The effect of magnetic field (MF) on the radical copolymerization of a series of water-soluble and ionic monomers is presented including acrylamide (AM), acrylic acid (AA), its ionized form acrylate (A(-)), and diallyldimethylammonium chloride (DADMAC). The following combinations have been studied: AM/AA, AM/A(-), AM/DADMAC, and AA/DADMAC. In addition to the MF, strong electrostatic interactions are present for the majority of monomer combinations and conditions. Although the monomer consumption rate (R-p) increased up to 65% applying a MF of 0.1 Tesla, the composition of the resulting copolymers was not affected under such conditions. Despite this increase of RP by MF, the electrostatic repulsion between ionic monomers and charged growing radicals dominates R, and governs the copolymer composition with and without MF. The order of the experimentally obtained reactivity ratios reflects the extent of electrostatic interaction: r(AM/AA) (1.41) < r(AM/A-) (3.10) < r(AA/DADMAC) (4.25) < r(AM/DADMAC) (6.95) and r(AA/AM) (2.20) > r(DADMAC/AA) (0.25) > r(A-/AM) (0.17) > r(DADMAC/AM) (0.03). Overall, weak MF offers to reduce the production time without modifying the product composition. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 373-383, 2009