Liquid crystalline bolaamphiphiles with semiperfluorinated lateral chains: competition between layerlike and honeycomb-like organization.
Liquid crystalline bolaamphiphiles with semiperfluorinated lateral chains: competition between layerlike and honeycomb-like organization.
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DOI：
10.1021/ja048224v
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发表时间：
2004-09
影响因子：
15
通讯作者：
Xiaohong Cheng;M. K. Das;U. Baumeister;S. Diele;C. Tschierske
中科院分区：
文献类型：
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作者：
Xiaohong Cheng;M. K. Das;U. Baumeister;S. Diele;C. Tschierske
通过钯催化的交叉偶联反应合成了一种新型的bola两亲性三嵌段分子，该分子由刚性联苯单元、极性的2，3-二羟基丙氧基和酚羟基组成，侧链为半全氟链。用偏光显微镜、DSC和X射线散射等方法研究了这些化合物的热致液晶行为，并研究了侧链长度对液晶性质的影响。具有最短链的化合物以及长链衍生物形成由bola两亲性部分的分离层和包含流体侧链的子层组成的层状中间相。短链化合物的层状相内的层采用位置相关性，导致2D晶格（Col（r）/p2 mm），而长链衍生物的层状相的层是不相关的（Lam）。具有中等链长的化合物组织成柱状相，其中非极性侧链分离成柱，其嵌入由bola两亲性单元组成的规则（Col（h））或拉伸（Col（r）/c2mm）六边形圆柱壳的网络中。总的来说，一个不寻常的相序列被发现，其中，相对于链长，柱状中间相之间发生层组织的两个中间相。
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.