| Summary: | 碩士 === 國立中興大學 === 化學工程學系 === 89 === Abstract
In the first part of this study, a linear electro-optical (EO) measurement was set up by a simple reflection method. A laser beam aims on the glass substrate at an incident angle q. The incident laser beam is linearly polarized with a 45o polarization angle in respect to the incidence plane so that the parallel (p wave) and perpendicular (s wave) polarized optical fields have equal amplitudes. The beam is transmitted through the ITO-coated substrate, the thin film of NLO material, and then reflected by a gold film. The reflected beam propagates through a Soleil-Babinet compensator, an analyzer and then into a detector. A sinusoidal voltage is applied on the NLO film and the modulation of the laser beam is measured using a lock-in amplifier. Using helium-neon laser (λ = 632.8 nm), an EO coefficient of 30.8 pm/V at the wavelength of the He-Ne laser was obtained for a z-cut LiNbO3 crystal, which is comparable to that reported in literature. The set-up of EO-coefficiency measurement was estabilished and it’s operation was confirmed.
For the second part of this study, 5,5’-diamino-2,2’-bipyridine was synthesized for preparing high performance polyimides. The polymers can be coordinated with nickel containing complexes such as (NH3)2Ni(mnt) and Ni(tfd)2, and coordination nickel complex-contained polyimides, PI-Ni(mnt) and PI-Ni(tfd) were obtained.
These metal-coordinated polymeric materials exhibit the improved solubility and mechanical property (high Tg's above 200℃). However, the Td’s are lower than those of the pristine polyimides.
A metal-complex coordinated polyimide copolymer coPI50.3, was analyzed by UV-vis and NMR because of its better solubility. An absorption maximum was found at 809 nm. This observation implies the existence of anion of Ni(tfd)- . Moreover, the signals due to the hydrogen atoms of bipyridine ring were not detected by 1H NMR. To further clarity the chemical structure of the metal-complex coordinated polyimide, a series of model compounds were synthesized, and they were analyzed by UV-vis, 1H NMR, and elemental analysis. It was found that a paramagnetic six-coordinated Ni2+ center with two Ni(tfd)- as counter ions presents in the nickel-contained polyimides as well as model compounds. The previously expected second-order NLO active four-coordinated square planar bonding structure was not formed. This study also confirmed that, except the NO2-contained bipyridine complex Ni(5NO2bipy)(tfd), nickel metal complexes are in form of second-order NLO inactive six-coordination in either model compounds or polymer.
To investigate the electro-optical property of the push-pull nickel complex contained in bulk material, a guest-host system based on commercially available polysulfone and Ni(5NO2bipy)(tfd) [doping level = 10 wt%] was prepared. An EO coefficient r33 of 0.7 pm/V was obtained after poling at 165 ℃ (7 kV) for 10 minutes.
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