A soluble, asymmetric polydiacetylene has been shown to form stable monolayers at the air−water interface of a Langmuir trough. The monolayers of this unconventional amphiphilic polymer could be repeatedly deposited onto hydrophobic substrates during every upstroke cycle of the vertical dipping method to form uniform Z-type multilayers. Characterization of the precise orientation of the polymer main chain has been carried out to determine the spatial correlation between the nonlinear optical chromophore responsible for second-order nonlinear optical properties and the backbone. Polarized UV/vis and IR spectroscopic studies indicate a preferential orientation of the main chain along the dipping direction with a mean fluctuation of ±30° between director axis and chain trajectories. Polarization-dependent second-harmonic generation (SHG) in multilayers indicates a high degree of orientational anisotropy of the backbone. As expected, SHG intensities increase with the number of layers due to the noncentrosymmetric Z-type structure. The second-order nonlinear coefficient (d 33) was estimated to be 1.52 pm/V at 1064 nm of Nd:YAG laser after correcting for absorption. Surface characterization and alignment of the extended chain backbones is further established using atomic force microscopy (AFM).

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A soluble, asymmetrically substituted polydiacetylene, poly(BPOD), has been reported to form stable monolayers at the air-water interface by the Langmuir-Blodgett (LB) technique [2]. Preformed polydiacetylene has been deposited onto hydrophobic substrates as multilayers to form second order nonlinear optical thin films. Second harmonic generation was found to increase with the number of layers. From previous atomic force microscopy (AFM) studies backbone orientation along the dipping direction with an interchain spacing of about 5 A° was indicated [2].The film morphology and preferential molecular orientation of these LB films are further investigated by transmission electron microscopy (TEM). A specifically tailored sample preparation method for the ultrathin LB films was used. Multilayer films were deposited on hydrophobic collodion covered glass substrates for this purpose. Electron diffraction was employed to study the crystalline organization of mono and multilayers of LB films as well as cast films.

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Reproduction in whole or in part is permitted for any purpose of the United States Government. This document has been approved for public release and sale; its distribution is unlimited. ABT I RAG T (MaxImum ZOO WOW~s)Second harmonic generation from the spin coated films of an asymmetrically substituted polydiacetylene, namely poly((8-butoxy cardonyl)methyl urethanyl) 1-(5-pyrimidyl)-octa-1,3-diyne(BPOD) is reported for the first time. The macromolecules assemble to produce the organization responsible for SHG without recourse to poling. d33 of the spin coated film (0.19-0.31 mm thickness) are between 0.78-0.88 pm/V without absorption correction and 3.32-5.57 pm/V after correction. Angular and polarization dependence study of the second harmonic response suggests that the film has in-plane isotropy as a whole and the net dipole is nearly perpendicular to the film surface. Spontaneous orientation of the polymer chains during the film formation seems to be responsible for the noncentrosymmetric alignment of the polymer. SHG from the Langmuir Blodgett films are also reported. ABSTRACT Second harmonic generation from the spin coated films of an asymmetrically substituted polydiacetylene, namely poly((8-butoxy carbonyl)methyl urethanyl) 1-(5-pyrimidyl)-octa-l,3-diyne(B POD) is reported for the first time. The macromolecules assemble to produce the organization responsible for SHG without recourse to poling. d 33 of the spin coated film (0.19-0.31 gmn thickness) are between 0.78-0.88 pm/V without absorption correction and 3.32-5.57 pm/V after correction. Angular and polarization dependence study of the second harmonic response suggests that the film has in-plane isotropy as a whole and the net dipole is nearly perpendicular to the film surface. Spontaneous orientation of the polymer chains during the film formation seems to be responsible for the noncentrosymmetric alignment of the polymer. SHG from the Langmuir Blodgett films are also reported.