Copolymers of 4-vinylpyridine : divinylbenzene with various degrees of crosslinking have been obtained as precursors for ionic polymers. To this end, addition reactions of the 4-vinylpyridine : 8% divinylbenzene copolymer to electrophylic ethylenic compounds, such as acrylamide, acrylonitrile, and methyl vinyl ketone in the presence of HCl have been performed; the resulting ionic polymers contain, besides ammonium quaternary groups, other functional groups such as amide, nitrile, and ketone. The quantitative iron retention from aqueous Fe₂(SO₄)₃ solutions was determined photocolorimetrically for both 4-vinyl-pyridine : divinylbenzene copolymers and the synthesized ionic polymers. IR and Mössbauer spectroscopy were used to determine the state of the Fe(III) ions in the tridimensional networks. As expected, in 4-vinylpyridine : divinylbenzene copolymers, Fe(III) ions are retained by nitrogen atoms-Fe(III) complexes. The electronic state of metal ions hardly depends on the crosslinking degree. In the ionic polymers, the Fe(III) ions are retained through ionic exchange as the R₄N⁺[Fe₃(SO₄)₂(OH) ₆]^- complex anion. The functional amide, nitrile, and ketone groups, although containing atoms able to form donor-acceptor bonds, do not take part in the complexation.