc)接枝到聚硅氧烷链上 ,得到系列侧链液晶聚合物Pn 系列和液晶弹性体Pe 系列 .通过热分析、偏光显微分析和X 射线分析等手段分别研究了向列液晶单体和向列液晶交联剂对含同一胆甾液晶基元聚合物的影响 .结果表明 ,向列液晶单体的摩尔百分比在 80 %以下 ,液晶聚合物Pn 系列为胆甾型液晶 ,在研究的范围内 ,液晶弹性体Pe 系列也为胆甾型液晶 ,Pn 系列和Pe 系列都具有较宽的液晶相范围 ,热分解温度均在 2 80℃以上 .     

磁场对乙基纤维素胆甾型液晶相的影响

高分子胆甾型液晶相是一个在高分子和液晶领域都引起广泛兴趣的课题,不仅因为自然界中的多种生物大分子,如纤维素,多肽,DNA等可以形成胆甾型液晶相;而且由于胆甾相具有特殊的螺旋结构(如图1所示),能产生一些特殊的光学性能,如强烈的旋光性,圆二色性和选择性反射光性能等;并带来相应的应用,正是由于高分子胆甾相材料的性能和应用,使得高分子胆甾相液晶的相态转变和结构变化也一直倍受关注。     

Synthesis and characterization of a trefoil-shaped liquid crystal based on 1,3,5-triazine with carbazole groups

A trefoil-shaped liquid crystal containing an aromatic hetero-nucleus has been synthesized by the reaction of cyanuric chloride with 3,6-didecanoyl carbazole (DDC). The molecular structure was characterized by ¹H NMR and ¹³C NMR spectroscopy, mass spectroscopy and elemental analysis. The core consists of 1,3,5-triazine directly linked to three carbazole groups. The trefoil-shaped conformation is suggested by molecular modelling. The mesophase was investigated using DSC, X-ray diffraction and polarizing optical microscopy. The X-ray diffraction pattern of a sample cooled slowly from the isotropic state showed sharp peaks in the small angle and wide angle regions implying the existence of a columnar phase with interand intra-columnar ordering. An unusual reticular texture similar to a cholesteric texture was observed.