液晶分子烷鏈長度與硬核結構的改變對藍相液晶生成的影響

Effect of Varying the Alkyl Chain Lengths and Core Structures of Liquid Crystal Molecules on the Formation of Blue Phases

陳威誠(Wei-Cheng Chen)

指導教授 ： 吳勛隆

大同大學/工程學院/化學工程學系所/碩士(2011年)

摘要

本研究是以(S)-propylene oxide為起始物合成三個系列的液晶化合物，藉由分子結構的改變，設計出具有高旋光度的藍相液晶材料，並探討(i) 非旋光末端烷鏈長度‘m’，(ii) 旋光烷鏈長度‘n’，(iii) 不同硬核結構由PhCOONa及PhCOOPhPh ，(iv) 具有醚基結構與不具醚基結構的非旋光烷鏈液晶相的生成，特別是藍相生成的影響，借以建立分子結構與藍相液晶相生成的關係。三系列液晶化合物其結構如下:
實驗結果顯示:化合物I(m=7, n=2)有出現BPII-N*-Cr. 的液晶相順序，化合物I(m=6-9, n=1)和I(m=6, 8, 9, n=2)有N*-Cr. 的液晶相順序，當I(m=7, n=2)時，具有寬廣的雙向性BPII液晶相。
第二系列的化合物是將硬核結構由PhCOONa改為PhCOOPhPh，結果顯示化合物II(m=8, n=1)具，有SmA*-Cr. 的液晶相順序，化合物II(m=7, n=5)具有BPI-N*-SmA*-Cr. 的液晶相順序，化合物II(m=6-9, n=4) 和II(m=8, n=5)時，則有BPII-BPI-N*-SmA*-Cr. 的液晶相順序。以上所合成的化合物都具有雙向性的BPII和BPI液晶相，當(m=7, n=4)到(m=8, n=4)和(m=9, n=4)的時候，BP 液晶相的溫度範圍會隨之增加。將旋光烷鏈長度(n)延長，BP 液晶相的溫度範圍會降低並且在 II(m=7, n=5)時，無BPII液晶相的生成。
第三系列化合物和第二系列化合物具有相同的旋光結構，差異性在於化合物III(n)是將非旋光末端烷鏈具有醚基結構改為不具醚基結構，結果顯示化合物III(n=1)時，有 SmA*-Cr. 的液晶相順序，III(n=2)時，有BPI-N*-Cr. 的液晶相順序，III(n=3, 4)時，有BPII-BPI-N*-Cr. 的液晶相順序，相較於化合物II(m, n)，III(n)藍相液晶相的溫度範圍升高。
總而言之，旋光材料中較短的旋光末端烷鏈(n=1-2)會抑制藍相的生成，較長的旋光末端烷鏈有助於藍相的生成。當硬核由PhCOONa改為PhCOOPhPh硬核結構時化合物澄清點上升以及藍相液晶溫度範圍也增加。而非旋光末端烷鏈增長時化合物澄清點上升，但藍相液晶溫度範圍並沒有隨之增加。非旋光烷鏈不含醚基比非旋光烷鏈含有醚基時澄清點下降但藍相液晶溫度範圍增加。三系列的化合物中，化合物II(m=9, n=4)有最寬廣的藍相液晶範圍(約3.9℃)，呈現BPI和BPII液晶相。

關鍵字

旋光性材料 ； 藍相 ； 膽固醇相

並列摘要

The primary research work of this study is an attempt to correlate the structure-property relationship of the formation of blue phases in chiral liquid crystals in terms of variation of the achiral alkyl chain length (m), chiral alkyl chain length (n), structure of the rigid core, and achiral alkyl chain length (m) without ether linkage in the chiral liquid crystal materials.
Thus, the optically active alcohols, 1-ethyloxy-2-propanol, 1-propyloxy-2-propanol, 1-butyloxy-2-propanol, 1-pentyloxy-2-propanol, 1-hexyloxy-2-propanol, were designed and synthesized by reacting (S)-propylene oxide with alkyl alcohols under basic condition. In consequence, three novel homologous series of chiral materials, (R)-6-(1-alkyloxy-2-propyl)naphth-2-yl 4-alkyloxybenzoate, I(m=6-9, n=1-2), (R)-4-(1-alkyloxy-2-propyl)biphenyl 4-alkyloxybenzoate, II(m=6-9, n=1, 4, 5), (R)-4-(1-alkyloxy-2-propyl)biphenyl 4-heptylbenzoate, III(n=1-4), derived from these alcohols were synthesized for the investigation of the effect of the achiral alkyl chain length (m), ether linking group, chiral tail alkyl chain length (n) and rigid core structures on the mesomorphic.
The mesomorphic phases and their corresponding transition temperatures were primarily characterized by the microscopic textures and DSC thermograms.
The results of compounds I(m, n) composed of the rigid core structure of PhCOONa and chiral group of optical activity 1-ethyloxy-2-propanol and 1-propyloxy-2-propanol, showed that compound I(m=6-9, n=1) and I(m=6, 8, 9, n=2) exhibits the mesophases sequence of N*-Cr., and the compound I(m=7, n=2) exhibits the mesophases sequence of BPII-N*-Cr.. With the exception of I(m=7, n=2) that exists the widest temperature range of enantiotropic BPII phase.
The results of compounds II(m=6-9, n=1, 4, 5) composed of the same chiral group but differed in the rigid core structure (PhCOOPhPh) as compounds I(m, n). The compound II(m=8, n=2) exhibits the mesophases sequence of SmA*-Cr., the compound II(m=7, n=5) exhibits the mesophases sequence of BPI-N*-SmA*-Cr., the compound II(m=6-9, n=4) and I(m=8, n=5) exhibits the mesophases sequence of BPII-BPI-N*-SmA*-Cr., The widest temperature range of BP phases for these compounds appeared at II(m=9, n=4).
The results of compound III(n=1-4), the composed of the same rigid core structure as compound II(m, n) but differed in the achiral group where a reducible ether linkage is introduced, the compounds III(n=1) exhibit the mesophases sequence of SmA*-Cr., the compounds III(n=2) exhibit the mesophases sequence of BPI-N*-Cr., the compounds III(n=3-4) exhibit the mesophases sequence of BPII-BPI-N*-Cr..
In general, the results of mesomorphic phases show that compounds with the short alkyl lengths (n=1-2) at chiral groups generally suppress the formation of BP phase, however, compounds with longer length (n=3-5) enhance the thermal stability of BP phase. The results also show that, when the rigid core structures of the molecules change from PhCOONa to PhCOOPhPh, the clear point is increased and the stability of blue phase is also increased. Moreover, when extending the alkyl length (m) of achiral tail, the clear point is increased but the thermal stability of blue phase display no significant difference. Compounds having achiral group without ether linkage between the core display lower clear point, and lower the thermal stability of blue phase as compared to the compounds having ether linkage between the core and achiral alkyl chain. Among these three series of chiral compounds, compound II(m=9, n=4) has the widest BP phase temperature range (cal. 3.9℃), where BPI and BPII formed.

並列關鍵字

cholesterol phase ； Blue phase ； Chiral material

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