| Summary: | 碩士 === 國立成功大學 === 化學學系 === 83 ===
A series of monomers containing biphenyl phenyl benzoate based mesogenic core with various lengths of oligo ( ethylene glycol) monomethyl ether as terminal group were synthesized. The structure and the thermodynamic properties of these compounds were investigated. The purpose of this work is to improve the thermal stability of these series of compounds. The purity, the thermotropic trasition temperature and the mesophase texture were studied by means of nuclear magnetic resonance spectroscopy, differential scanning calorimetry and optical polarized microscopy with a hot stage. All the monomers synthesized occur nematic mesophase. The decrease of melting point(Tm), isotropic transition temperature (Ti) and thermodynamic parameter with the increasing the lengths of alkenyloxy group were observed. Similar results were found for the decrease of melting point, isotropic transition temperature and thermodynamic parameter with the increasing lengths of the terminal group. With the increase of the number of phenyl rings of mesogenic group, the Tm and Ti values will also increase.
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