Synthesis And Imidization Kinetics Of Novel Polyimides

Polyimides are a kind of materials with high resistant property,excellent mechanical property and dielectric property,and they are widely used in the high technological areas of aerospace,photoelectric and microelectronic materials.However,most polyimides exhibit poor solubility and melting characteristics after imidization and some are difficult to form films.Therefore,to design novel polyimides with good processing property and thermal property is an urgent problem to be sovled in this field.In this article,4,4'-diamino-6-ethoxycarbonyl benzanilide?AECB?was synthesized by a three-step approach,and its structure was investigated by¹H-NMR,¹³C-NMR and FT-IR.Novel homopoly?amide-imide?s?PAMIs?and homopoly?benzoxazinone-imide?s?PBEIs?were prepared by temperature programming via the corresponding polyamic acids?PAAs?obtained through the reaction of AECB with 2,3,3',4'-biphenyl tetracarboxylic dianhydride??-BPDA?,2,3,3',4'-diphenylethertetracarboxylicdianhydride??-ODPA?and3,3',4,4'-benzophenone-tetracarboxylic dianhydride?BTDA?,respectively.Meanwhile,a seriesofnovelsilicon-containingcopoly?amide-imide?s?Si-PAMIs?and copoly?benzoxazinone-imide?s?Si-PBEIs?werepreparedfromcorresponding silicon-containing polyamic acid copolymers?Si-PAAs?via temperature programming by using?-BPDA,?-ODPA and BTDA as the dianhydride monomers,the AECB and1,3-bis?3-aminopropyl?tetramethyl disiloxane?DMS?as the diamine monomers.The imidization kinetics of the PAAs and Si-PAAs were investigated and compared by Differential Scanning Calorimetry?DSC?,and the kinetics parameters were simulated with two different kinetic models,Kissinger and Ozawa.The activation energies of Si-PAAs synthesized from?-BPDA were lower compared with the PAAs.According to the kinetics theory simulation and experiment test,the imidization process of PAA-3 and Si-PAA-3 were comfirmed as follows:165 ^oC/2h+215 ^oC/1h and 148 ^oC/2h+315 ^o C/1h,respectively.The structure and thermal performances of novel homopolyimides?PAMIs and PBEIs?and silicon-containing copolyimides?Si-PAMIs and Si-PBEIs?were investigated by FT-IR,XRD,DSC,TGA and DMA.The results indicated that homopolyimides showed a good thermal property and a poor film-forming property.All the PAMIs were amorphous,and the silicon-containing copolyimides were partially crystallized and the crystallization performance of silicon-containing copolyimides were improved because of the benzoxazinone structure.The film-forming ability and flexibity of Si-PAMIs were better than that of PAMIs,which were improved with the increase of silicon-containing diamine increasing.