A water-soluble cationic flocculant, a copolymer of acrylamide (AM) and acryloylamino-2-hydroxypropyl trimethyl ammonium chloride (AMHP), was synthesized through dispersion polymerization method in aqueous ammonium sulfate ((NH4)(2)SO4) Solution. The polymerization was initiated by gamma-radiation using poly(2-methylacryloylxyethyl trimethyl ammonium chloride)(PDMC) as the stabilizer. The obtained copolymer was characterized by using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), colloidal titration and optical microscopy. Its flocculation properties were evaluated with 0.25 wt% kaolin suspensions using a standard jar test. The zeta potential of supernatant at different flocculant dosage was simultaneously measured. The results demonstrate the superiority of the copolymer over the commercial polyacrylamide as a flocculant. (C) 2008 Elsevier B.V. All rights reserved.