液晶分子及液晶高分子之電流變行為研究

Electrorheological Behavior of Nematic Liquid Crystal and Liquid Crystalline Copolymer

吳姿燕(Tzu-Yen Wu)

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(2009年)

摘要

本研究可分為兩個部分，第一部分是關於電流變效應在液晶材料上等研究探討，此實驗是利用酯交換反應，將Poly(γ-benzyl L-glutamate) (簡稱PBLG)接上正十二烷基之長碳鏈，將此種液向型液晶高分子改質成熱塑性液晶高分子Poly(γ-benzyl L-glutamate-co-γ-dodecyl L-glutamate) (簡稱PBLG – PDLG)，且經由1H-NMR 證實此化合物結構為正確，以偏光顯微鏡之紋理圖來確定液晶材料相變化，其液晶相之溫度介於70~150°C 之間，再使用平板式流變儀( Physica MCR 301 )，在不同電場強度下觀察液晶高分子的黏度性質，其結果發現，當施加電場時黏度有明顯的提升，說明了液晶分子間的活動，分子偶極被電場所影響間接影響了液晶分子間內的結構排序，增加液晶分子活動的阻力，使黏度提高。
第二部分是關於向列型液晶 7OCB ( 4-Cyano-4’-n-heptyloxybiphenyl )在電場作用之下其流變性質探討，其黏彈性質可藉由平板式流變儀( Physica MCR 301 )得到，其流變行為與電場強度及溫度有關，在其向列型液晶相溫度時，其剪應力會隨著電場強度增加而有所提升，並隨著溫度不同而有所變化。

關鍵字

液晶 ； 液晶高分子 ； 電流變效應

並列摘要

This study consist of two parts. The first part focuses on the electrorheological effect of homogeneous electrorheological fluid in regard to liquid crystalline
copolymer, PBLG-PDLG Poly(γ-benzyl L-glutamate-co-γ-dodecyl
L-glutamate),the molecule packing of α-helical poly(γ-benzyl L-glutamate) with n-alkyl side chain of various lengths (number of carbons in the alkyl group m = 12),
were studied by means of 1H-NMR and polarized optical microscope. The liquidcrystalline copolymer with the permanent dipole along the helix axis is expected to
show electrorheological effect under DC field. This study employed a parallel plate rheometer, Physica MCR 301, to investigate the viscosities of liquid crystalline
copolymer under the changes in electric field strength. An apparent increase in viscosity was found when the electric field was applied. It was attributed to the formation of molecule structures along the electric field resulted from the interaction between the liquid crystalline molecules. The flow resistance was consequently
enhanced. The second part is investigated the rheological properties of liquid crystal compound, 7OCB ( 4-cyano-4’-n-heptyloxybiphenyl ), subjected into an electric
field. The viscoelastic properties of the liquid crystals were measured by the parallel plate viscometer, Physica MCR 301. Similar to the previous study, the electrorheological behavior was depended on the electric field strengths and
temperatures. Within the temperature range of a nematic phase, the shear stress increase with amplitude of the electric field, and has different change with the
temperature.

並列關鍵字

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

參考文獻

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