In this study, functionalization of polystyrene (PS) (M,, = 2.5 X 105) was carry out with maleic anhydride in the presence of boron trifluoride dietyhletherade (BF3 OEt2) as catalyst and then functional PS was subjected to condensation reaction with phenyl hydrazine. The structures of both of them were determined by using FTIR, H-1-NMR, elemental analysis, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques. Some physical properties of these two products were investigated and the kinetic parameters of solid state decomposition reactions were determined from TGA curves. The intrinsic viscosity [eta] values of modified PS and condensation products (cPs) found to be 1.024 and 0.7036 dL g(-1) respectively. According to TGA, the weight losses of modified PS and cPs were found to be 84.03 and 81.86%, respectively, at 500 degrees C. (c) 2007 Wiley Periodicals, Inc.