A new grafted syndiotactic polystyrene (g-sPS), to be used as a compatibilizer for synctiotactic polystyrene (sPS)/polyadimide 66 blends, was prepared by the melting graft copolymerization of sPS and monomers composed of itaconic acid and dibutyl maleate with dicumyl peroxide as an initiator. The resulting g-sPS possessed a side-chain structure identified by IR spectra, and the results of mechanical testing show that a good impact strength and tensile strength were obtained for g-sPS at a 7.16-phr addition of monomer with a 3:1 proportion of dibutyl maleate and itaconic acid. Differential scanning calorimetry and scanning electron microscopy analysis indicated that the g-sPS maintained a high glass-transition temperature and a crystalline structure. (c) 2005 Wiley Periodicals, Inc.