Cheng Xiaohong, Das Malay Kumar, Baumeister Ute, Diele Siegmar, Tschierske Carsten
Contribution from the Institute of Organic Chemistry, University Halle, Kurt-Mothes-Strasse 2, D-06120 Halle, Germany.
J Am Chem Soc. 2004 Oct 13;126(40):12930-40. doi: 10.1021/ja048224v.
Novel bolaamphiphilic triblockmolecules consisting of a rigid biphenyl unit, with a polar 2,3-dihydroxypropyloxy group and a phenolic OH group at opposite ends, as well as a semiperfluorinated chain in a lateral position have been synthesized via palladium catalyzed cross coupling reactions as the key steps. The thermotropic liquid crystalline behavior of these compounds was investigated by polarized light microscopy, DSC and X-ray scattering, and the influence of the length of the lateral chain on the mesomorphic properties was studied. The compound with the shortest chain as well as the long chain derivatives form lamellar mesophases composed of segregated layers of the bolaamphiphilic moieties and sublayers comprising the fluid lateral chains. The layers within the lamellar phases of the short chain compound adopt a positional correlation, leading to a 2D lattice (Col(r)/p2mm), whereas the layers of the lamellar phases of the long chain derivatives are noncorrelated (Lam). Compounds with a medium chain length organize into columnar phases, where the nonpolar lateral chains segregate into columns, which are embedded in networks of regular (Col(h)) or stretched (Col(r)/c2mm) hexagonal cylinder shells consisting of the bolaamphiphilic units. In total, an unusual phase sequence was found, where, with respect to the chain length, columnar mesophases occur between two mesophases with layer organization.
通过钯催化交叉偶联反应作为关键步骤，合成了新型两亲性三嵌段分子，该分子由一个刚性联苯单元组成，在相对两端分别带有一个极性2,3 - 二羟基丙氧基和一个酚羟基，并且在侧位带有一个半全氟链。通过偏光显微镜、差示扫描量热法和X射线散射研究了这些化合物的热致液晶行为，并研究了侧链长度对介晶性质的影响。最短链的化合物以及长链衍生物形成层状中间相，该中间相由两亲性部分的隔离层和包含流体侧链的子层组成。短链化合物层状相内的层具有位置相关性，形成二维晶格（Col(r)/p2mm），而长链衍生物层状相的层是不相关的（Lam）。中等链长的化合物组织成柱状相，其中非极性侧链聚集成柱，这些柱嵌入由两亲性单元组成的规则（Col(h)）或拉伸（Col(r)/c2mm）六方圆柱壳网络中。总体而言，发现了一种不寻常的相序列，就链长度而言，柱状中间相出现在两个具有层状结构的中间相之间。
