A facile yet robust approach to chemically fix an initiating group for atom transfer radical polymerization (ATRP) on various polymeric substrates is described Conventional free iadical copolymem ition was conducted with methyl methacrylate (M MA), 2-(2-bromoisobutyryloxy)ethyl methacrylate (an ATRP initiator-cal rying monomer, (ABEM), and 2((4-azidobenzoyDoxy)ethyl mcthacrylatc (a photoreactive phenylazide-carrying monomer, A BEM) in N,N-dimethylformamide at 75 degrees C, giving a random (suit': heal) copolymer. Thin films of the obtained copolymer were fabricated on poly(ethylene terephthalate) (PET) film surface by spin-casting a toluene solution of the tcrpolymer and were immobilized on the PET substi ate via UV-irradiation using the photoreactivity of the phenylazido units The surface-initiated ATRP (SI-ATRP) of poly(ethylene glycol) met hacrylate (PEG M A) mediated by a copper complex was carried out in water at 30 C in the presence of a sacrificial (free) initiator and the initiator-immobilized PET film as the solid substi ate The polymerization pi oceeded in a living fashion The molecular weight of free polymer increased with polymerization time while retaining low-polychspersity index, and more importantly, the thickness of the poly(PEG MA) graft layer Inc:leased as a function of polymerization time with a reduced graft density (sui face occupancy) as high as 0 Sin all examined time This initiator immobilization technique was applied to various polymeric substi ates including polystyrene, polypropylene, polyethylene, and polylacticle The fabrication of mici opattci ned polymei-bi ush sin faces was also demonstrated by photopatternina the initiator layei followed by si-A-rro