Synthesis and characterizations of organosoluble aromatic copolyimides

A series of aromatic copolyimides was successfully synthesized from the commercial pyromellitic dianhydride (PMDA) with the commercial diamine p-phenyldiarnine (PDA) and the diamine 4,4'-methylenebis-(2-tert-butylaniline) (MBTBA) specially designed by ourselves. The copolyimides were characterized by IR, NMR, GPCIUV-Vis,TGA and DMA. The copolyimide was precipitated in m-cresol in the polymerization process when the molar ratio of MBTBA and PDA was lower than 6/4. The number-average molecular weight of the soluble copolyimides measured by GPC was larger than 4.0 x 10(4) and the polydispersity index was higher than 1.5. Only one glass transition temperature of these copolyimdies was detected around 360 degrees C by DMA. The copolyimides did not show appreciable decomposition up to 500% under N-2, and the thermal stability of the copolyimide increased a little with the introduction of the PDA into the polymer chains.