Study on synthesis of polyamic acid and polyimide under microwave irradiation

The copolycondesation type polyamic acid(PAA) was synthesized by using pyromellitic dianhydride(PMDA) and 3,3′,4,4′-Benzophenonetetracarboxylic dianhydride(BTDA) as the dianhydride monomers,4,4′-oxydianiline(ODA) as the diamine monomer under microwave irradiation in dimethylformamide(DMF).Then PAA came into being the polyimide(PI) through an imidization process.The structure and performance of the polymer were characterized by FT-IR,1H NMR,viscosity and TG analysis.The results showed that under microwave irradiaton,the intrisic viscosity and the yield of PAA were raised,and the reaction time was shortened.The FT-IR spectra of the polymer showed that there were PI's characteristic peaks at 1 778 cm-1 and 1 723 cm-1.Thermogravimetric curve indicated that the obtained polyimide began to lose its weight at 535 ℃ and the thermal decomposition temperature under N2,at which the losed weight was 10%,was 587 ℃.