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URN etd-0720105-155529 Statistics This thesis had been viewed 2077 times. Download 974 times. Author Ming-Pan Kao Author's Email Address No Public. Department Chemical Engineering Year 2004 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 103 Title Synthesis and Electro-Optical Properties of Naphthyl Benzoate Liquid Crystals Derived from Semi-fluorinated and Non-fluorinated Alkanes Keyword naphthyl benzoate ferroelectric antiferroelectric antiferroelectric ferroelectric naphthyl benzoate Abstract The purpose of this research work was an attempt to the structure-property correlation in the chiral liquid crystal materials. Three series chiral liquid crystal materials which have naphthoates were designed and synthesized for investigating the correlation between the chemical structure of chiral tails and mesomorphic properties.
The mesophase and their corresponding transition temperatures of the liquid crystal materials were identified by the polarizing microscopic texture, DSC carlorimetry and the electro-optical measurements The antiferroelectric phase was further characterized by the polarizing microscopic texture, the switching current behavior and the electro-optical response.
Compounds, I(m=7、9、11; n=2) exhibit a phase sequence of Iso.-SmA*-SmC*-Cr. in cooling process; compounds, I(m=8、10、12; n=2) exhibit a phase sequence of Iso.-SmA*-SmC*-SmCA*-Cr. in cooling process. All compounds of I(m=7~12, n=2) exhibit enantiotropic SmA* phase and SmC* phase, compounds of I(m=8、10、12, n=2) exhibit an additional enantiotropic SmCA* phase.
Compounds, II(m=7、9、11、12; n=1) exhibit a phase sequence of Iso.-SmA*-SmC*-Cr. in cooling process; compounds, II(m=8、10; n=1) exhibit a phase sequence of Iso.-SmA*-SmCA*-Cr. in cooling process. All compounds of II(m=7~12, n=2)
exhibit enantiotropic SmA* phase. With exception of II(m=8、10; n=1),the rest of the materials, exhibit enantiotropic SmC* phase whereas the compounds, II(m=8、10; n=1) exhibit enantiotropic SmCA* phase.
Compounds, III(m=7~12; n=1) exhibit a phase sequence of Iso.-SmA*-SmC*-Cr. in cooling process. All compounds of III(m=7~12; n=1) exhibit enantiotropic SmA* phase and monotropic SmC* phase.
The thermal stabilities of mesophase for the semi-perfluorinated compounds, I(m=7~12, n=2) and II(m=7~12, n=1) decrease with increase in nonchiral terminal chain length, whereas the non-perfluorinated compounds, III(m=7~12, n=1) increase.
The phase transition temperature of SmC*-SmCA*, SmCA*-Cr. and the melting point of I(m=7~12, n=2), SmA*-SmCA*, SmCA*-Cr. and the melting point of II(m=7~12, n=1), and SmC*-Cr. and the melting point of III(m=7~12, n=1) decrease with increasing the nonchiral chain length. And the phase transition temperature of above materials appear an odd-even effect.
The maxinun Ps value of compounds, I(m=8~11, n=2), II(m=8~11, n=1), and III(m=8~11, n=1) are in a range of 76.7 to 87.6nC/cm2 , 64.5 to 69.5nC/cm2, and 6.4 to 9.1nC/cm2, respectively.
The maxinun tilt angle of compounds, I(m=8~11, n=2), II(m=8~11, n=1), and III(m=8~11, n=1) are in a range of 31°~41.5° , 25°~42°, 15.7°~26.5°, respectively.
Advisor Committee Shune-Long Wu - advisor
Chin-Tsou Kuo - co-chair
Jiunn-Yih Lee - co-chair
Files Date of Defense 2005-07-13 Date of Submission 2005-07-20