Abstract

This work reports the synthesis of six new polyimides obtained by the reaction of two novel diamine monomers: methyl 4-(3,5-diaminobenzamido)benzoate and dimethyl 5-(3,5-diaminobenzamido)isophthalate, bearing one or two methyl ester groups in their phenyl rings, respectively, with three known dianhydrides, 4,4′-(hexafluoroisopropylidene) diphatalic anhydride (6FDA), 4,4′-(dimethylsilanediyl) dipthalic anhydride (SiDA) and 4,4′-oxydiphthalic anhydride (ODPA). The polyimides were synthesized using the “two-step” method, which first involves forming a poly(amic acid) precursor that is subsequently cyclodehydrated to form the imide linkage. The yields were higher than 95% in all cases, and the structural characterization was performed by spectroscopic techniques like FT-IR, 1H, 13C, and 29Si NMR. In addition, the effect on the solubility in common organic solvents and thermal and gas transport properties of these polyimides were studied as a function of the nature of the respective side group and the dianhydride used.