作者:Sayed Mir Sayed、Bao-Ping Lin、Hong Yang
DOI:10.1039/c6sm01019a
日期:——
A series of new columnar liquid crystals containing an adamantane central unit with its four bridgehead positions partially or fully decorated with different numbers (1–4) of 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups were designed and investigated carefully to explore the structure–property correlations. The molecular structures and mesomorphic properties of the DLCs were characterized by 1H-NMR, 13C-NMR, IR, UV-vis, POM, DSC and XRD. It was found that the mesophase symmetry and thermal stability were extremely dependent on the structures of the adamantane derivatives. No mesophase was observed for the 1-adamantanecarboxylic acid derivative ADLC1, while two different mesophases were observed for ADLC2, a 1,3-disubstituted derivative functionalized with two 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups at two symmetric bridgehead positions. At lower temperature ADLC2 exhibited a rectangular columnar phase, which switched to a square columnar phase possessing a wide temperature range. Similarly, a hexagonal columnar mesophase was observed for the bridgehead trisubstituted adamantane molecule ADLC3. Interestingly, the fully bridgehead-functionalized 1,3,5,7-tetrasubstituted adamantane compound ADLC4 completely lost liquid crystallinity.
一系列新的柱状液晶被设计和仔细研究,这些液晶包含一个带有不同数量(1-4)3,4,5-三(十二烷氧基)苯基氨基甲酸基团的四个桥头位置部分或完全修饰的金刚烷中心单元,以探索结构与性质之间的关系。这些DLC的分子结构和介质性质通过1H-NMR、13C-NMR、红外光谱、紫外-可见光谱、偏振光显微镜、差示扫描量热法和X射线衍射进行了表征。研究发现,介相的对称性和热稳定性极大程度上依赖于金刚烷衍生物的结构。对于1-金刚烷羧酸衍生物ADLC1未观察到介相,而在桥头对称位置引入两个3,4,5-三(十二烷氧基)苯基氨基甲酸基团的1,3-二取代衍生物ADLC2则观察到了两种不同的介相。在低温下,ADLC2表现出长方形柱状相,而在较宽的温度范围内则切换至方形柱状相。同样,在桥头三取代金刚烷分子ADLC3中观察到了六角柱状介相。有趣的是,完全修饰桥头的1,3,5,7-四取代金刚烷化合物ADLC4完全失去了液晶性。