聚合物穩定膽固醇液晶結構 (Polymer-stabilized Cholesteric Texture，簡稱PSCT)，以聚合物枝條穩定膽固醇液晶之排列，通過外加電場、光源 (light source) 實現樣品的穿透和散射。
在本研究中，以偶氮苯液晶聚合物 (Azobenzene Liquid crystalline polymer) 取代傳統聚合物材料穩定膽固醇液晶結構，實現在膽固醇液晶的焦錐結構 (focal conic texture)、各向同性態 (isotropic state) 及平面結構 (planar texture) 間的全光控切換。這三種結構可以利用在兩種切換模式上，分別為膽固醇焦錐結構和各向同性態間之可逆切換，及膽固醇焦錐結構和平面結構間之可逆切換，切換對比度皆可以達80:1。
光切換的原理是利用偶氮苯分子經由光照後由長棒狀的trans-態轉變為彎曲狀的cis-態并擾亂液晶排列使其秩序參數下降，從而使其相變溫度降低，當液晶混合物中cis-態濃度超過一臨界值時，液晶就會發生等溫相變。同時我們也驗證了偶氮苯液晶聚合物處於cis-態時在液晶中的溶解度會有明顯提高。因此分別利用聚合物在trans-態時的網狀結構、等溫相變的特性以及在偶氮苯液晶聚合物cis-態結構在液晶中之高溶解度，形成膽固醇液晶的焦錐結構、平面結構及各向同性態，達成全光控及快速反應。

Azobenzene can be made to transit between trans- and cis- state photochemically. The chemical structures of the former and the latter are rode- and bend- shape, respectively. Being doped in a liquid crystal (LC) cell, the trans-cis isomerization can, thus, decrease the LC order due to bend structure of the cis-isomers, and lower the nematic-to-isotropic phase transition temperature. Notably, once the cis-isomers reach a critical concentration, a nematic LC can be isothermally transited to the isotropic state. We also verify that the cis-isomer of azobenzene liquid crystalline polymer performs a high solubility in the LCs. These features motivated us to use the azobenzene liquid crystalline polymer instead of a traditional polymer to achieve all-optically controllable switching among the focal conic texture, planar texture and isotropic state in a cholesteric LC cell. These three stable textures can be used to achieve two switching modes between the transparent and scattering states. One is the reversible switching between isotropic state and focal conic texture, and the other is the reversible switching between the planar texture and focal conic texture. Both modes display high contrast ratio (80:1). Moreover, the switching is fast, with a timescale ranging from milliseconds to seconds.

[1] Gregory Philip Crawford and Slobodan Žumer, "Liquid Crystals in Complex Geometries-Formed by polymer and porous networks" (CRC Press, 1996).
[2] H. Finkelmann, E. Nishikawa, G. G. Pereira and M. Warner, Phys. Rev. Lett. 87, 015501 (2001).
[3] M.-H. Li, P. Keller, B. Li, X. Wang and M. Brunet, Adv. Mater. 15, 569-572 (2003).
[4] M. Warner and E. Terentjev, Macromol. Symp. 200, 81-92 (2003).
[5] Y. L. Yu, M. Nakano and T. Ikeda, Nature 425, 145 (2003).
[6] M. Camacho-Lopez, H. Finkelmann, P. Palffy-Muhoray and M. Shelley, Nat. Mater. 3, 307-310 (2004).
[7] C. Ohm, M. Brehmer and R. Zentel, Adv. Mater. 22, 3366-3387 (2010).
[8] Paul S. Drzaic, J. Appl. Phys. 60, 2142 (1986).
[9] A. Y. -G. Fuh, C. -Y. Huang, B. -W. Tzen, Jpn. J. Appl. Phys., part l 33, 1088 (1994).
[10] Tong X, Wang G, Yavrian A, Galstian T, Zhao Y., Adv Mater 17, 370-374 (2005b).
[11] H. Kikuchi,Yokota M., Y. Hisakado, H. Yang and T. Kajiyama, Nature Materials 1, 64 (2002).
