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Abstract:
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 up-stroke 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 + or - 30 deg 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 sub 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).
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Technical rept. |
| Pages: |
32 |
| Report Date: |
31 OCT 95 |
| Contract Number: |
N00014-90-J-1148 |
| Report Number: |
A309103 |
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