液晶8CB轉動黏滯係數與溫度之關係

Abstract

我們利用同時測量具有自由表面液晶薄膜(FS)及不具有自由表面液晶薄 膜(HB)對磁場作用反應時間的方法得出液態晶體的旋轉黏滯係數。這種方 法的主要精神是將液態晶體旋轉時 ,亦造成流動的現象(backflow)考慮在 內。我們將測量此黏滯係數與溫度之關係，並與前人統計力學的理論預測 及其他利用忽視流動而測得之結果比較。 This thesis is to determine the temperature dependence of rotational viscosities for liquid crystal 4`-n-octyl-4- cyanobiphenyl(8CB) with consideration on the flow effect caused by rotation.We first measure and then compare the relaxation times under magnetic fields of films with and without a free surface at various temperatures.By these data, we can deduce the rotational viscosity as a function of temperature, and then compare with existing theories from statistical considerations. Since the relaxation times have to be measured under various magnetic fields and temperatures,we have automated our system by using personal computers to control the experimental conditions and to take the datd. By comparing the Osipov- Terentjev theory with our experimental results, the activation energy,mean-field potential of liquid crystal 8CB are obtained.