臺灣博碩士論文加值系統

本研究所探討的液晶衍生物之剛硬核部分，是以四個苯環所組成。苯環與苯環之間以三個酯基官能基在對位的方向連接而成。當柔軟的烷氧鏈接上最外端兩個苯環的對位時，就形成典型的條形液晶，此類液晶分子具有大範圍的液晶相。而當一端的烷氧鏈以間位連接苯環時，可形成曲棍球棍形（彎曲形）液晶分子:Cn-m-Cm，此類液晶分子除了具有N、SmA以及SmC的液晶相之外還具有anticlinic SmC(SmCA)液晶相。
在分子結構中變化對位以及間位的碳氫鏈（Cm,Cn）長度，來研究對液晶相的影響時，可發現在較短的間位碳氫鏈衍成物易生成SmCA液晶相：當n=4時，m的長度由7變化到14皆可生成SmCA液晶相，當n=12時，m的長度在相同的變化下，皆無法觀察到SmCA液晶相。
此外在芳香環的部分也有進行下列相關衍生物的變化：(1)在最外端苯環的鄰位上加入側取代基-甲氧基：Cn-ms-Cm; (2)改變其中一個酯基連接基的方向Cn-mA-Cm; (3)將四個苯環減少一個苯環Cn-m-CmBA。上述的三類相關的衍生物皆無法生成SmCA液晶相。
Cn-m-Cm中的間位烷氧鏈以乳酸乙酯取代時可得曲棍球棍形旋光性液晶分子,Le-m-Cm。當m=8和10時，其液晶相序列為I2-I1-N*-TGBA-SmA。當m=12 和14，其液晶相序列為 I2-I1-N*-UTGBC 。此系列分子皆可發現特別的澄清相-澄清相的相轉移，此外本系列也會生成TGB相，表示曲棍球棍形旋光性液晶分子相較於條形旋光分子衍生物具有較強的螺旋扭力。
本實驗利用偏光顯微鏡、熱示差掃瞄分析儀、粉末X光繞射以及電場效應來獲得相關實驗數據。

A rigid core consisting of four phenyl rings connected by three ester functional groups at the para-positions has been used for making mesogenic derivatives. Typical calamitic mesogen with wide mesophase range is obtained when the flexible alkyloxy chains are attached at the para-positions of the ending rings. A hockey stick, or bent, shaped molecule is obtained when one of the alkyloxy chains is connected at the meta-position, Cn-m-Cm, and results in formation of anticlinic Smectic C (SmCA) in addition to SmC, SmA and N phases.
The mesophase-molecular structure relationship has been studied by varying the length of both the meta- and para-hydrocarbon chains, Cn and Cm, respectively. Occurrence of SmCA is more favorable for derivatives having shorter meta-chains: for n=4, SmCA phases are observed for derivatives with m=7 to 14, and for n=12 no SmCA phase is observed with the same m values.
Variation of the aromatic core is also conducted: (1) attach a methoxy group at the ortha-position of the ending ring, Cn-ms-Cm; (2) reverse the direction of one of the ester linking groups, Cn-mA-Cm; (3) remove one of the rings, Cn-m-CmBA. Derivatives obtained with these modifications exhibit no SmCA phase.
Chiral mesogens are obtained by replacing the aliphatic chain of the meta- position of Cn-m-Cm with ethyl lactate. Mesophase sequences observed are I2-I1-N*-TGBA-SmA for derivatives having m=8 and 10, and I2-I1-N*-UTGBC for m=12 and 14. Peculiar phase transition of iso to iso is observed for all these derivatives, along with the occurrence of TGB indicate that the twisting power is stronger for the hockey stick molecules as compared to the rod-like analogues.
The present study is carried out by optical polarizing microscopy, differential scanning calorimetry, powder X-ray diffraction and electric-field effect.

第一章 前言--------------------------------1
1. 鐵電性液晶----------------------------1
2. 反鐵電性液晶分子---------------------10
3. 旋光向列相（Chiral nematic phase or chrosteric phase----19
4. Frustrated Phase----------------------20
5. 研究目的------------------------------23
第二章 合成與結構鑑定---------------------26
1. 使用儀器及廠牌--------------------27
2. 藥品名稱與廠牌 -------------------28
3. 流程------------------------------30
4. 合成步驟--------------------------35
5. 元素分析--------------------------42
第三章 結果與討論-------------------------46
1. 化合物之液晶相性質 -------------------46
1-1 系列1A--------------------------------46
1-2 系列1B-改變分子架構-------------------70
1-3 系列2B--------------------------------74
2. 化合物液晶相的比較與性質討論----------86
2-1 尾端基對液晶相的影響------------------86
2-2 分子結構對對液晶相的影響--------------93
2-3 分子在液晶相的排列--------------------97
2-4 混液晶--------------------------------101
2-5 系列2A與系列2B的比較------------------104
第四章 結論-------------------------------108
參考文獻------------------------------------110

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