A chromatography column, the column containing a packed bed of an ion exchange chromatographic packing material, the column comprising: a) support resin particles; and b) a copolymer comprising polymerized functional monomers that include a first ion exchange group monomer and a second ion exchange group monomer, where the first ion exchange group monomer and the second ion exchange group monomer are different, in which the first ion exchange group monomer is configured to have a first charge at a first pH, and the second ion exchange group monomer is configured to have a net neutral charge at the first pH, in which the first ion exchange group monomer is configured to have the first charge at a second pH, and the second ion exchange group monomer is configured to have a net neutral charge at the second pH, in which the first pH and the second pH are different, in which a mole percent of the second ion exchange group monomer is a mole amount of the second ion exchange group monomer divided by a summation of a mole amount of the first ion exchange group monomer and the mole amount of the second ion exchange group monomer, and multiplied by 100, the mole percent of the second ion exchange group monomer ranges from about 60% to about 99%, in which the copolymer is grafted to the support resin particles; wherein the first ion exchange group monomer comprises a styrene sulfonate, a vinyltoluenesulfonate, a 3-sulfopropyl methacrylate, a α-methylstyrenesulfonate, or a combination thereof; wherein the second ion exchange group monomer is a zwitterionic monomer; wherein the polymerized functional monomers further includes a third ion exchange group monomer; and wherein the first, second and third ion exchange group monomers each comprise a cation exchange group. a) support resin particles; and b) a copolymer comprising polymerized functional monomers that include a first ion exchange group monomer and a second ion exchange group monomer, where the first ion exchange group monomer and the second ion exchange group monomer are different, in which the first ion exchange group monomer is configured to have a first charge at a first pH, and the second ion exchange group monomer is configured to have a net neutral charge at the first pH, in which the first ion exchange group monomer is configured to have the first charge at a second pH, and the second ion exchange group monomer is configured to have a net neutral charge at the second pH, in which the first pH and the second pH are different, in which a mole percent of the second ion exchange group monomer is a mole amount of the second ion exchange group monomer divided by a summation of a mole amount of the first ion exchange group monomer and the mole amount of the second ion exchange group monomer, and multiplied by 100, the mole percent of the second ion exchange group monomer ranges from about 60% to about 99%, in which the copolymer is grafted to the support resin particles; wherein the first ion exchange group monomer comprises a styrene sulfonate, a vinyltoluenesulfonate, a 3-sulfopropyl methacrylate, a α-methylstyrenesulfonate, or a combination thereof; wherein the second ion exchange group monomer is a zwitterionic monomer; wherein the polymerized functional monomers further includes a third ion exchange group monomer; and wherein the first, second and third ion exchange group monomers each comprise a cation exchange group. <EOS>