| Summary: | 碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 99 === Two new asymmetric and aromatic diamines, 2-bromo-4,4’-oxydianiline (Br-ODA 6) and 2,2’,6-tribromo-oxydianiline (TrB-ODA 7), have been synthesized by oxidation, bromination in the presence of different amount of N-Bromosuccinimide (NBS) then reduction of 4,4’-oxydianiline (4,4’-ODA). Based on diamine (6) and (7), a series of asymmetric polyimides (PI 10 and PI 11) were prepared by three different dianhydrides in refluxing m-cresol containing a catalytic amount of isoquinoline, respectively. The resulting polyimides, except Br-ODA/PMDA, are soluble in the m-cresol without precipitated during polymerization. These polyimides, especially PI 11, showed enhanced solubilities compared to those derived from 4,4’-ODA and corresponding dianhydride. The PI 11a derived from the very rigid pyromellitic dianhydride (PMDA) and TrB-ODA (7) can be soluble in THF, DMF, DMAc, DMSO and NMP in ambient temperature. In the 1H-NMR spectrum of the PI 11a, the protons of pyromellitic moiety shows three different chemical shifts are attributed to the fact that there are three different repeating unit isomers. The incorporation of the asymmetric bromide substituents is an effective way to increase the interchain distance and decrease in the intermolecular force and packing ability of resulting polymers. Thus, these polyimides also exhibited good thermal stability. Their glass transition temperatures were ranged from 297 to 333℃ and coefficient of thermal expansion were 27～56μm/(m℃) measured by thermal mechanical analysis (TMA). The temperature at 5% weight loss (Td 5%), determined by thermal gravimetric analysis (TGA) in nitrogen atmosphere, were in the range of 467 to 529℃. In addition, another two diamines containing asymmetric phenyl groups were synthesized by using Suzuki coupling based on asymmetric bromide diamines. The preliminary results on the properties of polyimides derived from these two phenyl substituted asymmetric diamines were also reported.
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