Dielectric Spectra of Ferroelectric Liquid Crystals with various Chains moleculars And its effect under Magnetic Field

• Main Authors: Lin,Tang-Yu LIN, 林堂煜
• Other Authors: Fu,Chao-Ming
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/64748275007460605570

碩士 === 國立高雄師範大學 === 物理學系 === 93 === This thesis aims to study molecular dynamic behavior and electro-optical response of ferroelectric liquid crystals with various terminal chains molecular. In order to this purpose, the spontaneous polarization of FLCs was measured by utilizing Automated LC Property Tester. High precision LCR meters were applied to measure dielectric relaxation spectroscopy of FLCs; based on dielectric relaxation theory, the measured results were analyzed to discover dynamic behavior of liquid crystal molecules surrounded with alternating electromagnetic field. The electro-optical response was measured by home-built electro-optical measurement system. Based on the spontaneous polarization measurement, the spontaneous polarization of FLCs is correlated with the terminal chain molecular. The measurement of electro-optical response shows that the response time of FLC is correlated with spontaneous polarization and viscosity. The analysis of dielectric spectroscopy measurement has been discovered a novel relaxation mode on N* phase and SmA phase. In addition, an unknown liquid crystal phase was discovered on sample B and sample C. According to the spontaneous polarization that was not zero on the unknown liquid crystal phase, we can prove the unknown liquid crystal phase that is a smectic phase with tilt angle . The dielectric spectra measured under magnetic field showed that the Goldstone motion was enhanced among four samples during the study process. The measurement after removing the magnetic field was different with the result never applied magnetic field. The phenomenon of FLCs under magnetic field is meaningful.