不同拓扑构型嵌段液晶分子的合成与相变行为

本文对近来报道的三类嵌段液晶分子：多羟基1－苯甲酰胺－2，3－丙二醇两亲性分子I,星状季戊四醇苯甲酸酯II及带侧链的波拉化合物III的合成及自组装行为作了综述。这些分子由各向异性嵌段、两亲性嵌段和烷基链（或全氟链）以不同的拓扑形式组合而成，其合成的关键步骤是Pd(0)催化下碘代全氟烷烃对双键的自由基加成反应以及Pd(0)催化的偶合反应。通过调节亲水部分和亲脂部分的比例, 在I和II-F中观察到了从近晶层相（Sm）到柱相（Col）再到三维立方相（Cub）的液晶相序列；在波拉分子III-F中通过改变侧链的长度, 获得了一系列柱相及新型层相。这些研究表明, 利用多元化竞争组合理念，将分子中不相容的部分以不同的拓扑形式结合在一起，通过它们的微观相分离, 形成不同的微观区域, 获得不同的界面, 产生不同的界面曲率, 可设计合成具有不同微观结构的超分子体系， 从而在分子水平上控制分子的自组装行为； 同时全氟链的引入所带来的氟效应能促进微观分离，稳定液晶相，并有利于复杂超分子体系的产生。

Synthesis and Mesophase Characterization of Block Molecules with Different Topologies

Synthesis and liquid crystalline behavior of three recently reported mesogenic block-molecules, namely polyhydroxy 1-benzoylaminopropane-2,3-diols I、star-shaped pentaerythritol tetrabenzoates II and calamitic bolaamphiphiles with lateral chains III which are constituted of anisometric block, amphiphilic block and alkyl or perfluorinated chains with different topologies are reviewed in this article. The palladium(0) catalyzed addition of perfluoroalkyliodides to the alkenes and palladium (0)catalyzed cross-coupling reaction are the key steps of the synthesis. By tailoring the scale between hydrophilic region and lipophilic region, smectic, columnar and cubic mesophases were observed in compounds I-F and II-F. By changing the length of the lateral chains, a series of new columnar phases and a non-conventional semctic phase were obtained in III-F. All the experimental results indicate, based on the competitive polyphilicity concept, micro-segregation of incompatible parts into different regions separated in space by interface, the occurred different interface curvature can lead to different mesophases with comlex supramolecular structures. The fluorophobic effect caused by the fluorinated chains can be used in combination with other incompatibilities to increase the micro-segregation and can stabilize the mesophase and also modifies the phase structure and leads to novel mesophases. By this way, the molecular self-assembly is controlled in molecular level.