由彎曲型分子形成盤狀液晶之探討

The formation of the columnar phase by bent-core molecules

郭依蓁(Yi-chen Kuo)

指導教授 ： 賴重光

國立中央大學/理學院/化學系/碩士(2007年)

摘要

本論文研究主要的方向在於探討香蕉型液晶的製備、液晶相、與結構排列，研究的方向主要是延伸易筑萱學姐所做的具彎曲型化合物。論文中所有的化合物都經過NMR、Mass及元素分析鑑定其純度及結構，並由DSC量測得到液晶的相轉變溫度與熱焓值。
探討此系列化合物的主要原因在於筑萱學姐所合成出一系列的香蕉型B6相液晶，而我主要在學姐所合成的結構末端延長連接基並且改變碳數，進而探討結構的改變對原本液晶相造成的影響與變化。除了在偏光顯微鏡下觀察到液晶相由B6相變成盤狀液晶外，液晶相溫度範圍也拉長了約三十度左右，澄清點溫度也隨著上升。而此論文主要的方向便是在探討改變結構後，對分子所造成的液晶相性質之影響。
此系列分成兩個部分；第一部份主要是增加連接基後液晶相變化的探討，第二部分則是置換氫原子在可能產生分子內與分子間氫鍵的位置上，並與第一部份做比較，發現此部分某些化合物轉變成Smectic相，且伴隨著氫鍵的消失，澄清點溫度也跟著下降約二十五度C左右。因此結果得以確定分子間與分子內氫鍵對分子的排列以及液晶相確實會產生不可忽略的影響。

關鍵字

分子間氫鍵 ； 香蕉形液晶 ； 自組裝 ； 鐵電性質

並列摘要

This thesis describes the synthesis, characterization and mesomorphic properties of a series of organic compounds derived from N, N-(propan-2-ol)-bis(4-alkoxysalicylaldimine). These compounds are structurally considered as banana-shaped molecules or bent core (BC) molecules, and banana phases might be observed. All compounds prepared were characterized via 1H-NMR, 13C-NMR, mass spectroscopy, and elemental analysis. The mesophases were studied by polarized optical microscopy (POM), differential scanning calorimeter (DSC), and the structures of the mesophases were also confirmed by variable temperature X-ray diffraction experiments.
The results were compared with other similar compounds prepared previously in this group. A systematic change on the molecular structures was conducted to understand the effect of molecular structures on the mesomorphic behavior, in which compounds substituted with a variety of functional groups/substituents and/or terminal chain lengths were prepared and studied. A phase changed from B6 phase to columnar phase was obtained, and also the temperature range of the mesophase was increased by ca. 300C. The replacement of H atom at different position was found to induce the formation of smectic phases. In addition, the effect of possible hydrogen bonding induced to generate the mesophases was also investigated.

並列關鍵字

self-assembly ； H-bonding ； ferroelectricity ； banana LC

參考文獻

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