Isocyanate- and amine-functionalized polypropylene (PP) and polystyrene (PS) were prepared through grafting and copolymerization method. These compounds are used as precursors for PP-graft-PS (PP-g-PS) copolymers and reacted at the matrix interface of PP/PS blends. Functionalized polymer structures were characterized by H-1 NMR and FTIR spectroscopy. The effects of the synthesized compatibilizer on the rheological and morphological behavior of PP/PS blends were investigated systematically. Results showed that the functional polymer was successfully synthesized, and the additional two different compatibilizer systems dramatically decreased the size of the dispersed phase domains in PP/PS blends. Compared with the uncompatibilized blends, compatibilized blends exhibited a slightly higher crystallization temperature because the melting points of the blend components were not evidently affected by the addition of compatibilizer, as revealed by differential scanning calorimetry. The compatibilizer effect on the PP/PS blends was reflected through rheological property and dynamic mechanical analysis. POLYM. ENG. SCI., 55:614-623, 2015. (c) 2014 Society of Plastics Engineers