Study On Preparation And Properties Of PIPD

Poly{2,6-dimidazo[4,5-b:4,5-e]pyridinylene-1,4（2,5-dihydroxy）phenylene},abbreviated as PIPD, is a kind of excellent polymer. Due to the presence of two-way hydroxy in the molecular structure,PIPD has the ability of forming strongintermolecular and intramolecular hydrogen bonds between the molecules andadjacent chains. PIPD fiber have the superior compressive and heat resistance,aging resistance and Other properties are also more prominent. Therefore,it will bea good prospect of application in the future.In this study,2,6-diaminopyridine（DAP） was nitrated to prepare2,6-diamino-3,5-dinitropyridine （DADNP） by oleum and fuming nitric acid in an one-stepmethod. After purified by DMSO, DADNP was used to synthesized2,3,5,6-tetraaminopyridine hydrochloride salt（TAP3HCl H₂O） by catalyzedhydrogenation. TAP3HCl H₂O was characterized by FT-IR,1H-NMR,13C-NMR,HPLC and elemental analysis and its purity was up to above99.8%afterpurification;2,5-dihydroxyterephthalic acid （DHTA） was prepared from thearomatization and hydrolytic reaction of dimethyl succinoylsuccinate, and itspurity was up to above99.9%after purification. The products were characterisedby FT-IR, HPLC,1H-NMR,13C-NMR, etc.The preparation of TD salt was studied and characterized by FT-IR, TG,1H-NMR, and element analysis. Off HCl Polycondensation was discussed.The optimalroute of TD salt polymerization was confirmed through the orthogonalexperiments. The key factors influencing the polymerization reaction wereinvestigated systematically. The PIPD polymer were analyzed by FT-IR, RamanSpectrum,XRD,TG, Ubbelohde viscometer and it have two-dimensional orderedcrystalline structure and good heat resistance.