In this study, rubbery, bio-based thermoset polymers were synthesized from soybean oil (SO) and p-dinitrosobenzene (DNB) via an em reaction. Polymeric p-dinitrosobenzene (PDNB) was synthesized from p-quinone dioxime and was thermally depolymerized in the presence of SO. SO/PDNB polymers were synthesized by a two-stage polymerization. During the reaction, the role of different parameters such as mol ratio of SO and PDNB, preheating temperature of SO, polymerization time, and temperature were examined. Polymerization was followed by IR spectroscopy, and the polymers obtained were characterized by dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. The polymers have glass transition temperature ranging from -51.5 degrees C to -46.3 degrees C, whereas their storage moduli are between 430 and 210 MPa at -60 degrees C. Thermogravimetric analysis reveals that all of the polymers have temperatures Of maximum degradation around 500 degrees C. The crosslinked network structure of the polymers was investigated by swelling behavior and surface hardness test. Methyl oleate was used as a model Compound to examine the chemical structure of the products. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1925-1934, 2009