Polymer brushes that present side chain functional reactive groups are attractive platforms for the development of functional surface coatings. From the wide spectrum of possible postpolymerization modification reactions, thiol-based conjugation chemistries are particularly appealing as they can be performed reagent-less under mild conditions and can allow the site-selective conjugation of biomolecules. This manuscript reports a direct approach for the preparation of maleimide-functionalized polymer brushes. These brushes were obtained by surface-initiated atom transfer radical copolymerization of poly(ethylene glycol) methacrylate and a furan-protected, maleimide containing monomer, followed by a thermally induced retro DielsAlder reaction to unmask the maleimide groups. The feasibility of these brushes to serve as a platform for postpolymerization functionalization was explored in a series of model experiments using a variety of low molecular weight thiols, including a fluorescent dye and a thiol-modified biotin-derivative. The biotinylated brushes were subsequently used for the immobilization of streptavidin-coated quantum-dots. The copolymer brushes presented in this manuscript are attractive since they combine the nonbiofouling properties of the poly(ethylene glycol) methacrylate monomer with the chemoselective reactivity of the maleimide containing monomer, which makes them an attractive platform, e.g., for the immobilization of biomolecules.