光是種環保的能源，具遠程控制性等優點，偶氮苯類衍生物是目前被廣泛研究的光響應材料，在一般穩定情況下處於反式(trans-)狀態呈棒狀結構，藉由照射激發光後，部分偶氮苯分子能夠藉由光激發同素異構化反應形成彎曲結構的順式(cis-)狀態，使材料產生性質上或體積上的改變。目前已有研究將偶氮苯應用在液晶高分子薄膜上，利用其光響應特性使薄膜產生光致形變的效果如彎曲、伸縮或是更複雜的運動現象，並將此特性進行多種應用如光控刷毛、馬達等。
　　本研究利用具偶氮苯基團液晶摻入高分子材料與旋性物質製作一光致形變膽固醇液晶薄膜，藉由偶氮苯分子之光激發同素異構化的反應，使薄膜表面產生體積上的伸縮，進一步使高分子網絡產生宏觀的形變。由於偶氮苯分子對於不同偏振方向激發光的吸收具異向性，因此利用不同偏振方向的激發光便能控制週期性螺旋排列的膽固醇液晶薄膜的彎曲方向。此外由於週期性的折射率分布，膽固醇液晶在planar texture時可被視為一選擇波段反射之布拉格反射膜，因此利用此光致形變的效應，膽固醇液晶膜可以藉由光場控制其反射角度也可以控制其彎曲角度來選擇反射/過濾的波段而製作成一布拉格反射鏡或是濾波器。光控膽固醇液晶薄膜反射鏡/濾波器相較傳統電控可免去接電路的不便且可進行區域化調控。
本研究藉由不同的液晶配向方法與不同激發光的偏振方向來探討與光致形變液晶薄膜照光後彎曲方向之關係，觀察照光強度對薄膜彎曲速度的影響以及薄膜光致形變的重複性，最後對光致形變膽固醇液晶薄膜的特性與應用進行討論及比較。

Light is a rich and clean source of energy. Azobenzene derivatives are widely studied regarding their responses to light. Most of azobenzenes are intrinsically stable in its trans form, a rod-like structure. Upon actinic irradiation, the trans-azobenzenes experience an isothermal transition from trans- to cis-state. This process is called photo-isomerization and normally causes changes in the azobenzenes’ physical properties, such as volume. Recently, azobenzenes and their photo-isomerization effects are applied to produce light-responsive liquid-crystal polymer actuators. By exploiting light-induced deformation of these azobenzene polymers (e.g. bending, contraction or rotation), optomechanical motors, oscillators and artificial muscles were demonstrated.
In this work, we photo-polymerized mixtures that consist of an azobenzene liquid crystal monomer, a crosslinker and a chiral dopant to produce photo-responsive cholesteric-liquid-crystal polymer films. Due to the absorption anisotropy of the azobenzene liquid crystal and the helical director distribution of the planar cholesteric texture, the cholesteric liquid crystal film can be bent in arbitrary direction that is determined by polarization direction of the incident linearly polarized light. In conjunction with the Bragg reflection characteristic of the cholesteric liquid crystal, the polymer film can act as an optically controllable dielectric mirror and color filter; the reflection angle and the filtered spectrum can be controlled by light. With respect to traditional electrically controlled actuator, photo-responsive polymers features tether-free control, addressability and self-modulation.
In this thesis, we investigated the relationship among polarization, alignment and bending directions in photo-responsive polymer films with various director axis distribution. The rate and repeatability of bending were also discussed. In the last part, we demonstrated possible applications of the photo-responsive cholesteric liquid crystal polymer films.

論文審定書 i
摘要 ii
Abstract iii
目錄 v
圖錄 viii
表錄 xi
緒論 1
第一章 液晶介紹 2
1-1 何謂液晶 2
1-2 液晶的分類 3
1-2.1 向列型液晶 4
1-2.2 層列型液晶 4
1-2.3 膽固醇型液晶 5
1-3 液晶的物理性質 6
1-3.1 秩序參數[6] 6
1-3.2 光學異向性(雙折射性)[7] 6
1-3.3 介電常數異向性 9
1-3.4 連續彈性體理論[8, 9] 10
1-3.5 黏滯係數異向性[6] 11
1-4 膽固醇液晶簡介 12
1-4.1 膽固醇液晶結構介紹 12
1-4.2 膽固醇液晶的平面螺旋結構與光學性質 13
1-4.3 膽固醇液晶的排列結構 14
第二章 液晶彈性薄膜介紹 17
2-1 液晶彈性薄膜簡介 17
2-2 液晶彈性薄膜的形變效應 18
2-3 光致形變液晶薄膜簡介 20
2-4 光致形變液晶薄膜的彎曲現象 22
2-5 光致形變液晶薄膜的應用 24
第三章 實驗方法與過程 26
3-1 材料介紹 26
3-2 光致形變液晶薄膜製備 28
3-2.1 光致形變膽固醇液晶薄膜製備流程 28
3-2.2 液晶盒配向製備 30
3-3 實驗架設與量測 33
3-3.1 液晶相變與配向的觀察 33
3-3.2 穿透頻譜量測 34
3-3.3 反射頻譜量測 35
3-3.4 光致形變液晶薄膜彎曲方向觀察 36
3-3.5 光致形變液晶薄膜彎曲特性量測 37
第四章 實驗結果與討論 38
4-1 光致形變液晶薄膜彎曲方向與表面配向關係 38
4-1.1 水平配向 38
4.1.2 垂直配向 39
4-1.3 TN配向 40
4-1.4 圓配向 41
4-2 光致形變膽固醇液晶薄膜彎曲方向與激發光偏振關係 44
4-3 光致形變膽固醇液晶薄膜彎曲速度與激發光強度關係 46
4-4 光致形變膽固醇液晶薄膜應用 49
4-4.1 布拉格反射鏡 49
4-4.2濾波器 53
第五章 結論與未來展望 55
參考文獻 57

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