The Effect of Exposure Energy on the Photoalignment of Liquid Crystals Using Coumarin-Containing Copolymer Film

doi:10.7517/j.issn.1674-0475.2013.06.456

Abstract

Abstract:

In this article, two monomers were synthesized. One is with photosensitive group and another contains nothing but a mesogenic unit. Copolymer was obtained by free radical polymerization. When the copolymer film is exposed to the linearly polarized ultraviolet light (LPUV), it can generate a polarization-axis selective photoreaction. The photoalignment performance of the synthesized copolymer was tested preliminarily using dynamic UV spectrum. The results indicate that when the exposure energy gets to 1740 mJ/cm², the UV absorption do not change with the increasing of exposure energy. At the early stage, the rate of photoreaction is very fast. When the exposure energy is 500 mJ/cm², the degree of photoreaction is more than 50%. A large anisotropy ΔA_max=0.039 was generated when the exposure energy gets to 324 mJ/cm².

Key words: liquid crystal, photosensitive group, coumarin, anisotropy, photoalignment

CLC Number:

CAO Jin, ZHANG Wei-min, YANG Jiao, PU Jia-ling. The Effect of Exposure Energy on the Photoalignment of Liquid Crystals Using Coumarin-Containing Copolymer Film[J]. Imaging Science and Photochemistry, 2013, 31(6): 456-462.

References

[1] 周期凤,王新久.液晶高分子[M].北京:科学出版社,1994, 1-116. Zhou Q F, Wang X J. Polymer Liquid Crystal [M]. Beijing: Science Press, 1994, 1-116.

[2] Kunihiro Ichimura. Photoalignment of liquid-crystal systems[J]. Chemical Reviews, 2000, 100(5):1847-1874.

[3] Gibbons W M, Shannon P J, Sun S T, et al. Swetlin, surface-mediated alignment of nematic liquid crystals with polarized laser light[J]. Nature, 1991, 351: 49-50.

[4] Hyo Kang, Daeseung Kang, Jong-Chan Lee. Liquid crystal alignment properties of polystyrene derivatives containing coumarin side groups[J]. Liquid Crystals, 2008, 35(8):1005-1013.

[5] 纪小妹,焦阳,魏杰.液晶光定向材料研究进展[J].信息记录材料,2008, 9(4): 33-41. Ji X M, Jiao Y, Wei J. Development of research on LC light control materials[J]. Information Recording Materials, 2008, 9(4): 33-41.

[6] Peter S, Isabel M S. Side chain liquid crystal polyacrylate and polymethacrylate nickel complexesfree from covalent cross-linking[J]. Molecular crystals and liquid crystals, 2004, 411(1): 491-502.

[7] Jackson P O, O'Neill M. An investigation of the role of cross-linking and photodegradation of side-chain coumarin polymers in the photoalignment of liquid crystals[J]. Chemistry of Materials, 2001, 13(2):694-703.

[8] 冯利邦,方红霞,周树学,顾广新,武利民. 一步法制备聚二甲基硅氧烷大分子偶氮引发剂及其用于嵌段共聚物的合成[J].高分子学报,2007, (5): 472-477. Feng L B, Fang H X, Zhou S X, Gu G X, Wu L M. Synthesis of PDMS-containing macroazoinitiator by one step method and its application in preparation of block copolymers[J]. Acta Polymerica Sinica, 2007, (5): 472-477.

[9] Michael P, Ringsdorf H, Zentel R. Synthesis and phase behaviour of liquid crystalline polyacrylates[J]. Die Makromolekulare Chemie, 1982, 183(10): 2311-2321.

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