Polymer surface modification method comprising the steps of first forming a surface of primary reactive end groups tethered to the polymer chain ends during fabrication of an article, and then modifying the reactive surface with bio-active molecules, hydrophilic and hydrophobic monomers, oligomers, or polymers to attain specific surface properties. Alternatively, a multifunctional coupling agent can be used to couple the primary reactive group to a second reactive group capable of reacting with a functional group associated with bio-active molecules, hydrophilic and hydrophobic monomers, oligomers, and polymers to attain specific surface properties. The invention involves bringing reactive endgroups to the surface with surface active spacer attached to the polymer chain end. The surface active spacer allows the migration and enrichment of reactive end groups to the surface during fabrication. The invention provides medical devices having a bio-interface with anti-thrombogenic properties, lubricity, selective adsorption, and antimicrobial properties.