Functionalized copolymers and use thereof

A process for separating aggregated proteins from monomeric proteins in a biological solution, the process comprising:

• providing at least one filter element having a contacting surface, wherein the filter element comprises filter media comprising:
• a) a porous substrate;
• and
• b) a copolymer covalently attached to the porous substrate, the copolymer comprising a hydrocarbon backbone and a plurality of pendant groups attached to the hydrocarbon backbone, wherein:
• 1) Each of a first plurality of pendant groups comprises:
• (a) at least one acidic group or salt thereof;
• and
• (b) a spacer group that directly links the at least one acidic group or salt thereof to the hydrocarbon backbone by a chain of at least 6 catenated atoms;
• and
• 2) each of a second plurality of pendant groups comprises:
• (a) at least one acidic group or salt thereof;
• and
• (b) a spacer group that directly links the at least one acidic group or salt thereof to the hydrocarbon backbone by a chain of at least 6 catenated atoms;
• and
• wherein the first plurality of pendant groups are different than the second plurality of pendant groups;
• and
• wherein a mole ratio of the first plurality of pendant groups to the second plurality of pendant groups is in a range of 95:5 to 5:95;
• and
• allowing an initial biological solution to contact the contacting surface of the filter element under conditions effective to separate the aggregated proteins from the monomeric proteins such that a final biological solution includes purified monomeric proteins.