Synthesis and Properties of New Liquid Crystal Derived From Chiral (L)-Lactic Acid with Swallow-Tailed Group
| Autor: | Ray-Beam Chen, 陳瑞斌 |
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| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 The primary of this research work was an attempt to elucidate the structure-property correlation in the chiral smectic liquid crystal. A homologous series of chiral materials derived from (L)-lactic acid has been successfully synthesized and the structures-property relationship investigated in the chiral liquid crystal system. The target compounds were modified independently by the (i) ester linkage between chiral lactate and core structures, (ii) ether linkage between chiral lactate and core structures, (iii) ether linkage between chiral lactate and different core structures for the study. Chiral swallow-tailed materials,Ⅰ(n=1,2), displayed enantiotropic mesophase of the SmA* and SmC* phase. The electro-optical response in this series of chiral materials in the SmC* phase displayed typical ferroelectric hystersis loop, abnormal hysteresis, and hysteresis-free catch V-shaped switching property upon verious applied frequency. The variations of peripheral chain length, m, in this series of compound, have no remarkable effect on spontaneous polarization, dielectric property and switching behavior in the SmC* phase. Chiral swallow-tailed materials, Ⅱ(m,n; m=0,1, n=1,2), displayed enantiotropic mesophase of the SmA* and SmC* phase. In addition, when the methylene group (m) is decreased from 1 to 0 the higher disordered liquid crystalline phase disappeared, i.e., the blue phase BP, chiral nematic N* phase and Twist grain boundary TGBA* phase.The Ps values for compounds are in the order of the linking group (m). When the methylene group m=1 possesses higher Ps values then the m=0. The electro-optical response in this series of chiral materials in the SmC* phase displayed W-shaped switching, the inverse W-shaped switching, and hysteresis-free catch V-shaped switching property upon verious applied frequency. Chiral swallow-tailed materials, Ⅲ(m,n; m=0,1, n=1,2), displayed enantiotropic mesophase of the SmA* and SmC* phase. When the linking group (m) is 1 series have the same phase of the Iso, N*, TGBA*, SmA*, SmC*, amd Cr. phases. When the methylene group m=0 possesses chiral nematic phase N* only. W-shaped switching was observed at compounds Ⅲ (m,n; m=1, n=1,2) possessing SmC* phase at appropriate temperatures and frequencies. In conclusion, the results indicated that the chiral swallow-tailed materials derived from (L)-lactic acid are favorable for the formation of the ferroelectric phase. V-shaped switching behavior achieved in the SmC* phase at chiral compound Ⅰ(n=1), Ⅱ(m,n; m=1, n=1,2). This finding may provide a new way of assessing the nature of V-shaped switching for display application. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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