| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 96 === In this research, we developed a divergent scheme of synthesizing up to second generations of polyimide dendrimers (PI Dendrimers) based on one common ABB’ Intermediate (2) as core through repetitive reactions of hydrogenation and imidization using low-cost reagents.
The core of our overall scheme relied upon the synthesis of 3-(2,4-dinitrophenoxy) phthalic anhydride (2) .(2) was obtained by the autoxidation of 2,4-dinitrophenyl-3,4-dimethyl phenyl ether (1), which was readily accessible from 3,4-dimethyl phenol and 1-Chloro- 2,4-dinitrophenol by a base-initiated replacement reaction. The yield of autoxidation of (2) has been enhanced to 84~87% yield in this study by carefully adjusting cobalt acetate/manganes acetate/sodium bormide catalysts ratio in acetic acid. It was found that the optimal condition is to carry out the autoxidation at 140 ℃ with the concentration ration between Co(OAc)2/ Mn(OAc)2 /NaBr of 0.65:0.65:0.50 (wt%) in 9.09 % weight concentration.
Imidization (2) of was carried out with aniline in the first step followed by hydrogenation to form the tri-imide-D0 bearing di-amine-D0 can then go through the same sequence of di-imidization with two moles of (2) and then hydrogenation of the tetra-nitro-D1, and this resulted in Penta-imide bearing tetra-amine-D1 (7). Finally, (7) went through the same sequences of imidization and hydrogenation to form the nonyl-imide-D2 bearing octa-amine-D2.
Although this straight forward divergent synthesis could go on repeatedly in theory to form high PI dendrimers, we found that the hydrogenation of nitro-groups became sluggish in ethyl acetate solution as the generations of PI dendrimers grew. It was found that 1,4-dioxane on particularly a good solvent to use in hydrogenation of high generations of PI polynitro-dendrimers because of its solvating power, which allowed the hydrogenation to be done at low-temperature without other complications.
All PI dendrimers synthesized show their melting points between 250℃-290℃and could be dissolved readily in solvents such as NMP, THF and CHCl3.The thermal characteristics and potential utilities of the dendrimers are still being investigate.
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