Ligand functional substrates

A ligand functional substrate comprising:

• a) a substrate, and
• b) a crosslinked ligand-functional alkenyl (co)polymer layer coated on the surface of the substrate, wherein the ligand-functional alkenyl (co)polymer comprises polymerized monomer units of the formula:
• wherein
• R1 is H or C1-C4 alkyl;
• R2 is a divalent alkylene having 1 to 20 carbon atoms;
• each R3 is independently H or C1-C4 alkyl;
• R4 is H, C1-C4 alkyl or —N(R3)2;
• R5 is H or C1-C4 alkyl or aryl;
• X1 is —O— or —NR3—,
• o is 0 or 1, and
• n is 1 or 2.