Radical polymerization was used to synthesize three copolymers of [3-(methacryloylamino)propyl]trimethylammonium chloride and methacrylic acid [P(MPTA-co-MA)]; three copolymers of MPTA and 2-acrylamido-2-methyl-1-propane sulfonic acid [P(MPTA-co-APSA)], which had different feed monomer mole ratios but a constant total number of moles, (0.03 mol); and the homopolymers poly(MPTA), poly(MA), and poly(APSA). The yields for all homopolymers and copolymers were over 70 and 90%, respectively. All products were dissolved in water, purified, and fractioned by an ultrafiltration membrane with different exclusion limits of the molecular weight (3,000, 10,000, 30,000, and 100,000 g mol(-1)). All fractions were lyophilized. The polymeric materials were characterized by FTIR and H-1-NMR spectroscopy. The metal ion interaction with the hydrophilic polymers was determined as a function of the pH and the filtration factor. It was dependent on the pH, type of ligand group, and charge of the metal ion. (C) 2003 Wiley Periodicals, Inc.