A comb-like surfactant polymer for changing the surface properties of biomaterials is described. The surfactant polymer comprises a polymeric backbone of repeating monomeric units having functional groups for chemically attaching to side chains, a plurality of hydrophobic side chains attached to the backbone via the functional groups and a plurality of hydrophilic side chains chemically attached via functional groups to the polymeric backbone. The hydrophilic side chains providing anti-thrombogenic properties to the surfactant. An antimicrobial agent selectively attached to some hydrophilic side chains thereby providing additional antimicrobial properties to the surfactant. The surfactant polymer may be applied to the surface of medical devices to reduce the surfaces thrombogenicity and decrease the number of microorganisms on the surface.