The chelation of poly(maleic anhydride-alt-acrylic acid) [poly(MA-alt-AA)] with nickel (II), cadmium (II), and copper (II) ions was carried out under various pH conditions. Polychelates were prepared by precipitation from the aqueous solutions of metal salts at different pH values. The effects of metal salts (NiCl2.6H(2)O, CdCl2.2H(2)O, CuCl2.2H(2)O) on the degree of crystallinity of poly(MA-alt-AA) were investigated by X-ray diffraction spectroscopy at different pH values. The degree of crystallinity was found to be in the following order: Cd(II)-polychelate > Cu(II)-polychelate > Ni(II)-polychelate at pH 6.36; this result was also supported by gravimetric studies. (C) 2003 Wiley Periodicals, Inc.