Sawamura Masaya, Kawai Kenji, Matsuo Yutaka, Kanie Kiyoshi, Kato Takashi, Nakamura Eiichi
Department of Chemistry, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Nature. 2002 Oct 17;419(6908):702-5. doi: 10.1038/nature01110.
Polar liquid crystalline materials can be used in optical and electronic applications, and recent interest has turned to formation strategies that exploit the shape of polar molecules and their interactions to direct molecular alignment. For example, banana-shaped molecules align their molecular bent within smectic layers, whereas conical molecules should form polar columnar assemblies. However, the flatness of the conical molecules used until now and their ability to flip have limited the success of this approach to making polar liquid crystalline materials. Here we show that the attachment of five aromatic groups to one pentagon of a C(60) fullerene molecule yields deeply conical molecules that stack into polar columnar assemblies. The stacking is driven by attractive interactions between the spherical fullerene moiety and the hollow cone formed by the five aromatic side groups of a neighbouring molecule in the same column. This packing pattern is maintained when we extend the aromatic groups by attaching flexible aliphatic chains, which yields compounds with thermotropic and lyotropic liquid crystalline properties. In contrast, the previously reported fullerene-containing liquid crystals all exhibit thermotropic properties only, and none of them contains the fullerene moiety as a functional part of its mesogen units. Our design strategy should be applicable to other molecules and yield a range of new polar liquid crystalline materials.
极性液晶材料可用于光学和电子应用，近来人们的兴趣转向了利用极性分子的形状及其相互作用来指导分子排列的形成策略。例如，香蕉形分子在近晶层内使分子弯曲排列，而锥形分子应形成极性柱状聚集体。然而，迄今为止所使用的锥形分子的扁平度及其翻转能力限制了这种制备极性液晶材料方法的成功。在此我们表明，将五个芳基连接到C(60)富勒烯分子的一个五边形上可产生深度锥形分子，这些分子堆积成极性柱状聚集体。堆积是由球形富勒烯部分与同一列中相邻分子的五个芳基侧基形成的空心锥之间的吸引相互作用驱动的。当我们通过连接柔性脂肪链来延长芳基时，这种堆积模式得以保持，从而产生具有热致和溶致液晶性质的化合物。相比之下，先前报道的含富勒烯液晶都仅表现出热致性质，并且它们中没有一个将富勒烯部分作为其介晶单元的功能部分。我们的设计策略应适用于其他分子，并产生一系列新型极性液晶材料。
