A rapid way assisted by microwave irradiation was proposed to synthesize poly[2,2＇-（m-phenylene）-5,5＇-bibenzimidazole]（PBI） and poly（2,5-benzimidazole）（ab-PBI）.Synthesis of PBI in polyphosphoric acid is conducted for 20 h or even more.Under microwave irradiation,the polycondensations could be completed in polyphosphoric acid within 3 h from 3,3＇-diaminobenzidine tetrahydrochloride（DAB·4HCl·2H2O） and isophthalic acid for PBI,and from 3,4-diaminobenzoic acids（DABA） for ab-PBI,respectively.The conditions for the polymerization including the power of microwave irradiation,temperature,heating time,and concentrations of the reactants in polyphosphoric acid were optimized.The inherent viscosity of the polymers in concentrated sulfuric acid at 30 ℃ was 0.9766 dL/g for PBI,and 0.6480 dL/g for ab-PBI,respectively.Characterization of the polymer products was made by nuclear magnetic resonance（1^H NMR）,Fourier transform infrared spectra（FTIR） and thermogravimetric analysis（TGA）.
HE Rong-huan SUN Bao-ying YANG Jing-shuai CHE Quan-tong
