The free-radical copolymerization of N-phenylmaleimide (N-PhMI) with acrylic acid was studied in the range of 25-75 mol % in the feed. The interactions of these copolymers with Cu(H) and Co(H) ions were investigated as a function of the pH and copolymer composition by the use of the ultrafiltration technique. The maximum retention capacity of the copolymers for Co(H) and Cu(H) ions varied from 200 to 250 mg/g and from 210 to 300 mg/g, respectively. The copolymers and polymer-metal complexes of divalent transition-metal ions were characterized by elemental analysis, Fourier transform infrared, H-1 NMR spectroscopy, and cyclic voltammetry. The thermal behavior was investigated with differential scanning calorimetry (DSC) and thermogravimetry (TG). The TG and DSC measurements showed an increase in the glass-transition temperature (T-g) and the thermal stability with an increase in the N-PhMI concentration in the copolymers. T-g of poly(N-PhMI-co-AA) with copolymer composition 46.5:53.5 mol % was found at 251 degrees C, and it decreased when the complexes of Co(H) and Cu(H) at pHs 3-7 were formed. (c) 2005 Wiley Periodicals, Inc.