Orientation of Main-Chain Accordion Polymers Having Different Alkyl Chains. SEUNG-HWAN LEE, TOSHIYUKI WATANABE, KAORU KAGOSHIMA, SHIRO FUJITA, SHINRO MASHIKO, MOSTAFA TALUKDER, GEOFFREY A. LINDSAY, W N.HERMAN, KENNETH J. WYNNE and SEIZO MIYATA Abstract The molecular orientations of home Y-type LB films of main-chain accordion having different alkyl chain (R = l2 and l6) are investigated. The home Y-type LB films were prepared by using Miyata-type deposition system. The nonlinear optical coefficients of d33 for R = l2 and R = l6. from the result of reflected SHG intensity, are 12.0 and 8.6 pm/V. respectively. The bilayer spacing a home Y-type LB films value from the result of wide angle X-ray diffraction (WAXD) spectra is shorter than the fully extended length of each molecule by CPK model. From the Maker-fringe for Y-type LB films, the SHG strength become the strongest when the P-P polarization was greatly slanted in the substrate. These results reveal that spontaneous polarization remains along the thickness direction. We proposed the structure of a new home Y-type LB film which is different arrangement between odd-numbered layer and even-numbered layer.