We synthesized copolymers based on 2-hydroxyethylmethacrylate and N-maleoylglycine by varying the monomer feed composition. The copolymers were characterized by Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetry/differential scanning calorimetry as the thermal analysis method. The thermograms showed that the polymers degraded in a single-stage process. For the hydrogels of poly(2-hydroxyethymethacrylate) and poly(2-hydroxyethylmethacrylate-co-N-maleoylglycine) [poly(HEMA-co-MG)], swelling behaviors were investigated by the immersion of the gels in solution at pH's of 3, 5, and 7. The swelling studies were performed with and without ionic strength. The copolymer composition had a significant effect on the equilibrium swelling behavior of poly(HEMA-co-MG). With those soluble copolymer fractions, we obtained a low conversion (<30%); the monomer reactivity ratios were estimated by the Kelen-Tudos linear method. The data indicated that poly(HEMA-co-MG) was a random copolymer. (c) 2005 Wiley Periodicals, Inc.