Preparation And Properties Of Polyimides From Diamino Containing Hydroxyl Group

In this paper, three kinds of dinitro compounds are synthetized and then they are deoxidized into diamino ones by Pd/C-hydrazine hydrate system. They are 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, 3,3’-diamino-phenolphthalein and 3,3,3’,3’-tetramethyl-1,1’-spirobisindane-5,5’-diamino-6,6’-diol. At last, infrared spectrum analysis(FT-IR) and nuclear magnetic resonance hydrogen spectrum(1H NMR) are used to confirm the right target product.The different kinds of polyimides(PIs) are prepared from the sythsitic diaminos with various dianhydrides including 1,2,3,4-cyclobutanetetracarboxylic dianhydride(CBDA), 3,3’,4,4’-biphenyltetracarboxylic dianhydride(BTDA), 3,3’,4,4’-biphenyltetracarboxylic dianhydride(BPDA), pyromellitic dianhydride(PMDA), 4,4’-oxydiphthalic anhydride(ODPA) and 2,2′-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA) via chemical imidization. Infrared spectrum analysis(FT-IR), thermo-gravimetric analysis(TGA), differential scanning thermal analysis(DSC) and wide-angle X-ray diffractograms(XRD) are used to characterize the structures and properties of the polymers. It is concluded that the molecular chain of polyimides have formed imide rings and imide reaction is happened. Excepted the PI(b)-BTDA and PI(b)-ODPA, the glass transition temperatures(Tg) of synthetic polyimides are all over 300℃. The TGA thermogram of the HPI membranes was measured under nitrogen. Most of their weight loss at 5% and 10% are between 221℃~412℃ and 300℃~480℃ and char yield at 750℃ are between 40%~60%. The structures of polyimides are amorphous and they can dissolve in some polar solvents, such as DMF, DMAc, NMP and DMSO.The copolyimide is prepared from 9,9-bis(4-aminophenyl)fluorine(BAF), 9,9-bis(3-amino-4-hydroxyphenyl)fluorine and 2,2′-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA) by the traditional two-step method. FT-IR, TGA, DSC, XRD and gas permeation are used to characterize structures and properties of the copolymer. The copolymer is undissolved in such solvents as DMSO, DMF and DMAc. Copolyimide has a high resistance to chemical corrosion. PI has Tg values above 330℃. And the weight loss at 5% and 10% are about 495℃ and 550℃. Char yield at 750℃ of the copolymer is more than 60%. This type of copolymerization polyimide has the amorphous structure. The copolymer membrane shows good gas permeabilities and separations. It can be used as gas separation membrane.