液晶電流變行為之研究

The Study of Electrorheological Behavior of Liquid Crystal

張佳揚(Chia-Yang Chang)

指導教授 ： 芮祥鵬

國立臺北科技大學/工程學院/有機高分子研究所/碩士(2005年)

摘要

本篇研究可以分成兩個部份，第一部份是關於液晶高分子的電流變效應，將聚（L-麩胺酸苯甲基酯）（PBLG）與二氧六圜（1.4-Dioxane）以18wt%配製，即可得到均相電流變流體，此液晶高分子具有沿著螺旋軸的永久偶極，被預期在直流電場下，可以得到電流變效應。本實驗使用同軸圓柱式流變儀（VT550），在不同電場強度、溫度與濃度下，觀察液晶高分子的黏度性質，其結果發現，當施加電場時黏度將有明顯的提升，亦即說明了分子間的活動，分子於兩電極板形成架橋結構，因而增加流體流動的阻力，使得黏度增加，而此現象只發生於異向性溶液中。此類的電流變效應，跟電場強度、溫度和濃度有關，可以藉由阿瑞尼斯（Arrhenius）方程式，計算流動活化能，進而展現出液晶高分子的
形態。
第二部份是關於向列相液晶5CB 7CB於電場作用下之流變性質，它的黏彈性質可以藉由微管式震盪流變儀（VE-SYSTEM）得到，我們找到此電流變行為同樣跟電場強度和溫度有關，在向列相溫度時，黏度與鬆弛時間隨著電場強度增加而增加，並趨於飽和，隨溫度增加而下降。而此5CB 7CB的動態黏彈性行
為可以完整以Maxwell模型加以模擬。

關鍵字

電流變效應 ； 電流變流體 ； 聚（L-麩胺酸苯甲基酯） ； 液晶高分子

並列摘要

This study consists of two parts. The first part focuses on the electrorheological effect of homogeneous electrorheological fluid in regard to the liquid crystalline polymer, PBLG Poly(γ-benzyl L-glutamate), in 1.4-Dioxane with a concentration of 18wt%. The liquid crystalline polymer with the permanent dipole along the helix axis is found to show electrorheological effect under DC field. This study employed a concentric cylinder viscometer, VT550, to investigate the viscosities of liquid crystalline polymer under various conditions which include the changes in electric field strength, temperature, and concentration. An apparent increase in viscosity was found when the electric field was applied. It was attributed to the formations of bridge structures along the electric field resulted from a consequence of the interaction between the molecules. The flow resistance was consequently enhanced. Such an ER effect was heavily dependent on the applied electric field strength, the concentrations, and the system temperatures. The activation energies of viscosity can be calculated by Arrhenius equation and was found to be highly sensitive to the anisotropy of the LCP materials.

The second part is investigated the rheological properties of liquid crystal compounds, 5CB 7CB, subjected into an electric field. The viscoelastic properties of the two liquid crystals were measured by the oscillatory flow viscoelasticity analyzer, VE-SYSTEM. Similar to the previous study, the electrorheological behavior was also dependent on the electric field strengths and temperatures. Within the temperature range of a nematic phase, the viscosity and relaxation time increase with amplitude of the electric field, but decrease with the temperature. The Maxwell model was found to be able to depict the dynamic viscoelastic behavior of 5CB 7CB
perfectly.

並列關鍵字

electrorheological effect ； electrorheological fluid ； Poly(γ-benzyl L-glutamate) ； liquid crystalline polymer

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