Activation-free copolymeric films possessing high selectivity to target proteins and low biofouling background are prepared via controlled radical polymerization. The copolymeric films are generated by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) of N-acryloxysuccinimide (NAS) and oligo(ethylene glycol) methyl ether methacrylate (OEGMEMA) by controlling the molar feed ratio of the two monomers. The formation of copolymeric films is characterized by ellipsometry, contact angle goniometry, FTIR spectroscopy, and X-ray photoelectron spectroscopy. The prepared copolymeric films are biotinylated without an activation step. Biotin-streptavidin association is employed as a model system to investigate both selective binding and the relevant signal-to-noise (S/N) ratio. When the molar feed ratio of NAS and OEGMEMA is 2:8, the copolymeric film is optimized to give the highest S/N ratio (339.8) according to surface plasmon resonance studies. The highly selective bioconjugation is used to generate micropatterns of rhodamine-conjugated streptavidin on the copolymeric film. (C) 2016 Wiley Periodicals, Inc.