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    题名: 由3- 及4- 氫氧基- 苯甲酸衍生之不對稱液晶分子之合成及物性
    其它题名: Synthesis and properties of 3- and 4- hydroxy benzoic acids derivatives : unsymmetrical liquid crystals
    作者: 張哲誠;Chang, Che-cheng
    贡献者: 淡江大學化學學系碩士班
    余良杰;Yu, Liang-jye
    关键词: 液晶;螺旋結構;螺距反轉;旋光;膽固醇;彎曲形;helix;inversion;mesophase;chiral;pitch;liquid crystal
    日期: 2006
    上传时间: 2010-01-11 02:35:08 (UTC+8)
    摘要: 論文名稱:由3- 及4- 氫氧基- 苯甲酸衍生之不對稱液晶分子 頁數:93
    之合成及物性
    校系(所)組別: 淡江大學 化學系碩士班
    畢業時間既提要別:94學年度第2學期 碩士學位論文提要
    研究生:張哲誠 指導教授:余良杰
    論文提要內容:

    本研究的目的在探討由3-及4- 氫氧基苯甲酸所衍生之兩種不同構型的液晶分子及其取代基變化對液晶相的影響。主要分成兩部份,分別是3-氫氧基苯甲酸所衍生之不對稱彎曲行液晶分子;另一部份為4-氫氧基苯甲酸所衍生之旋光性棒狀液晶分子。

    第一部份為彎曲形液晶本系列為3- 氫氧基- 苯甲酸以酯基連接出來之1, 3 位置取代的不對稱彎曲形液晶分子。利用不同的合成方法,共合成四到六個苯環的化合物,兩側的尾端基為六至十六個碳的烷氧鏈,以不同碳數做變化,得到此一系列之化合物。在苯環數對液晶相的影響中,四個環的系列(4BCn),並沒有看到液晶相。到了五個環的系列(5BCn)還是沒有看到,但是文獻上,對稱的五個環對稱的系統有液晶相的生成所以推論本文中的五個苯環系列沒有液晶相,是因為不對稱的結構所導致;而Bn-5BC12卻看到液晶相N和SmC,當環數來到六個,則出現了一系列的彎曲形液晶相。所以推論5個苯環的系統,需要對稱的結構才能生成液晶相,而不對稱的系統因為其特殊的構造,所以在核心的構造中,需要更強的π-π作用力(π-π interaction),才能生成液晶相(如Bn5BC12)。而彎曲形液晶相(B phase)則需要更大的π-π作用力(如6B系列)。

    第二部份為旋光性液晶分子部份,本系列為乳酸衍生之條形液晶化合物,核心部份由四個苯環組成,以酯基為連接基;苯環兩側不對稱取代,一端為乳酸之衍生物,另一端為不同長度之碳鏈。乳酸部份有乳酸甲酯、乳酸乙酯及乳酸丁酯;另一邊則為碳數八至十六個碳的烷氧鏈。以兩邊不同碳數做變化,共有三個系列,乳酸側碳鏈長度(m)以數字簡寫為1、2、4,另一端烷氧鏈長度(n)分別以8、10、12、14、16代替,共合成1-n、2-n、3-n系列之化合物。本系列的化合物,最引人注意的地方,在於他有所謂的螺旋結構反轉(Helix Inversion)現象。在本篇論文所討論的三個系列中,皆可觀察到隨著尾端烷氧鏈的增長,會使得層相結構液晶更容易生成。在三個系列中,n=8 時,都只有一個液晶相(N*);到了n=10以後,便多出了SmC*;化合物1-14及1-16,甚至多了一個SmX*的液晶相出現。除了烷氧鏈,乳酸所接出來之烷氧基長度也會影響到層相結構;同樣的,也是烷氧鏈長度越長,越有助於層相結構的生成。旋光基對於液晶分子螺旋結構反轉的影響,只跟旋光基側的碳鏈長度有關,長度越長所需的反轉溫度越高;相對的,另一邊的烷氧基長碳鏈並不會影響到螺旋結構反轉的溫度。也就是說,旋光部份的取代基碳鏈增長,會使 inversion point 溫度上升。
    Synthesis and Properties of 3- and 4- Hydroxy Benzoic Acids Derivatives : Unsymmetrical Liquid Crystals
    Total Page:93
    Name of Institute: Graduate School of Chemistry Tamkang University
    Graduate Date: July, 2006 Degree Conferred: Master
    Name of Student: Che-Cheng Chang Advisor: Dr. Liang- Jye Yu

    Abstract:
    It can divide into 2 parts in this research. One is bent-shape liquid crystals, which are derivatives from 3-Hydroxy Benzoic Acid. Another is chiral rod-like liquid crystals which are derivatives from 4-Hydroxy Benzoic Acid. The mesophase behaviors were studied by optical polarizing microscopy, differential scanning calorimetry and powder X-ray diffraction.
    In the first part, according to different method, there are 4 to 6 benzene rings compounds and different alkoxy terminal chains to be synthesis. In 4B and 5B series, we can not observe liquid crystal phase, but in literature there are liquid crystal phase in the symmetry 5 rings system. Herein, we inference the absence of the liquid crystal phase is due to unsymmetrical structure of 5B series. In Bn-5BC12, we can observe N and SmC phase; In the 6 benzene rings system (6B series), there are series of liquid crystal phases. Consequently, we consider that in the 5 rings system need more symmetrical structure to receive liquid crystal phase; In the unsymmetrical system, because of its unusual structures, they need stronger π-π interaction to receive liquid crystal phase (5BC12), and more stronger π-π interaction to receive banana liquid crystal phase.
    The second part, we synthesis the chiral rod- like liquid crystals with lactate derivatives (m-n series). The core consists of 4 benzene rings, two wings substitutes by alkoxy chains and lactate derivatives. In all series of this part, exhibited I-N*-SmC*(-SmX*)-K phase sequence. The most noticeable place, lies in its “helix inversion”. As the n value (alkoxy chain) increase, the mesophase prefer to form smectic phase (SmC*, SmX*). Temperature of the helix inversion is occurred, called “inversion point ”. The inversion point depended on lactate-side alkoxy chain length. Methyl lactate derivative series, the inversion point is about 140℃; Ethyl lactate derivative series, the inversion point is about 180℃; but butyl lactate derivative series cannot observe helix inversion, we inference it occurs in 240℃, but at this temperature the compound already become isotropic. In opposite, the length of the alkoxy chain has no influence on inversion point.
    显示于类别:[化學學系暨研究所] 學位論文

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