Two complementary tandem strategies based on the one-pot combination of click chemistry and atom transfer radical polymerization (ATRP) are studied. Initially, functionalized random copolymers are obtained by copolymerization of methyl methacrylate and propargyl methacrylate simultaneously to the click chemistry coupling of a monofunctional azide. Then, an approach based on the copolymerization of methyl methacrylate and 11-azido-undecanoyl methacrylate simultaneously to the click chemistry coupling of a monofunctional alkyne is also investigated. For both the approach, polymerization and click chemistry coupling are catalyzed by CuBr and bipyridine (Bipy) in diphenylether at 90 degrees C. The [Bipy]/[CuBr] ratio is varied from 2 to 25 and the ratio of functionalized comonomer from 20 to 70 mol %. Both the tandem strategies proceed with good yields (50-80%) and allow a good control over the characteristics of the resulting random copolymers and macromolecular brushes (M-n similar to 15,000-40,000 g/mol and PDI similar to 1.3-2.0) as well as quantitative click functionalization as characterized by H-1 NMR and size exclusion chromatography analyses. Although the click process is generally completed at the early stage of the process, the rate of polymerization depends on the amount of bipyridine involved. It was found that extending most of the polymerization process out of the click reaction regime results in a better control of the polymerization, preventing the significant occurrence of side reactions. (C)2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47:3803-3813, 2009