ABSTRACT In order to investigate the photoalignment mechanism of nematic liquid crystals on an oxadiazoles, new 1,3,4-oxadiazole having fluorine atoms as terminal, as well as sideways was synthesized. Linearly polarized UV light shined in these nano-layered films causes the preferential direction of the liquid crystal molecules either perpendicular (in the case of terminal fluoro substitution) or parallel (in the case of sideways fluorine substitution) to the polarized direction. A powerful indication about the relationship between molecular structure and alignment properties where just by changing fluorine atom can change the entire alignment direction is proposed. Such information is indispensable for the design and synthesis of photoalignment materials for liquid crystal displays of high quality.
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R. Alaa, G. Hegde, A. Isloor, B. Chandrakantha, S. Malladi, M. Yusoff and L. Komitov, "Nano-engineering of New Photoreactive Materials Having Fluorine Units: Synthesis and Photoalignment of Liquid Crystals," Soft Nanoscience Letters, Vol. 3 No. 1, 2013, pp. 1-6. doi: 10.4236/snl.2013.31001.
 L. A. Masden,T. J. Dingemans, M. Nakata and E. T. Samulski, “Thermotropic Biaxial Nematic Liquid Crystals,” Physical Review Letters, Vol. 92, 2004, pp. 145505-145508. doi:10.1103/PhysRevLett.92.145505
 M. Grel, D. D. C. Bradley, M. Inbasekaran and E. P. Woo, “A Glass-Forming Conjugated Main-Chain Liquid Crystal Polymer for Polarized Electroluminescence Applications,” Advanced Materials, Vol. 9, No. 10, 1997, pp. 798-802. doi:10.1002/adma.19970091006
 C. Adachi, S. Tokito, T. Tsutsui and S. Saito, “Organic Electroluminescent Device with a Three-Layer Structure,” Japanese Journal of Applied Physics, Vol. 27, No. 4, 1988, pp. L713-L715. doi:10.1143/JJAP.27.L713
 J. Han, S. S.-Y. Chui and C.-M. Che, “Thermotropic Liquid Crystals Based on Extended 2,5-Disubstituted-1,3,4-oxadiazoles: Structure-Property Relationships, Variable-Temperature Powder X-Ray Diffraction, and Small-Angle X-Ray Scattering Studies,” Chemistry Asian Journal, Vol. 1, No. 6, 2006, pp. 814-825. doi:10.1002/asia.200600252
 S. Kobayashi and Y. Iimura, “Surface Liquid Crystal Molecular Alignment in LCDs and Their Electro-Optical Performance,” SPIE Proceedings, SPIE Photonics, Vol. 2175, 1994, p. 122.
 V. G. Chigrinov, M. Kozenkov and H. S. Kwok, “Photoalignment of Liquid Crystalline Materials: Physics and Applications,” Wiley Publication, Chichester, 2008.
 K. W. Lee, A. Lien, J. H. Stathis and S. H. Paek, “Control and Modification of Nematic Liquid Crystal Pretilt Angles on Polyimides,” Japanese Journal of Applied Physics, Vol. 36, 1997, pp. 3591-3597.
 O. Yaroshchuk and Y Reznikov, “Photoalignment of Liquid Crystals: Basics and Current Trends,” Journal of Materials Chemistry, Vol. 12, No. 2, 2012, pp. 286-300.
 O. Yaroshchuk, H. Gurumurthy, V. G. Chigrinov, H. S. Kwok, H. Hasebe and H. Takatsu, “Photoalignment Properties of Brilliant Yellow Dye,” International Display Workshop, Sapporo, 5-7 December 2007, p. 1665.
 M. Schadt, K. Schmitt, V. Koznikov and V. Chigrinov, “Surface-Induced Parallel Alignment of Liquid Crystals by Linearly Polymerized Photopolymers,” Japanese Journal of Applied Physics, Vol. 31, 1992, pp. 2155-2164.
 M. Schadt, H. Seiberle and A. Schuster, “Optical Patterning of Multi-Domain Liquid-Crystal Displays with wide Viewing Angles,” Nature, Vol. 381, No. 6579, 1996, pp. 212-215. doi:10.1038/381212a0
 L. O. Vretik, V. G. Syromyatnikov, V. V. Zagniy, E. A. Savchuk and O. Yaroshchuk, “Problem of Photoalignment in the LCD’s Development: Synthetic Routes in Its Solving,” Molecular Crystals and Liquid Crystals, Vol. 486, No. 1, 2008, pp. 57-65.
 S. Sato, H. Ito, T. Mizunuma, K. Nagai, H. Matsumoto and S. Matsumoto, “Substitute Effect of Fluorine-Containing Polyimides with Hexafluoroisopropylidine Group on Photoalignment of Liquid Crystal Molecule,” Journal of Photopolymer Science and Technology, Vol. 24, No. 6, 2011, pp. 617-623. doi:10.2494/photopolymer.24.617
 S. G. Hahm, S. W. Lee, T. J. Lee, S. A. Cho, B. Chae, Y. M. Jung, S. B. Kim and M. Ree, “UV-Driven Switching of Chain Orientation and Liquid Crystal Alignment in Nanoscale Thin Films of a Novel Polyimide Bearing Stilbene Moieties in the Backbone,” The Journal of Physical Chemistry B, Vol. 112, No. 16, 2008, pp. 4900-4912.
 B. Chandrakantha, P. Shetty, V. Nambiyar, N. Isloor and A. M. Isloor, “Synthesis, Characterization and Biological Activity of Some New 1,3,4-Oxadiazole bearing 2-Fluoro4-methoxy Phenyl Moiety,” European Journal of Medicinal Chemistry, Vol. 45, No. 3, 2010, pp. 1206-1210.
 H. Zhang, S. Shiino, A. Shishido and T. Ikeda, “A Thiophene Liquid Crystal as a Novel π-Conjugated Dye for Photo-Manipulation of Molecular Alignment,” Advanced Materials, Vol. 12, No. 18, 2000, pp. 1336-1339.