近年來液晶領域科學家利用具有旋性之液晶高分子製作出新穎之膽固醇液晶聚合物模板(簡稱模板)，此模板可有效改善純膽固醇液晶天生之光學侷限性，例如提高反射率超過50%、同時多波段反射、可彈性置換回填材料靈活改變其光學特性等。然而，過去的研究鮮少有系統性地定性針對液晶模板回填之物理機制與回填前後模板之光學行為做深入探討與研究。本論文有系統定性的研究發現回填入模板之向列型液晶，其黏滯係數與原樣品厚度會決定性地影響回填的模板樣品之螺距與光子能隙結構動態變化與最終飽和狀態。實驗可歸納出幾項重要結果:
(一) 液晶回填後，模板之光子能隙結構重現；隨著回填時間增加，光子能隙越趨完整化且漸漸紅移，紅移速度隨時間增加會漸緩最後終止。
(二) 使用具有不同黏滯係數之液晶分次回填入相同模板；黏滯係數越高者，回填後之模板光子能隙完整化與紅移速度越快，且最終紅移程度較大。
(三) 使用相同黏滯係數之液晶分次回填入厚度不同之模板樣品，模板厚度越薄者，回填後之光子能隙最終紅移之程度越大。
由實驗結果得知，形成的膽固醇液晶模板具有許多分布均勻之奈米孔洞(≦100 nm)，向列型液晶回填模板時會經由毛細現象滲入這些奈米孔洞，此滲入現象主要是由於回填之液晶本身同種分子間內聚力不足以抗衡液晶和模板孔洞壁之間異種分子間之附著力之結果，液晶回填會使得模板漸趨膨脹，模板螺旋結構漸趨完整，且螺距漸趨伸長，這就造成光子能隙結構漸趨完整且紅移。然而隨著回填比率越高，附著力會越小(乃由於可吸引液晶附著到孔洞壁的剩餘表面積越少)，這使得模板螺距伸長與光子能隙紅移隨時間增加而漸趨緩和。最終由於附著力降低至最低值與內聚力平衡，液晶回填動作終止，因此造成模板螺距伸長與光子能隙紅移亦終止。而黏滯係數越大之液晶注入同樣模板時，由於內聚力較大，使得滲入速率較慢，最後能滲入模板之飽和回填率亦較小，故模板螺距最終可伸展量較少，光子能隙最終可紅移量亦較少。另外，由模板之SEM側面與表面結構可知，對於同樣UV強度與照光時間下產生之模板厚度與奈米孔洞密度(單位體積)，樣品越厚者所製作出來模板雖越厚但奈米孔洞密度越小(模板聚合越紮實)，此會造成可回填之液晶最終回填率越少，螺距最終伸展量越少，模板之光子能隙最終紅移量越少。
最後，經由以上膽固醇液晶模板回填技術搭配楔形樣品可製作出一個具有相當厚度連續變化之楔形模板，此模板之高厚度梯度可導致空間上一個最終液晶回填率高梯度變化，而產生此楔形反射式光子元件之光子能隙具有可大範圍空間調控性，可空間調控程度達200 nm ( 495nm ~ 695nm)，幾乎接近全白光範圍。

The scientists in the field of liquid crystal (LC) exploited chiral LC polymer to fabricate novel cholesteric LC (CLC) polymer template (simply called template) in recent years. The template can effectively improve the limitation in the optical features of pure CLCs, such as enhancement of reflectivity over 50%, multiple reflection bands, and flexibly changeable optical characteristics by flexibly replacing the refilled LC materials. However, the past researches did not deeply investigate the underlying mechanism occurred in the refilling process of the template and the optical behaviors of the template before and after the refill systematically and qualitatively. The systematic and qualitative study in this thesis demonstrates that two factors, viscosity coefficient and cell thickness, crucially influence on the pitch of the spiral structure of the refilled template cell and thus the dynamic variation of its photonic bandgap (PBG) structure and final state in saturation. Several important experimental results can be summarized as follows:

(1) The PBG of the template restores after the refill of nematic LC (NLC). The PBG structure gradually completes and red-shifts with increasing the refilling time. The red-shift of the PBG becomes slowly with increasing time and ceases in final state.
(2) Four NLCs with various viscosity coefficients are individually refilled into the identical template. If the viscosity of the NLC is higher, both the rates for the completeness and red-shift of the PBG structure of the refilled template are faster and the total red-shift of the PBG is larger in final saturation state.
(3) The NLCs with identical viscosity are individually refilled into five template cells with various thicknesses. When the thickness of the template cell is thinner, the total red-shift of the PBG is larger in final saturation state.

