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URN etd-0813112-152206 Statistics This thesis had been viewed 1703 times. Download 187 times. Author Ching-Chung Hsu Author's Email Address No Public. Department Chemical Engineering Year 2011 Semester 2 Degree Master Type of Document Master's Thesis Language Chinese&English Page Count 170 Title Study on the Synthesis and Mesogenic Properties of Salicyaldimine Derivatives with a Terminal (R)-2-Octyloxy Group Keyword Salicyaldimine Salicyaldimine Abstract This study isdivided into two parts, the first part we synthesized six series of new chiral salicylaldimine liquid crystal materials by introducing a terminal (R)-2-octyloxyl tail into various rigid core and changing the alkyl achiral alkyl chain length (n) to investigate their the mesogenic properties.
The mesogenic phases and their corresponding transition temperatures were primarily characterized by the microscopic textures and DSC thermograms. The six novel homologous series of chiral materials:
The results of the first series showed that compounds I (n=8-16) exhibit the mesophases sequence of N*-TGBA*-SmA*-SmCA*, Compounds I (n=5-7) exhibit a stable frustrated BPI phase and compound I (n=7) possesses the widest temperature range of the BPI phase (3.6 °C).
The result of the second series showed that compound II (n=6-8) exhibit the mesophases sequence of BPI-N*-SmA*-SmCA*, and compound II (n=6) possesses the widest temperature range of the BPI phase (2.5°C). SmCA* phase disappeared when the achiral alkyl chain length n=5. It is apparent that the achiral alkyl chain length (n) is too short to the formation of the SmCA* phase. When chlorine atom is incorporated into the phenyl ring next to the chiral group, one of stable frustrated phase, TGBA* is suppressed. Furthermore, the thermal stability of N* phase is decreased and the clearing point is declined about 20°C. However, the temperature range of Smectic phase is extended.
The third series of compounds III (n=5-8) shows the similar cooling sequence the second ones. Additionally similar to the second series, SmCA* phase disappeared when the achiral alkyl chain length n=5.
The fourth series of compound IV (n=6) exhibits the mesophases sequence of N*-SmA*-SmCA*, and SmCA*phase is narrow (2°C). Similar to the second series, the achiral alkyl chain length (n) of compound IV (n=6) is too short to the formation of the SmCA* phase. However, the rigid core extended to biphenyl ring could lead to clearing point raising to 250 °C.
The fifth series compounds V (n=11-14) in which the salicylaldimine core with primary alkyl amine exhibit the mesophases sequence of BPI-N*-SmA*-SmCA* and the clearing point descending to 125°C. In addition, ompound V (n=14) possesses the widest temperature range of the BPI phase (3.4 °C) in this series.
The sixth series of compounds in which the salicylaldimine core with primary alkyl amine and the rigid core is replaced by naphthalene have no mesogenic phases.
The second part of the works was to investigate whether the binary mixture of the blue phase materials could enhance the thermal stability of the blue phase. Thus, binary mixtures I (n=16) and TNLC3, V (n=12) and TNLC3, V (n=12) and 5CB with the weight percentage ratios of 100/0, 75/25, 50/50, 25/75, 0/100 of the compounds were prepared for the investigation. The results of binary mixtures of the blue phase materials also indicate that the enhancement of temperature range of blue phase by the mixing method is not feasible.
Advisor Committee Chun-Cheng Huang - advisor
Files Date of Defense 2012-07-20 Date of Submission 2012-08-16