In some aspects, the present disclosure pertains to chromatographic materials that comprise (a) a bulk material and (b) a zwitterionic polymer covalently linked to a surface of the bulk material, in which the zwitterionic polymer comprises one or more monomer residues that comprise an amide or urea moiety, a positively charged moiety, and a negatively charged moiety. Other aspects of the present disclosure pertain to chromatographic separation devices that comprise such chromatographic materials, to chromatographic methods that employ such chromatographic separation devices, and to kits that contain (i) such chromatographic materials and (ii) one or more chromatographic devices for containing such materials.