Kolbel M, Beyersdorff T, Tschierske C, Diele S, Kain J
Institut fur Organische Chemie, Martin-Luther-Universitat Halle-Wittenberg, Germany.
Chemistry. 2000 Oct 16;6(20):3821-37. doi: 10.1002/1521-3765(20001016)6:20<3821::aid-chem3821>3.0.co;2-8.
Rodlike amphiphilic molecules that contain exclusively aromatic building-blocks and no flexible alkyl chains have been synthesized and their mesomorphic properties investigated. These novel compounds bear diol head groups of different size (2,3-dihydroxypropyloxy or 5,6-dihydroxy-3-oxahexyloxy groups) at one end of a biphenyl unit, various aromatic segments (benzyloxy, 4-, 3-, or 2-methylbenzyloxy, phenoxy groups) at the other, and additional methyl substituents in different positions. They were synthesized by using Suzuki cross-coupling reactions as the key steps. Their thermotropic mesomorphism was investigated by means of polarized light optical microscopy, differential scanning calorimetry, and, for enantiotropic phases, by X-ray scattering. The liquid crystallinity of this class of compounds is influenced by protic solvents, such as water and glycerol. Dependent on the temperature and the solvent content, different SA phases were found. Several mesophases resulting from the frustration of these layer structures (e.g., different columnar phases, optical isotropic mesophases, and nematic phases) were also present. The smectic phases have different degrees of intercalation (SAd, SA2). The columnar phases are supposed to be ribbon structures that result from the collapse of the smectic layers. They occur in some pure compounds or they are induced upon the addition of protic solvents. The particular phase sequences of the different compounds depend mainly on the position of the methyl substituents at the biphenyl cores and are largely determined by the degree of intercalation of the aromatic cores.
已合成了仅含有芳香结构单元且无柔性烷基链的棒状两亲分子，并对其介晶性质进行了研究。这些新型化合物在联苯单元的一端带有不同大小的二醇头基（2,3 - 二羟基丙氧基或5,6 - 二羟基 - 3 - 氧杂己氧基），另一端带有各种芳香片段（苄氧基、4 - 、3 - 或2 - 甲基苄氧基、苯氧基），以及在不同位置的额外甲基取代基。它们是通过铃木交叉偶联反应作为关键步骤合成的。通过偏光光学显微镜、差示扫描量热法以及对于互变液晶相通过X射线散射研究了它们的热致介晶现象。这类化合物的液晶性受质子性溶剂（如水和甘油）的影响。根据温度和溶剂含量，发现了不同的SA相。还存在由这些层状结构的受挫产生的几种中间相（例如不同的柱状相、光学各向同性中间相和向列相）。近晶相具有不同程度的插层（SAd、SA2）。柱状相被认为是由近晶层的塌陷产生的带状结构。它们出现在一些纯化合物中，或者在加入质子性溶剂时被诱导产生。不同化合物的特定相序列主要取决于联苯核上甲基取代基的位置，并且在很大程度上由芳香核的插层程度决定。
