A reactive polymer brush containing alkoxyamine units in the side chains, when heated with an alkoxyamine-terminated fluorinated nongrafted polymer, gave a grafted copolymer brush by a radical crossover reaction of alkoxyamine units The fluorinated grafted copolymer brush could be converted back to the parent polymer brush upon treatment with an excess of low-molecular alkoxyamine The reversible change in the surface properties of the brush was confirmed by X-ray photoelectron spectroscopy and contact angle measurements