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URN etd-0728104-171439 Statistics This thesis had been viewed 2267 times. Download 922 times. Author Jui-Yang Chang Author's Email Address No Public. Department Chemical Engineering Year 2003 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 108 Title EFFECT OF MOLECULAR STRUCTURE ON THE STABILTY OF TGB PHASE AND MESOMORPHIC PROPERTIES OF THE CHIRAL LIQUID CRYSTALS Keyword TGB phase LIQUID CRYSTALS LIQUID CRYSTALS TGB phase Abstract ABSTRACT
From the results of recent paper, there are many factors effect the TGB phase formation such as steric, linking group and swallow tail structure. The purpose of this research is apt for a better understanding the relationship between molecular structure and TGB phase formation.
Four homologous series of chiral materials with methleneoxy linking group, alkyl (S)-2-(6-(4-(4´-alkoxyphenyl)benzyloxy)-2-naphthyl)propionates, SnH-m, and one homologous series of chiral materials with deuterated methleneoxy linking group, d2-3-ethylbutyl (S)-2-(6-(4-(4´-alkoxyphenyl)benzyloxy)-2-naphthyl)propionates, S2D-m , derived from (S)-2-(6-methoxy-2-naphthyl)-propionic acid, were designed, synthesized and investigated on the structure property relationship in the chiral liquid crystals.
The target compounds were independently modified by the linking group, length of terminal chain and chiral chain. Most of the compounds showed TGBA* phase. Both materials of S1H-m and S3H-m exhibited a wide temperature range of TGB phases and the temperature ranges of TGBC* and SmC* phase were mainly increasing with increasing terminal alkyl chain. Furthermore, when deuterium substituted for hydrogen atoms at the methyleneoxy linking group, in S2D-m the N* phase was disappeared and a direct Iso-TGBA* phase transition formed.
The magnitudes of spontaneous polarization of the ferroelectric SmC* phase were measured in a 5µm homogeneously aligned cell by the surface stabilized geometry. The largest Ps values of SnX-m were from 15nC/cm2 to 41 nC/cm2 and have no relation to the terminal alkyl chain.
In a conclusion, the results from above indicate that the linking group, swallow-tail structure and length of alkyl chain indeed have the significant effect on the incidence and stability of TGB phase. The systematic studies provide systematic evidences that the structure effect on the formation of the TGB phase.
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