In this study a novel and simple route for the synthesis of the iodine isocyanate (INCO) adduct of soybean oil triglycerides is described. Soybean oil iodo isocyanate (ISONCO) was synthesized by the reaction of iodine isocyanate and soybean oil at room temperature. ISONCO was then polymerized With polyols, such as, castor oil, pentamethylene, glycol, and glycerol to give the corresponding polyurethanes and with polyamines, Such as, ethylene diamine, hexamethylene diamine, and triethylene tetramine to give corresponding polyureas. The structures of the monomer and the polymers were determined by FTIR and H-1-NMR analyses. Thermal properties of the polymers were determined by DSC and TGA. Thermal degradation of the polyurethanes started at 150 degrees C. Stability of the polyureas was higher than polyurethanes. Almost all polymers showed a T-g around -50 degrees C. The mechanical properties of the polymers were determined by tensile tests. Among the polymers synthesized, castor oil polyurethane showed the highest elongation at break and the lowest tensile strength of 140 KPa. The highest tensile strength of 900 KPa was observed in the pentamethylene glycol polyurethanes. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2433-2440, 2010