[12] 謝毓章，《液晶物理學》，第一版，科學出版社，1988。
[13] Pochi Yeh, and Claire Gu, "Optics of Liquid Crystal Displays" (Wiley, 1999).
[14] S. Chandrasekhar, "Liquid Crystals", 2th ed. (Cambridge University Press, 1992).
[15] P. G. de Gebbes and J. Prost, "The Physics of Liquid Crystals", 2th ed. (Oxford University Press, 1993).
[16] Heinz-Siegfried Kitzerow, Christian Bahr, and Christian Bahr, "Chirality in Liquid Crystals" (Springer, 2001).
[17] A. Yariv, "Optical Electronics in Modern Communications" (Oxford University Press, 1997).
[18] A. Yariv, "Quantum Electroics" (Wiley, 1988).
[19] S. Chandrasekhar, B. K. Sadashiva, and K. A. Suresh, Pramana 9, 471-480 (1977).
[20] W. Helfrich, C. S. Ho, Mol. Cryst. Liq. Cryst. 14, 289 (1971)
[21] Deng-Ke Yang and Shin-Tson Wu, "Fundamentals of Liquid Crystal Devices” (Wiley, 2006).
[22] M. Marinelli and F. Mercuri, Phys. Rev. E 61, 1616-1621 (2000).
[23] Peter J. Collings and Michael Hird, "Introduction to Liquid Crystals Chemistry and Physics" (2001)
[24] R. Hochgesand, H. J. Plach, and I. C. Sage, technical report by E. Merck and BDH Chemicals Ltd. (1989).
[25] C. W. Oseen, Trant. Faraday Soc. 29, 883 (1933).
[26] F. C. Frank, Disc. Faraday Soc. 25, 19 (1958).
[27] Jun Geng, Chen Dong, Lipei Zhang, Zheng Ma, Lin Shi, Appl. Phys. Lett. 89, 081130 (2006).
[28] W. M. Gibbons, P. J. Shannon, S. T. Sun and B. J. Swetlin, Nature 351, 49 (1991).
[29] H. K. Lee, A. Kanazawa, T. Shiono and T. Ikeda, Chem. Mater. 10, 5 (1998).
[30] Mita I, Horie K, Hirao K, Photochemistry in polymer solids. 9. Macromolecules 22, 558-563 (1989).
[31] Yue Zhao, Tomiki Ikeda, "Smart Light-Responsive Materials: Azobenzene-Containing Polymers and Liquid Crystals" (Wiley, 2009).
[32] Lednev IK, Ye T-Q, Hester RE, Moore JN, J Phys Chem 100, 13338-13341 (1996).
[33] Rottger D, Rau H, J Photochem Photobiol A Chem 101, 205-214 (1996).
[34] A. G. Chen and D. J. Brady, Opt. Lett. 17, 441 (1992).
[35] T. V. Gastyan, V. Drnoyan and S.M. Arakelian, Phys. Lett. A 217, 52 (1996).
[36] Kato T, Hirota N, Fujishima A, Frechet JMJ, J Polym Sci, Part A 34, 7-62 (1996).
[37] Hayashi T, Eur Polym J 31, 23-28 (1995).
[38] Ikeda T, Tsutsumi O, Science 268, 1873-1875 (1995).
[39] Berreman D W, Phys. Rev. Lett. 28, 1683 (1972).
[40] Paul S. Drzaic, "Liquid crystal dispersions" (World Scientific Singapore, 1995).
[41] M. Kerker, "The Scattering of Light and Other Electromagnetic Radiation" (Academic Press, 1969).
[42] H. C. Van de Hulst, "Light Scattering by Small Particles" (Dover Publications, 1957).
[43] CB 15, http://www.thsci.com/97730-31-9.html
[44] Svetlana Serak, Nelson Tabiryan, Rafael Vergara, Timothy J. White, Richard A. Vaia and Timothy J. Bunning, Soft Matter 6, 779-783 (2010).