探討非氟化及半氟化旋光材料對液晶相及其性質的影響

Study on the Effect of Non-fluorinated and Semi-fluorinated Chiral Materials on the Mesomorphic Phases and Properties

王怡蘋(Yi-Ping Wang)

指導教授 ： 吳勛隆

大同大學/工程學院/化學工程學系所/碩士(2010年)

摘要

以(R)-glycidyl methyl ether與烷鏈醇類和半氟化醇類在鹼性環境下反應合成出具有光學活性的醇類(R)-1-methoxy-3-propoxy-2-propanol和(R)-1-methoxy -3-(2,2,3,3,3-pentafluoropropoxy)-2-propanol。再以上述醇類合成三系列旋光性非氟化及半氟化材料，I(n=9, p=1, R=CH2CH2CH3), II(n=9-11, p=1, R=CH2CF2CF3)和III(n=9-11, p=2, R=CH2CF2CF3)，並探討非旋光末端烷鏈長度對誘電性液晶相的影響。液晶相及相轉移溫度的變化是經由偏光紋理圖及DSC所鑑定而得，而電流轉換行為及介電性質的量測則可進一步的鑑定誘電性液晶相的存在。此三系列旋光性化合物之探討結果如下:
旋光末端烷鏈為碳氫烷鏈之化合物I(n=9, p=1, R=CH2CH2CH3)不具任何液晶相，而在旋光末端烷鏈導入氟原子之半氟化旋光性化合物II(n=9-11, p=1, R=CH2CF2CF3)和III(n=9-11, p=2, R=CH2CF2CF3)則是有利於液晶相的生成。化合物II(n=9-11, p=1, R=CH2CF2CF3)具有SmA*相，其中化合物II(n=11, p=1, R=CH2CF2CF3)則是多了未鑑別的誘電性SmX*相，而化合物III(n=9-11, p=2, R=CH2CF2CF3)則是擁有SmA*相和誘電性SmC*相。化合物III(n=9-11, p=2, R=CH2CF2CF3)之結果顯示非旋光末端烷鏈的增長有利於層相液晶(SmC*)的生成。
將單苯環之硬核結構延伸至雙苯環可發現化合物的熔點，澄清點，液晶相之熱穩定性皆會上升，並有利於誘電性液晶相(SmC*)和雙向性液晶相的生成。
硬核結構為NaCOOPhPh的化合物III(n=9-11, p=2, R=CH2CF2CF3)與硬核結構為PhPhCOONa的化合物MMHEmPBN (m=9-11)之比較結果顯示前者不利於反誘電性液晶相(SmCA*)的生成。

化合物III(n=9-11, p=2, R=CH2CF2CF3)之誘電性液晶相(SmC*)的物理性質量測結果顯示其自發性極化值與非旋光末端烷鏈長度無明顯規則性，而在傾斜角的部分則是會因非旋光末端烷鏈的增長而上升。

關鍵字

非半氟化液晶 ； 半氟化旋光性液晶 ； 誘電性液晶相 ； 光電性質

並列摘要

Optically active alcohols, (R)-1-methoxy-3-propoxy-2-propanol and (R)-1-methoxy-3-(2,2,3,3,3-pentafluoropropoxy)-2-propanol, were designed and synthesized by the treatment of (R)-glycidyl methyl ether with non-fluorinated and semi-fluorinated alchols under basic condition. Three novel homologous series of chiral non-fluorinated and semi-fluorinated materials, I(n=9, p=1, R=CH2CH2CH3), II(n=9-11, p=1, R=CH2CF2CF3) and III(n=9-11, p=2, R=CH2CF2CF3), derived from these alcohols, were than synthesized for the investigation concerning the effect of the non-fluorinated and semi-fluorinated at the chiral group of the molecule on the formation of SmC* phase. The mesomorphic phases and their corresponding transition temperatures were primarily characterized by the microscopic textures and DSC thermograms, and the ferroelectric phase was further identified by the measurements of electric switching behavior and dielectric constant ε'.
The results obtained from the study of three series of chiral materials, I(n=9, p=1, R=CH2CH2CH3), II(n=9-11, p=1, R=CH2CF2CF3) and III(n=9-11, p=2, R=CH2CF2CF3) can be summarized as follows:
Compound with non-fluorinated alkyl chain have no mesomorphic phase, but the compounds with semi-fluorinated alkyl chain promote the formation of mesomorphic phase. Compounds II(n=9-11, p=1, R=CH2CF2CF3) possess SmA* phase, compound II(n=11, p=1, R=CH2CF2CF3) possess SmA* and an unidentified ferroelectric SmX* phase, and the compounds III(n=9-11, p=2, R=CH2CF2CF3) possess SmA* and ferroelectric SmC* phases. The extension of achiral alkanes increase from H(CH2)9O-, H(CH2)10O- to H(CH2)11O- resulted in an enhancement of the stability of mesophases, especially, the SmC* phase.
Extending phenyl ring to biphenyl ring in the core of the molecules could result in increasing melting point, clear point, thermal stability of mesophases, the formation of ferroelectric SmC* phase and enantiotropic mesophase.
Compounds with the core structure of NaCOOPhPh suppress the formation of antiferroelectric SmCA* phase as compared to the compounds with the core structure of PhPhCOONa where SmCA* is formed.
The physical properties of the chiral materials in ferroelectric SmC* phase of compounds III(n=9-11, p=2, R=CH2CF2CF3) were also measured. The magnitudes of maximum Ps values are in the range of 63.47-92.08 nC/cm2,, and have no significant correlation to achiral alkyl chain length. The magnitudes of apparent tilt angle (θ) values are in the range of 25.3° to 34.3°, and are increased with achiral alkyl chain length from nonyloxy group to undecyloxy group.

並列關鍵字

non semiflurinated liquid crystal ； semi-fluorinated chiral liquid crystal ； ferroelectric phase ； electro-optical property

參考文獻

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