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URN etd-0626106-160723 Statistics This thesis had been viewed 2264 times. Download 1042 times. Author Ji-han Fan Author's Email Address No Public. Department Chemical Engineering Year 2005 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 119 Title Synthesis and Mesomorphic Properties of Novel Chiral Liquid Crystals Derived from (S)-2-(6-Methoxy-2-naphthyl)propionic Acid Keyword ferroelectric furstrated phase liquid crystal liquid crystal furstrated phase ferroelectric Abstract The purpose of this research works was an attempt to elucidate the effect of molecular structure on the stability of TGB phase and mesomorphic properties of the chiral liquid crystals. A homologous series of chiral materials derived from (S)-2-(6-methoxy-2-naphthyl)propionic acid has been successfully synthesized. The target compounds were modified in dependently by (i) the chiral branch chain length ‘q’, (ii) the second chiral center and (iii) the nonchiral peripheral alkyl chain length ‘m’.
Compound ±S-C12-q (q=0) displayed mesophase of SmA*-SmC*, compound ±S-C12-q (q=1) exhibited the N*-TGBA*-TGBC*, and others compounds ±S-C12-q (q=2, 3) showed the phase sequence of N*-TGBA*-SmA*-SmC*. Compounds RS-Cm-1 (m-8-12) all exhibited the SmA* and SmC* phases, but at shorter alkyl chain compounds RS-Cm-1 (m=8, 9) displayed additional N* phase and compound RS-Cm-1 (m=8) displayed TGBA* phase. Compounds SS-Cm-1 (m=8-12) showed the mesophases sequence of N*-TGBA*-SmA*-SmC*. Compound SS-Cm-1 (m=10) displayed additional BPII and BPIII phases.
The maximum magnitudes of spontaneous polarization (Ps values) for the chiral materials ±S-C12-q (q=0-3), RS-Cm-1 (m=9-11) and SS-Cm-1 (m=9-11) were obtain in the range of 1.2-23nC/cm2 and the maximum optical tilt angle values of compounds ±S-C12-q (q=0-3), RS-Cm-1 (m=10-12) and SS-Cm-1 (m=10-12) were between 29-45o. The electro-optical response demonstrated that material ±S-C12-2 displayed thresholdless V-shaped switching in the SmC* phase.
In conclusion, the results indicated that the branched chain of the terminal group may help the TGB phase formation, and the (S, S)-isomers had better thermal stability of frustrated phase than (R, S)-isomers. The spontaneous polarization values of (S, S)-isomers were higher than (R, S)-isomers, and the (S, S)-isomers had higher optical tilt angles than (R, S)-isomer.
Advisor Committee Shune-long Wu - advisor
Chain-shu Hsu - co-chair
Chin-tTsou Kuo - co-chair
Hong-cheu Lin - co-chair
Files Date of Defense 2006-06-16 Date of Submission 2006-06-26