An investigation of graft polymerization to determine the potential of a starch-bonded acryloyl group as a suitable coupling agent with vinyl monomers was carried out. In this case, potassium persulfate was used as a free-radical initiator using water as the reaction solvent for further graft polymerization. This work revealed the ability of water as a reaction medium; perhydroxyl and hydroxyl radicals were easily formed from persulfate to produce free radicals to activate the styrene monomer towards grafting with acryloylated potato starch. The graft copolymers were characterized by FT-IR spectroscopy and further confirmed using saponification. The analysis results showed the grafted potato starch with the styryl chain afforded protection to the ester bond, which resisted the alkaline hydrolysis. (C) 2005 Wiley Periodicals, Inc.