末端含旋光(R)-2-辛烷基之水楊醛亞胺之衍生物合成與液晶性質探討

Study on the Synthesis and Mesogenic Properties of Salicyaldimine Derivatives with a Terminal (R)-2-Octyloxy Group

徐慶鐘(Ching-Chung Hsu)

指導教授 ： 黃俊誠

大同大學/工程學院/化學工程學系所/碩士(2012年)

摘要

本研究分為兩部分，第一部分將旋光(R)-2-辛烷基導入水楊醛亞胺(salicylaldimine)衍生物的末端為主，藉由改變硬核結構及非旋光烷鏈長度，共合成出六系列新型旋光液晶材料，並觀察其對液晶相的影響。
　　藉由偏光紋理圖及DSC 的鑑定可分別得知液晶相及相轉移溫度的變化。六個系列液晶化合物其結構如下:
實驗結果顯示：
第一系列的化合物中，非旋光烷鏈I(n=8-14)時，在降溫時呈現出N*-TGBA*-SmA*-SmCA*的液晶相順序。其中在非旋光烷鏈I(n=5-7)時，增加了BPI的液晶相，其中I(n=7)時有最廣的藍相範圍(3.6 °C)。
　　第二系列在非旋光烷鏈II(n=6-8)時，在降溫時呈現BPI-N*-SmA*-SmCA*液晶相順序，其中II(n=6)時有最廣的藍相範圍(2.5°C)。非旋光烷鏈II(n=5)時，SmCA*液晶相消失，證實了非旋光烷鏈(n)長度太短時，不利於SmCA*液晶相之生成。在第二系列中硬核結構導入氯的取代基後，發現澄清點下降約20°C，TGBA*液晶相消失且N*液晶相範圍縮小，SmA*液晶相範圍增加。
　　第三系列的化合物中，III(n=6-8)在降溫時呈現出N*-SmA*-SmCA*液晶相順序，與第二系列化合物相同，在非旋光烷鏈III(n=5)時，SmCA*液晶相消失。
　　第四系列化合物IV(n=6)呈現出N*-SmA*-SmCA*液晶相順序，SmCA*溫度範圍很窄(約2°C)，非旋光烷鏈太短不利於由於SmCA*液晶相生成。然而在第四系列中，若將硬核改為雙苯環時，會導致澄清點升高至250°C。
　　第五系列化合物，我們將水楊醛亞胺右半邊的苯胺(aniline)改為不同碳數的一級胺(amine)形成系列V，則澄清點會下降至125°C，V(n=11-14)降溫過程皆呈現出BPI-N*-SmA*-SmCA*的液晶相順序，其中V(n=14)時有最廣的藍相範圍(3.4 °C)。
　　第六系列將硬核改為奈環，同第五系列將苯胺改為一級胺時則不具有液晶相生成。
　　第二部分的研究是探討混合液晶對於藍相(BP)液晶的穩定性影響。以
I (n=16)/TNLC3, V (n=12)/TNLC3以及V (n=12)/5CB的兩混合液晶材料為主要的觀察與探討。將化合物依不同重量百分比的比例混合(100/0,75/25,50/50, 25/75,0/100)觀察藍相(BP)液晶相溫度範圍的變化。在混合液晶材料實驗中，結果顯示混合藍相(BP)液晶材料對於藍相(BP)液晶的溫度範圍並沒有顯著的影響。

關鍵字

水楊醛亞胺

並列摘要

This study isdivided into two parts, the first part we synthesized six series of new chiral salicylaldimine liquid crystal materials by introducing a terminal (R)-2-octyloxyl tail into various rigid core and changing the alkyl achiral alkyl chain length (n) to investigate their the mesogenic properties.
The mesogenic phases and their corresponding transition temperatures were primarily characterized by the microscopic textures and DSC thermograms. The six novel homologous series of chiral materials:
The results of the first series showed that compounds I (n=8-16) exhibit the mesophases sequence of N*-TGBA*-SmA*-SmCA*, Compounds I (n=5-7) exhibit a stable frustrated BPI phase and compound I (n=7) possesses the widest temperature range of the BPI phase (3.6 °C).

The result of the second series showed that compound II (n=6-8) exhibit the mesophases sequence of BPI-N*-SmA*-SmCA*, and compound II (n=6) possesses the widest temperature range of the BPI phase (2.5°C). SmCA* phase disappeared when the achiral alkyl chain length n=5. It is apparent that the achiral alkyl chain length (n) is too short to the formation of the SmCA* phase. When chlorine atom is incorporated into the phenyl ring next to the chiral group, one of stable frustrated phase, TGBA* is suppressed. Furthermore, the thermal stability of N* phase is decreased and the clearing point is declined about 20°C. However, the temperature range of Smectic phase is extended.
The third series of compounds III (n=5-8) shows the similar cooling sequence the second ones. Additionally similar to the second series, SmCA* phase disappeared when the achiral alkyl chain length n=5.
The fourth series of compound IV (n=6) exhibits the mesophases sequence of N*-SmA*-SmCA*, and SmCA*phase is narrow (2°C). Similar to the second series, the achiral alkyl chain length (n) of compound IV (n=6) is too short to the formation of the SmCA* phase. However, the rigid core extended to biphenyl ring could lead to clearing point raising to 250 °C.
The fifth series compounds V (n=11-14) in which the salicylaldimine core with primary alkyl amine exhibit the mesophases sequence of BPI-N*-SmA*-SmCA* and the clearing point descending to 125°C. In addition, ompound V (n=14) possesses the widest temperature range of the BPI phase (3.4 °C) in this series.
The sixth series of compounds in which the salicylaldimine core with primary alkyl amine and the rigid core is replaced by naphthalene have no mesogenic phases.

The second part of the works was to investigate whether the binary mixture of the blue phase materials could enhance the thermal stability of the blue phase. Thus, binary mixtures I (n=16) and TNLC3, V (n=12) and TNLC3, V (n=12) and 5CB with the weight percentage ratios of 100/0, 75/25, 50/50, 25/75, 0/100 of the compounds were prepared for the investigation. The results of binary mixtures of the blue phase materials also indicate that the enhancement of temperature range of blue phase by the mixing method is not feasible.

並列關鍵字

Salicyaldimine

參考文獻

[8] L.J. Yu, H. Lee, C.S. Bak, M.M. Labes. Phys. Rev. Lett., 36, 388 (1976).

[9] N.A. Clark, S.T. Lagerwall. Appl. Phys. Lett., 36, 899 (1980).

Y.S. Negi, T. Hagiwara, I. Kawamura, H. Orihara, Y. Ishibahsi. Jpn. Display

[12] F. Reinitzer. Monatsh. Chem., 9, 421 (1888).

[13] Z. Lehmann. Phys. Chem., 4, 462 (1889).