4-(4'-Aminophenyl)urazole (AmPU) was prepared from 4-nitrobenzoic acid in six steps. The reaction of monomer AmPU with n-isopropylisocyanate was performed in N,N-dimethylacetamide solutions at different ratios, and the resulting disubstituted and trisubstituted urea derivatives were obtained in high yields and were finally used as models for polymerization reactions. The step-growth polymerization reactions of AmPU with hexamethylene diisocyanate, isophorone diisocyanate, and toluene-2,4-diisocyanate were performed in N-methylpyrrolidone solutions in the presence of pyridine as a catalyst. The resulting novel polyureas had inherent viscosities of 0.11-0.18 dL/g in dimethylformamide at 25degreesC. These polyureas were characterized with IR, H-1-NMR, elemental analysis, and thermogravinietric analysis. Some physical properties and structural characterization of these novel polyureas are reported. (C) 2003 Wiley Periodicals, Inc.