4-(4'-Aminophenyl)-1,2,4-triazolidine-3,5-dione was reacted with 1 mol of acetyl chloride in dry N,N-dimethylacetamide (DMAc) at -15degreesC and 4-(4'-acetamidophenyl)-1,2,4-triazolidine-3,5-dione [4-(4'-acetanilido)-1,2,4-triazolidine-3,5-dione] (APTD) was obtained in high yield. The reaction of the APTD monomer with excess n-isopropylisocyanate,vas performed at room temperature in DMAc solution. The resulting bisurea derivative was obtained in high yield and was finally used as a model for the polymerization reaction. The step-growth polymerization reactions of monomer APTD with hexamethylene diisocyanate, isophorone diisocyanate, and tolylene-2,4-diisocyanate were performed under microwave irradiation and solution polymerization in the presence of pyridine, triethylamine, or dibutyltin dilaurate as a catalyst. Polycondensation proceeded rapidly, compared with conventional solution polycondensation; it was almost completed within 8 min. The resulting novel polyureas had an inherent viscosity in the range of 0.07-0.17 dL/g in dimethylformamide or sulfuric acid at 25degreesC. These polyureas were characterized by IR, H-1-NMR, elemental analysis, and thermogravimetric analysis. The physical properties and structural characterization of these novel polyureas are reported. (C) 2003 Wiley Periodicals, Inc.