Synthesis And Characterization Of Polyimide Monomers And Corresponding Polymers

This thesis gave a review on general properties,recent development and modification methods of polyimides.Based on this review and theoretics of the molecular design,an ideal was presented to introduce alkyneyl group,ether linkage, flexible fat chain and sulfuryl group and etc.into the molecular main chain for the modification of polyimide.The coupling reactions,such as Sonogashira reaction and the Williamson reaction and the like,were the main methods used to synthesis these new monomers for obtaining modified polyimides.The newly synthesized monomers containing the designed special functional groups were characterized by using IR, HNMR,DSC,LC and so on.The polyamic acid(PAA) synthesized by the1,4-bis[β-(p-aminophenyl) ethyl] benzene(p-APEB) and 3,3',4,4'-biphenyltetracarboxylic dianhydride(BPDA) via a condensation polymerization at low temperature.The polyamic acid was converted into polyimide by high temperature curing.IR,DSC,TGA and tensile tester was used to characterize the newly synthesized polyimide.This thesis mainly consists of the following six parts.The first is to synthesis the organic intermediates 1,4-diethynylbenzene and 1,3-diethynylbenzene from starting materials,1,4-dibromobenzene,1,3-dibromobenzene and 2-Methyl-3-butyn-2-ol using Songashria reaction in two steps.The effects of the molar ratio of the starting materials,the reaction temperature and the mount of water in the solvent and the methold of the purification on the yield of the resulting products were studied and dicussed.It paved a way to synthesize the monomers for synthesizing the polyimide containg alkynyl group in main chain.The second is to synthesis the monomer diamine 1,4-bis[β-(p-aminophenyl)ethyl] benzene(p-APEB) from the starting materials,1,4-diethynylbenzene and the 1-bromo-4-nitrobenzene using Songashria reation in two reaction steps.The effects of the halogen substitutes,acid-bindings,solvent,reaction temperature and catalysts on the resulting yield were studied and discussed.The third is to synthesis the monomer dianhydride 1,4-bis[β-(ρ-phthalic anhydride) ethynyl]benzene from the starting materials,1,4-diethynylbenzene and 4-bromophthalic anhydride using Songashria reaction by a three-step reaction.The effects of the halogen substitutes,acid-bindings,solvent,reaction temperature and catalysts on the yield of the resulting product were studied and discussed.The forth is to synthesis the diamine monomers,1,6-,1,5-,1,4-,1,3-,and 1,2-di (4'-aminophenoxy)alkane from the starting materials,1,6-,1,5-,1,4-,1,3-,and 1,2-dibromoakanes andρ-nitrophenol using Williamson reaction by a two-step reaction.The effects of the used amount of KOH,the water in solvent,the halogen substitutes and the purification methods on the yield of resulting products were studied and discussed.The fifth is to synthesis the diamine monomers,1,4-bis(4'-aminophenoxy)phenylene, 4,4′- bis(4″-aminophenoxy)biphenylene,2,2-bis[4′-(4″-aminophenoxy)-phenyl] propane,4,4″-di[(4′-aminophenoxy)phenyl]sulfone from the starting materials,hydroquinone,diphenol,2,2-bis(4′-hydroxyphenyl)propane, 4,4′-dihydroxydiphenyl sulfone and p-nitrophenol using Williamson reaction by two-step reactions.The effects of the amount of K₂CO₃,solvents,water amount in solvent and the purification methods on the resulting yields of these products were studied and discussed.The sixth is to synthesis the polyamic acid(PAA) from monomer 1,4-bis[β-(p-aminophenyl) ethyl]benzene(p-APEB) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA) by a polycondensation at low temperature.The corresponding polyimide was obtained by an imidization process of curing the above PAA at high temperature.The resulting polyimide film was characterized by IR,TGA,DSC and tensile tester.The results showed the as-prepared polyimide has a melting temperature of 233℃,glass transition of 193℃and thermal degradation temperature of 521℃.The tensile strength modulus is respectively 211MPa and 5.36 GPa.