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URN etd-0728104-111639 Statistics This thesis had been viewed 2125 times. Download 594 times. Author Hsiu-Nien Hsu Author's Email Address email@example.com Department Chemical Engineering Year 2003 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 72 Title Synthesis and Electro-Optical Properties of New Chiral Liquid Crystal Derived from (S)-Lactic Acid with the Lateral 2-Fluoro Substitution at Phenyl Ring Keyword V Shap Switching Lateral Substitution Ferroelectric Liquid Crystal Chiral Liquid Crystal (S)-Lactic Acid (S)-Lactic Acid Chiral Liquid Crystal Ferroelectric Liquid Crystal Lateral Substitution V Shap Switching Abstract The primary of this research work was an attempt to elucidate the correlation between structure and property in the chiral smectic liquid crystal. A homologous series of chiral materials derived from (S)-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 (i) the nonchiral peripheral methylene chain length ‘m’, (ii) the chiral tailed ether alkyl chain length ‘n’ and (iii) lateral 2-fluoro substitution in the core.
Chiral materials of three series I (m=8~12), II (m=8~12), and III (m=8~12), displayed enantiotropic mesophases of the SmA* and SmC* phases. (i)With the increasing nonchiral methylene chain lengths ‘m’, the temperature range of the mesophase decreases. It says that the clearing point decreases and the crystal point increases. (ii) When the chiral tailed ether alkyl chain length ‘n’ increase, the clearing point and crystal point decreases. (iii) The materials with lateral 2-fluoro substitutents in the phenyl ring of core could depress the formation of mesophase, lowering the transition temperature, melting point, clearing point and Ps values.
The electro-optical response in the series of chiral materials in the SmC* phase displayed typical ferroelectric hysteresis loop or hysteresis-free, V-shaped switching property upon various applied frequencies and temperatures. The maximum Ps values of I（m=8~10）, II（m=8~10）, III（m=8~10）vary form 19.89~43.93 nC/cm2. The variations of peripheral chain length ‘m’ in the tree series of compounds, have no remarkable effect on switching behavior in the SmC* phase.
In conclusion, the results indicated that the chiral tailed ether alkyl chain materials derived from (S)-lactic acid with the lateral 2-fluoro substitution in the phenyl ring of core are favorable for the formation of the wide temperature range of the ferroelectric phase. V-shaped switching behaviors appear in the SmC* phase of the chiral materials of the three series. This finding may provide a new way of assessing the nature of the V-shaped switching for display application.
Advisor Committee Shune-Long Wu - advisor
Hong-Cheu Lin - co-chair
Jin-Jei Wu - co-chair
Files Date of Defense 2004-06-10 Date of Submission 2004-07-28