Synthesis And Properties Of PIPD And PPDA

Poly[2,5-dihydroxyl-1,4-phenylpyridine dimidazole](PIPD)is a kind of polymer fiber with rigid rod structure exhibiting large tensile strength,high modulus and heat-resistance.There are abundant hydrogen bonds between PIPD molecules chains exhibiting excellent compression resistance property.In this paper,2,5-dihydroxyterephthalic acid(2,5-DHTA)and 2,3,5,6-tetraminopyridine hydrochloride(TAP)were used as monomers to synthesize PIPD by condensation polymerization.Poly[N-(2,5-diamino-6-(Imino)pyridin-3-yl)-4-formyl-2,6-dihydroxybenzamide](PPDA)was prepared by condensation of 2,6-dihydroxy terephthalic acid(2,6-DHTA)and TAP hydrochloride monomers.And the properties of PPDA and PIPD were measured.(1)The monomer 2,5-DHTA was synthesized from 1,4-cyclohexanedione-2,5-dimethyl diformate(DMSS)by aromatization and hydrolysis reaction.It was characterized by ~1H-NMR and FT-IR after the purification procedure.And then it was reacted with TAP to prepare TD salt.PIPD polymer was synthesized by condensation of TD salt.The structure and properties of PIPD were analyzed by FT-IR,XRD,Raman,TG,and Ubbelohde viscometer.(2)The monomer 2,6-DHTA was synthesized from 3,5-dihydroxybenzoic acid by Kerbert-Schmidt reaction.It was characterized by ~1H-NMR and FT-IR after the purification procedure.PPDA polymer was synthesized by condensation of 2,6-DHTA with TAP hydrochloride.The structure and properties of PPDA were analyzed by FT-IR,XRD,Raman,TG,and Ubbelohde viscometer.The results showed that under the nitrogen atmosphere the maximum thermal decomposition temperature of PPDA is about 890℃and the residual is as high as 67%exhibiting good thermostability.(3)We designed and synthesized three model polymers named model 1,model 2 and model 3.The effect on the properties of PPDA polymer was studied by changing the reaction temperature.The structure and properties of three model polymers were confirmed by FT-IR,XRD,Raman,TG and Ubbelohde viscometer.As a result,the viscosity and thermostability of model polymers promoted with the increases of reaction temperature in 120℃-180℃.