The “Sharpless-type click chemistry” has attracted considerable attention during the past decade since it provides an easy way to obtain complex macromolecular architectures such as linear, star, cyclic, graft polymers, and copolymers as dendrimers. However, the polymers with azide group used in “Sharpless-type click chemistry” are difficult to be preserved due to their photosensitivity and thermal instability, whichmeans special care should be taken. Another type of click chemistry, the Diels-Alder reaction (DA) [4+ 2] system, provides a coupling strategy using a diene and dienophile by intraor intermolecular reaction. This shows great potential based on the macromolecular chemistry particularly providing new materials. However, the maleimide or anthracene end-functionalized polymers generally require multistep synthesis and purification. Monteiro also reports a radical coupling method to make highmolecular-weightmultiblock copolymers from a difunctional PS, by an outer-sphere electron transfer mechanism. Recently, our group found macroradicals, generated in the presence of metal catalyst and conjugates, could be instantly captured by the 2,2,6, 6-tetramethylpiperidinyl-1-oxy (TEMPO) group in another polymer chain by formation of alkoxyamine linkage with high effiency. This kind of reaction is named as “atom transfer nitroxide radical coupling” (ATNRC) reaction. Generally, CuBr and N,N,N0,N0 0,N0 0-pentamethyldiethylenetriamine (PMDETA) were used as the catalyst to generate macroradicals in ATNRC under a relatively high temperature, which could cause side reactions such as cross-link and chain transfer. Some polymers obtained from active monomers, such as methacrylic esters, cannot be conducted in ATNRC due to the significant β-hydrogen transfer from the macroradicals. To overcome these disadvantages, the condition ofATNRC should be optimized. Percec reported that an ultrafast synthesis of ultrahigh-molecular-weight polymers from various functional monomers prepared by single-electron-transfer living radical polymerization (SET-LRP) at ambient temperature and Cu was used to substitute the Cu to generate the radicals, which provides us a new strategy to generatemacroradicals in ourATNRCsystem. In this paper, the reaction conditions for SET are applied in the nitroxide radical coupling reaction and the macroradicals generated by SET mechanism at ambient temperature are trapped by nitroxide radicals, named as single-electron-transfer nitroxideradical-coupling (SET-NRC) reaction (Scheme 1). A living macroradical (Pn ) is generated from Pn-X (halogen-containing polymers) by SETmechanism by the oxidation of Cu toCu, which is efficiently trapped by TEMPO-Pm (TEMPO-containing polymers). Meanwhile, Cu is disproportionated into Cu and Cu to regenerate the Cu in polar solvent (methanol) in the presence of N ligands. However, in THF, no disproportionation of Cu was found (see Supporting Information). The coupling reactionswere conducted between bromine end polymers, such as polystyrene (PS), poly(tert-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), and TEMPO end polymers, poly(ethylene oxide) (PEO), poly(ecaprolectone) (PCL), in the presence of Cu/ N,N,N0,N00, N00-pentamethyldiethylenetriamine (PMDETA) under ambient temperature (25 ( 5 C). The TEMPO-containing PEO (TEMPO-PEO, Mn,NMR (molecular weight from H NMR): 3700 g/mol, Mn,GPC (molecular weight from GPC): 3500 g/mol, Mw/Mn: 1.08) was prepared by ring-opening polymerization (ROP) of EO in tetrahydrofuran (THF) using diphenylmethylpotassium (DPMK) and 4-hydroxyl2,2,6,6-tetramethylpiperidinyl-1-oxy (HTEMPO) as initiator. Polystyrene (PS-Br, Mn,NMR: 4100 g/mol; Mn,GPC: 4000 Mw/Mn: 1.07) precursor was prepared using the standard ATRP techniques (see Supporting Information). The coupling reaction was carried out as the followingprocedure:Anampule chargedwithTEMPOPEO (0.37 g, 0.1 mmol), Cu(0) (6.4 mg, 0.1 mmol), PMDETA (0.02 mL, 0.1 mmol), and THF (3 mL) was degassed by three freeze-pump-thaw cycles. Then PS-Br (0.41 g, 0.1 mmol) dissolved in THF (2 mL) was introduced into the ampule with additional three freeze-pump-thaw cycles. After 24 h magnetic stirring at ambient temperature, the ampulewas immersed in liquid nitrogen. Crude products were diluted with THF, and the solution was passed through neutral alumina to remove copper complex. THF was removed by evaporation, and the crude products were redissolved in CH3OH. The latter was passed through an ultrafiltration membrane to get rid of the impurities. The pure products were obtained by the concentration of reservedCH3OH solution to constant weight and dried at 35 C in vacuo. In SET, the C-X bond with low dissociation energy is cleaved by the formation of radical anion intermediates via an outersphere single-electron-transfer process, which does not show obvious dependency on the nature of the halide group. This means in our system C-Br bond dissociation occurred through the formation and decomposition of the radical anion intermediates. When PS-Br was mixed with TEMPO-PEO in the presence of Cu(0)/PMDETA at room temperature, the formed macroradicals (PS) were trapped by TEMPO groups immediately by the formation of alkoxyamines. In this process, the feed molar ratio of PS-Br and TEMPO-PEO was controlled at 1:1, and the presence of TEMPO-PEO groupmay increase the polarity of the solvent to benefit the coupling reaction. However, in the UV spectra of coupling product, only Cu at 262 nmwas detected; no Cu at 720 nm was found. It means that when THF was used as solvent in SET, no proportionation of Cu was conducted (see Supporting Information for details). After reaction, the remaining TEMPO-PEOand PS-Br residues were easily removed by membrane separation for TEMPO-PEO and extraction with cyclohexane for PS-Br (see Supporting Information for details) The gel permeation chromatography (GPC) traces of polystyrene with bromine end group (PS-Br), poly(ethylene oxide) with TEMPO end group (TEMPO-PEO), and PS-b-PEO are shown in Figure 1 with Gaussian distribution and low polydispersity (Mw/Mn< 1.10). A comparable experiment was carried out by introducing HTEMPO (0.017 g, 0.1 mmol) instead of TEMPO-PEO for the coupling reaction, in order to *To whom correspondence should be addressed. D ow nl oa de d by C A U L C O N SO R T IA A U ST R A L IA o n Ju ly 1 0, 2 00 9