Experimental results show that many nanopores (≦100 nm)can be formed uniformly in the CLC polymer template. When the NLC is injected into the template cell, the LC molecules may infiltrate into these nanopores due to the capillary phenomenon, as a result of that the adhesion between the hetero-molecules of the LC and the template of the nanopore walls is stronger than the cohesion between the LC molecules. The infiltration of the NLC may induce the gradual swell of the template and the gradual elongation of the pitch. This may cause the gradual completeness and red-shift of the PBG structure. When the refilling ratio in the nanopores of the template increases, the adhesion will decrease (due to the decreases of the residual surface areas on the wall of the nanopores to attract the LC molecules) such that the infiltration rate decreases and thus both the rates of the elongation of the pitch and the red-shift of the PBG decrease. In final state, the adhesion decreases to a minimum to balance with the cohesion such that the infiltration action stops and the refilling ratio saturates, and therefore both the pitch elongation and the PBG red-shift ceases. In addition, five CLC-monomer composite cells with various thicknesses are photopolymerized under the UV irradiation with same irradiated intensity and time. The experimental results of the obtained SEM template morphologies in side and top views indicate that the thickness of the template is thicker and the density of the nanopore (per unit volume) in the template is lower (that is, the polymerization to form the template is more compact and tighter) after the UV irradiation on a thicker CLC-monomer composite cell. This may result in a lower total refilling ratio of the NLC in the template, a lower total elongation of the pitch, and a lower total red-shift of the PBG of the template cell in final saturation state.
This thesis further fabricates a wide-band spatially tunable reflective photonic device using the above-mentioned refilling template technique in a CLC-monomer composite wedge cell. Through a uniform UV irradiation on the wedge cell, a wedgy template with a large gradient of thickness (2.44 ~ 19.92 m) can be formed, resulting in a large gradient of the total refilling ratio and thus a large band of spatial tunability in the refilled wedgy template photonic device. The total spatially-tunable reflective band for the wedgy template device is as wide as about 200 nm (495nm ~ 695nm), which covers almost the whole white light region.

1. P. G. de Gennes and J. Prost, The Physics of Liquid Crystals (Oxford University Press, New York, 1993).
2. White Timothy J, Natarajan Lalgudi V, Bricker, Rebecca L, Tondiglia Vincent P, Bailey Christopher, Bunning Timothy J, “Electromechanical and light tunable cholesteric liquid crystals” Opt. Commun. 18 (2010).
3. Shin-Ying Lu, Liang-Chy Chien, “A polymer-stabilized single-layer color
cholesteric liquid crystal display with anisotropic reflection” Appl. Phys. Lett. 91, 131119 (2007).
4. Ki-Han Kim, Dong Han Song, Zheng-Guo Shen, Byung Wok Park, Kyoung-Ho Park, Joun-Ho Lee, Tae-Hoon Yoon, “Fast switching of long-pitch cholesteric liquid crystal device” Opt. Express 19, No. 11 (2011).
5. D. C. O’shea, W. R. Callen and W. T. Rhodes, Introduction to Lasers and Their Applications (Addison Wesley, Boston, 1977).
6. V. I. Kopp, Z.-Q. Zhang, and A. Z. Genack, “Lasing in chiral photonic structures,” Prog. Quantum Electron. 27, 369–416 (2003).
7. 沈柯, 雷射原理教程 (亞東書局, 1990).
8. H. Kogelnik, and C. V. Shank, “Coupled-wave theory of distributed feedback lasers” J. APPl. Phys. 43, 2327-2335 (1972).
9. Hyunhee Choi, Junghee Kim, Suzushi Nishimura, Takehiro Toyooka, Fumito Araoka, Ken Ishikawa, Jeong Weon Wu, Hideo Takezoe “Broadband cavity-mode lasing from dye-doped nematic liquid crystals sandwiched by broadband cholesteric liquid crystal bragg reflectors” Adv. Mater. 22, 2680–2684 (2010).
10. Michel Mitov, Nathalie Dessaud, “Going beyond the reflectance limit of cholesteric liquid crystals” Nat. Mater. 5 (2006).
11. I. Dierking, L. L. Kosbar, A. Afzali-Ardakani, A. C. Lowe, G. A. Held, “Network morphology of polymer stabilized liquid crystals” Appl. Phys. Lett. 71, 2454 (1997).
12. Su Seok Choi, Stephen M. Morris, Wilhelm T. S. Huck, and Harry J. Coles, “Simultaneous red–green–blue reflection and wavelength tuning from an achiral liquid crystal and a polymer template” Adv. Mater 22, 53–56 (2010).
