SYNTHESIS AND PROPERTIES OF SOLUBLE POLYMIDES CONTAINING BENZIMIDAZOLE MOIETY

A new aromatic diamine monomer, alpha,alpha-bis(4-amino-3,5-dimethylphenyl) phenylmethane (BADP),was synthesized via a straightforward one-step procedure with high yield. FTIR and H-1-NMR were employed to confirm the designed structure. In order to maintain the excellent thermal properties and improve the solubility of polyimides, a series of aromatic polyimides were successfully synthesized via one-step polymerization method in anhydrous N-methyl-2-pyrrolidone (NMP) by a reaction of 2-(4-aminophenyl)-5-aminobenzimidazole (BIA), the synthesized BADP and one of four dianhydrides (PDMA, BPDA,BTDA and ODPA). The structures of copolyimides were confirmed by FTIR,showing the characteristic peaks of polyimides at 1780,1720 and 725 cm(-1). The UV-Vis measurements indicated that the cut-off wavelengths were at 360 similar to 380 nm without consideration of relatively weak transmittance in the range of 310 similar to 360 nm. As we expected, the polyimides exhibit excellent solubility, and can be dissolved in normal solvents such as NMP, DMAc or CHCl3. The soluble polyimides show a relatively higher glass transition temperature (T-g>410 degrees C) measured by dynamic mechanical analysis (DMA) and a high initial decomposition temperature (T-g>500 degrees C) in TGA and more than 55 wt% residues at 900 degrees C under nitrogen atmosphere. Moreover, the tensile strength of polyimides is 61 similar to 100 MPa. The soluble polymers can be used as high performance resins or processed into high performance fibers.