Photo-Induced Properties of Liquid Crystal Molecules on Alternately Assembled Charged Azobenzene Dyes and Polyelectrolyt
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ammonium chloride) (PDADMAC) self-assembled films [9] on the gold electrodes using the ATR measurement method. From the ATR curves, in-plane switching properties of the LC molecules and the orientation in the LC cell were evaluated during and after the irradiation of linearly polarized light. The molecular assembly processes of individual polyion-dye pairs for fabrication of new photo-aligning layers were also investigated using ATR measurements. EXPERIMENT Figure 1 shows the Kretschmann configuration for the ATR measurements, the LC cell and the molecular structures of the polyion (PDADMAC) and the azo dye (DR80) used in the experiments. p-pol. detector Figure 1. The Kretschmann configuration for the ATR Y measurements, the LC cell and the X molecular structures. Z half-cylindrical
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The half-cylindrical prisms (HOYA FDS90, n=1.85) were used Au for the ATR measurements. Gold L.C. (5CB) films approximately 40 nm thick were PDADMAC/DR80 slide glass vacuum evaporated onto the flat side of the prisms. Afterwards, the surface Polarized Light of the prisms with gold films was functionalized with 3-aminopropyl triethoxysilane and the layer-by-layer adsorption of the DR80/PDADMAC self-assembled films were done. The Cl N H C CH procedure is as follows: the molecular layers of the PDADMAC and the PDADMAC (Polycation) DR80 were alternately deposited from these aqueous solutions with 0.01 M on the coated prisms and slide glasses as the aligning layers of the LC cell. These self-assembled films had 5 DR80 bilayers on the coated prisms and 100 (Anion) bilayers on the slide glasses. Each deposition on these substrates was carried out for 15 minutes including the immersion and a rinsing step in deionized water. The alignment layers of the DR80/PDADMAC films on the prism were irradiated with linearly polarized visible light in the x-direction before fabricating the LC cell. A high dichroism (by UV-vis spectroscopy) of the DR80/PDADMAC films due to the n-π* transition of azobenzene dyes (DR80) by the irradiation has been observed in our previous report [10]. Reflectivities of the ATR experiments were measured for the LC cell as a function of the incident angles of a He-Ne laser at 632.8 nm, or at the resonant incident angle of the SPP during the irradiation of the linearly polarized visible light to the cell through the slide glass without irradiation (as shown in Fig. 1). The nematic liquid crystal was 4-cyano-4'-n-pentylbiphenyl (5CB: Merck Japan Co.). prism
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Furthermore, the complex dielectric constants and the thicknesses of the gold films on the prisms and the DR80/PDADMAC films were determined from the ATR measurements using another type of prism (BK 7, n = 1.515) before the ATR measurements of the LC cells. 1
Figure 2. Calculated ATR curves of the LC cell
homeotropic state
nÛ Reflectivity
Figure 2 shows the calculated ATR curves for the four idealized cases n due to the excitation of the SPP, assuming that planer the tilt angles of the (nÛ ) nema
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