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Design and synthesis of ferroelectric liquid crystals. 24. Incorporation of the disperse red 1 chromophqre into side-by-side dimers for nonlinear optics

  • Daniel J. Dyer (a1), Renfan Shao (a2), Noel A. Clark (a2) and David M. Walba (a1)

Abstract

With excellent processibility on silicon integrated circuits and thermodynamically stable polar order, ferroelectric liquid crystals (FLCs) show great potential as components of fast integrated electro-optic modulators. In order to realize this potential, however, an increase in the magnitude of the electronic secona order nonlinear susceptibility χ(2) is required. This has been problematical since functional arrays with large molecular second order susceptibility β orient with improper supermolecular stereocontrol (i.e. with the charge transfer axis normal to the polar axis) when incorporated into traditional FLC structures. Herein we present examples of a new LC structural class designed to achieve the proper supermolecular structure for large χ(2) in FLCs. The observed sign and magnitude of the ferroelectric polarization of the new mesogens extrapolated from smectic C* mixtures is fully consistent with the desired supermolecular structure.

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1 For previous papers in the series see: (a) Walba, D. M.; Dyer, D. J.; Cobben, P. L.; Sierra, T.; Rego, J. A.; Liberko, C. A.; Shao, R.; Clark, N. A. Ferroelectric Liquid Crystals for Nonlinear Optics Applications: Can we Really Do It?; in Thin Films for Integrated Optics Applications, Wessels, B. W., Marder, S. R. and Walba, D. M., Eds.; Materials Research Society: Pittsburgh, PA, 1995; Vol.392, pp 157162, and references therein. (b) Walba, D.M.; Dyer, D.J.; Sierra, T.; Cobben. P.L.; Shao, R.; Clark, N.A. J. Am. Chem. Soc. 1996, In Press.
2 Arnett, K. E.; Walba, D. M.; Drewes, J. A. Technique for Measuring Electonic-Based Electro-Optic Coefficients for Ferroelectric Liquid Crystals; in Thin Films for Integrated Optics Applications, Wessels, B. W., Marder, S. R. and Walba, D. M., Eds.; Materials Research Society: Pittsburgh, PA, 1995; Vol.392, pp 135146.
3 (a) Walba, D.M.; Ros, M.B.; Sierra, T.; Rego, J.A.; Clark, N.A.; Shao, R.; Wand, D.M.; Vohra, R.T.; Arnett, K.E.; Velsco, S.P. Ferroelectrics 1991, 121, 247. (b) Schmitt, K.; Herr, R.P.; Schadt, M. FUnschilling, J.; Buchecker, R.; Chen, X.H.; Benecke, C. Liq. Crrst. 1993, 14, 1735.
4 Walba, D.M. Science 1995, 270, 250.
5 (a) Williams, D.J. Angew. Chem., Int. Ed. Engd. 1984, 23,690. (b) Quantum Chemical Computational Calculation of Nonlinear Susceptibilities of Organic Materials; Bredas, J.L.; Garito, A.F.; Ito, Y., Eds.; Special Issue of Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. B; Gordon & Breach: Basel, Switzerland, 1994; Vol.6 (3–4), pp 135. (c) Kanis, D.R.; Ratner, M.A.; Marks, T.J. Chem. Rev. 1994, 94, 195. (d) Meyers, F.; Marder, S.R.; Pierce, B.M.; Bredas, J.L. J. Am. Chem. Soc. 1994, 116, 10703.
6 Kobayashi, S.; Ishibashi, S.; Tsuru, S. Mol. Cryst. Liq. Cryst. Letters 1990, 7, 105.
7 Interesting examples include: (a) Fouquey, C.; Lehn, J.M.; Malthete, J. J. Chem. Soc. Chem. Commun. 1987, 1424. (b) Berdague, P.; Bayle, J.P.; Ho, M.S.; Fung, B.M. Liq. Crvst. 1993, 14, 667. (c) Ikeda, T.; Sasaki, T.; Ichimura, K. Nature 1993, 361, 428. (d) Sasaki, T.; Ikeda, T.; Ichimura, K. J. Am. Chem. Soc. 1994, 116., 625.
8 Some examples of LC dopants with negative dichroism, wherein dye units orient at a large angle relative to the LC director upon dissolution in an LC host, have been reported: (a) Ivashchenko, A.V.; Petrova, O.S.; Titiov, V.V. Mol. Cryst. Liq. Cryst. 1984, 108, 51. (b) Rumyantsev, V.G.; Ivashchenko, A.V.; Muratov, V.M.; Lazarreva, V.T.; Prudnikova, E.K.; Blinov, L.M. Mol. Cryst. Liq. Cryst. 1983, 94, 205. See also reference 1.
9 Walba, D.M. Ferroelectric Liquid Crystals: A Unique State of Matter; in: Advances in the Synthesis and Reactivity of Solids; Mallouk, T.E., Ed.; JAI Press Ltd: Greenwich, Connecticut, 1991; Vol.1, pp 173235.
10 Glaser, M. A.; Ginzburg, V. V.; Clark, N. A.; Garcia, E.; Walba, D. M.; Malzbender, R. Molecular Physics Reports 1995, 10, 2647.
11 The properties of this material have been reported in detail: (a) Walba, D.M.; Ros, M.B.; Clark, N.A.; Shao, R.; Johnson, K.M.; Robinson, M.G.; Liu, J.Y.; Doroski, D., in Materials for Nonlinear Optics: Chemical Perspectives, Stucky, G.D., Ed.; Americal Chemical Society, Washington DC, 1991; pp 484. (b) Walba, D.M.; Ros, M.B.; Clark, N.A.; Shao, R.; Robinson, M.G.; Liu, J.Y.; Johnson, K.M.; Doroski, D. J. Am. Chem. Soc. 1991, 113, 5471.
12 A PNA derivative developed at Roche (see reference 3b) exhibited a pe ≈. 10% when the dimethylamino group was situated ortho to the alkyloxy tail, while the flipped configuration yielded pe ≈ 30% (see reference la).
13 All new compounds reported herein showed consistent 1H and 13C NMR spectra, mass spectra, and gave satisfactory combustion analysis. The synthesis of these compounds will be reported elsewhere.
14 A dipole moment of 5.7 Debye perpindicular to the director was calculated for compound 1 using MOPAC and AM I parameters. The observed P yields a ferroelectric dipole density of 0.5 D/molecule along fi, suggesting a 9% polar excess. A dipole moment of 9.2 Debye perpindicular to the director was calculated for compound 2. The observed P yields a dipole density of 2.0 D/molecule along , suggesting a 22% polar excess.

Design and synthesis of ferroelectric liquid crystals. 24. Incorporation of the disperse red 1 chromophqre into side-by-side dimers for nonlinear optics

  • Daniel J. Dyer (a1), Renfan Shao (a2), Noel A. Clark (a2) and David M. Walba (a1)

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