Abstract: A polymer suitable for use in affinity chromatography comprising a polymer f an aminimide and a vinyl compound having at least one pendant halo-methyl group and the said polymer wherein an amine ligand which affords sites for binding in affinity chromatography is coupled to the polymer by reaction with a portion of the pendant halo-methyl groups and the remainder of said pendant halo-methyl groups are reacted with an amine containing a pendant hydrophilic group. The invention also comprises a method of coating a substrate with the above polymer and a method of fractionating mixtures by affinity chromatography employing the above polymer as an adsorbent.