液晶5CB旋轉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。量出了考慮backflow效應影響 之黏滯係數.與Osipov-Terentjev 化能,平均場位能.平均場位能為1.8kTc 比Maier-Saupe理論中的4.5kTc來的低. The rotational viscosity versus temperature relation for liquid 4`-n-pentyl-4cyanobiphenyl(5CB)is determined from the relaxation of 5CB under magnetic field.The appartus and data acquisition are with personal computers. The rotational viscosity of liquid crystal(5CB)is determined with consideration on the flow effect caused by rotation.We first and then compare the relaxation times under magnetic fields of with and without a free surface at various temperatures.By these we can deduce the rotational viscosity as a function of and then compare with existing theories from statistical Since the relaxation times have to be measured under various fields and temperatures,we have automated our system by using computers to control the experimental conditions and to take the The computer control method is also presented in this thesis. By comparing the Osipov-Terentjev theory with our experimental the activation energy,mean-field potential of liquid crystal 5CB obtained.To get reasonable alfa3,the mean- field coupling constant is about 1.8kTc,which is somewhat lower than the Maier-Saupe value of 4.5kTc.