Disclosed are composite materials and methods of making them. The composite materials comprise a support member and a cross-linked gel, wherein the cross-linked gel is a polymer synthesized by thiol-ene or thiol-yne polymerization and cross-linking. The cross-linked gel may be functionalized by a thiol-ene or thiol-yne grafting reaction, either simultaneously with the polymerization or as the second step in a two-step procedure. The composite materials are useful as chromatographic separation media.