13. Jinbao Guo, Hui Cao, Jie Wei, Duowei Zhang, Fang Liu, Guohui Pan, Dongyu Zhao, Wanli He, Huai Yang “Polymer stabilized liquid crystal films reflecting both rightand left-circularly polarized light” Appl. Phys. Lett. 93, 201901 (2008).
14. Michael E. McConney, Vincent P. Tondiglia, Jennifer M. Hurtubise, Lalgudi V. Natarajan,Timothy J. White, Timothy J. Bunning, “Thermally induced, multicolored hyper-reflective cholesteric liquid crystals” Adv. Mater. 23, 1453–1457 (2011).
15. Michael E. McConney, Vincent P. Tondiglia, Jennifer M. Hurtubise, Timothy J. White, Timothy J. Bunning, “Photoinduced hyper-reflective cholesteric liquid crystals enabled via surface initiated photopolymerization” Chem.Commun. 47, 505–507 (2011).
16. F. Castles, F. V. Day, S. M. Morris, D-H. Ko, D. J. Gardiner, M. M. Qasim, S. Nosheen, P. J.W. Hands, S. S. Choi, R. H. Friend, H. J. Coles, “Blue-phase templated fabrication of three dimensional nanostructures for photonic applications” Nat. Mater. 11 (2012).
17. S. Chandrasekhar, Liquid Crystals (Cambridge University Press, New York, 1992).
18. Letter form F. Reintzer to O. Lehmann, reported by H. Kelker, Mol. Cryst. Liq. Cryst. 21,1 (1973).
19. I. C. Khoo, Liquid Crystals: Physical Properties and Nonlinear Optical Phenomena (John wiley and Sons, New York, 1995).
20. G. Chilaya, “ Cholesteric liquid crystal: “Optics, electro-optics, and photo-optics”, in Chirality in Liquid Crystals, Eds. H. S.Kitzerow and Ch. Bahr, Springer, New York (2001).
21. P. G. de Gennes, Sol. State Commun. 6, 163 (1968).
22. R. B. Meyer, Appl. Phys. Lett. 12, 281 (1968).
23. L. M. Blinov and V. G. Chigrinov, “Electro-optic Effects in Liquid Crystal Materials,” Springer-Verlag, New York (1994).
24. 李佳榮, ”液晶-聚合物混合薄膜全像光柵中光偶和動態效應之研究”, 國立成功大學物理研究所碩士論文 (1999)。
25. 陳哲昶, “偶氮染料摻雜液晶-高分子球型聚合物薄膜垂直吸附效應之研究及其應用” 國立成功大學光電科學與工程研究所碩士論文 (2008) 。
26. Jinbao Guo, Jie Sun, Kexuan Li, Hui Cao, Huai Yang, “Reflectance properties of polymer-stabilised cholesteric liquid crystals cells with cholesteryl compounds of different functionality” Liquid Crystals, 35 (2008).
27. Harry. J Coles, Mikhail N. Pivnenko, “Liquid crystal blue phases with a wide temperature range” Nature Letters, 436 (2005).
28. Michel MIitov, Nathlie Dessaud, “Going beyond the reflectance limit of cholesteric liquid crystals” Nat. Mater. , 5 (2006).
29. Jui-Hsiang Liu, Hao Fang, Chih-Chieh Chien, “Solvent-Tunable colors in imprinted helical structures on polymer template via multiple UV-induced polymerization” Polymer Science, 49, 1256-1262 (2011).
30. 方皓 “膽固醇型液晶拓印之光子晶體結構及其光學特性之探討” 國立成功大學化學工程研究所碩士論文 (2011) 。
31. Shin-Tson Wu and Deng-Ke Yang “Reflective Liquid Crystal Displays”, John Wiley & Sons, New York (2001)
32. H. Yamada, I. Manas-Zloczower, D. L. Feke, “Observation and analysis of the infiltration of polymer liquids into carbon black agglomerates” Chemical Engineering Science 53 (1997).
33. F. Bohin, D.L. Feke, I. Manas-Zloczower, “Determination of the infiltration kinetics of polymer into filler agglomerates using transient buoyancy measurements” Powder Technology 83 (1995).
34. Heertjes, P. M. and Kossen, “Measuring the contact angles of powderÐliquid system” Powder Technology 33 (1967).
35. Wu. S, and Brzozowski, “Surface free energy and polarity of organic pigments” J. Colloid Interface Sci. 37 (1971).
36. Wu. S, “Polymer Interface and Adhesion” Marcel Dekker, New York. (1982).
37. Mi-Yun Jeong, Hyunhee Choi, J. W. Wu, “Spatial tuning of laser emission in a dye-doped cholesteric liquid crystal wedge cell” Appl. Phys. Lett. 92, 051108 (2008).