49: , copolymers; click chemistry; nitroxide radical coupling; one-pot reaction; single electron transfer

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1 Copper(0)-Catalyzed One-Pot Synthesis of ABC Triblock Copolymers via the Combination of Single Electron Transfer Nitroxide Radical Coupling Reaction and Click Chemistry RONGKUAN JING, WENCHENG LIN, GUOWEI WANG, JUNLIAN HUANG The Key Laboratory of Molecular Engineering of Polymer, State Education Ministry of China, Department of Macromolecular Science, Fudan University, Shanghai , China Received 7 March 2011; accepted 24 March 2011 DOI: /pola Published online 25 April 2011 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: The synthesis of ABC triblock copolymers were accomplished by Cu(0)-catalyzed one-pot strategy combining single electron transfer-nitroxide radical coupling (SET-NRC) reaction with click chemistry. First, the precursors a,x-heterofunctionalized poly(ethylene oxide) (PEO) with a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) group and an alkyne group, polystyrene (PS), and poly(tert-butyl acrylate) (PtBA) with bromine or azide end group were designed and synthesized, respectively. Then, the one-pot coupling reactions between these precursors were carried out in the system of Cu(0)/Me 6 T- REN: The SET-NRC reaction between bromine group and nitroxide radical group, subsequently click coupling between azide and alkyne group. It was noticeable that Cu(I) generated from Cu(0) by SET mechanism was utilized to catalyze click chemistry. To estimate the effect of Cu(0) on the one-pot reaction, a comparative analysis was performed in presence of different Cu(0) species. The result showed that Cu(0) with more active surface area could accelerate the one-pot reaction significantly. VC 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: , 2011 KEYWORDS: atom transfer radical polymerization (ATRP); block copolymers; click chemistry; nitroxide radical coupling; one-pot reaction; single electron transfer INTRODUCTION With the tremendous advancements in polymerization techniques, 1 4 novel polymers with different compositions and chain architectures, such as linear, 5 star, 6 graft, 7 cyclic, 8 and hyperbranched, 9 have been successfully synthesized. Of the copolymers with complicated structures, ABC triblock copolymers 10 occupied an important position for their unique structure with three different blocks, which may lead to novel properties for potentially applications in many fields, such as self-assembly, crystallization, 13,14 and biomaterials. 15 One-pot strategy has been widely applied in the synthesis of different polymer architectures, because it can reduce purification steps and minimize the generation of chemical waste. Up to now, several ABC triblock copolymers have been prepared using a one-pot procedure However, those one-pot reactions required long reaction time (24 36 h). So, looking for a rapid and efficient one-pot strategy under mild conditions is still a significant work. In the past decades, Cu(I)-catalyzed azide-alkyne cycloaddition click chemistry 23 has been widely used in the preparation of complex architectures, due to its high specificity, quantitative yields, and near-perfect fidelity in the presence of most functional groups. In this type of click reaction, fresh Cu(I) plays an important role, which could improve the cycloaddition rate dramatically. 27 Recently, Cu(0)-catalyzed living radical polymerization by single electron transfer (SET- LRP) was developed by Percec Thus, a new reversible coupling strategy via the combination of single electron transfer (SET) 4,32 activation and nitroxide radical coupling (NRC) emerged as a new powerful tool for the synthesis of degradable and reversibly coupled macromolecules, 33 which was termed as single electron transfer-nitroxide radical coupling (SET-NRC) The new reaction relies on the formation of carbon-centered radicals by a single electron transfer reaction with Cu(0) and subsequently trapping by the nitroxide radical. 34 In the process, the Cu(I) was generated via the oxidation of Cu(0) by SET mechanism. 34 Therefore, it is possible to take the advantage of Cu(I) generated from Cu(0) in SET-NRC to catalyze the click reaction by a one-pot process. On the basis of the idea, a novel one-pot strategy combining SET-NRC reaction with click chemistry was suggested. In presence of Cu(0)/Me 6 TREN, the CAX bond is cleaved by the formation of radical anion intermediates via an outer sphere single electron transfer process, 32 the formed macroradicals were trapped by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) groups immediately with the formation of alkoxyamine. At the same time, Cu(I) generated in situ by SET Correspondence to: J. Huang ( jlhuang@fudan.edu.cn) Journal of Polymer Science Part A: Polymer Chemistry, Vol. 49, (2011) VC 2011 Wiley Periodicals, Inc WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

2 ARTICLE SCHEME 1 Mechanism of Cu(0)- catalyzed one-pot strategy combining SET-NRC with click chemistry. mechanism from Cu(0) was used directly to catalyze the click coupling between azide group and alkyne group (Scheme 1). In this article, we utilized the one-pot strategy combining SET-NRC reaction with click chemistry to prepare a series of ABC triblock copolymers. The effect of Cu(0) species on this one-pot reaction was investigated in details. RESULTS AND DISCUSSION Synthesis and Characterization of Precursors All of the precursors were prepared by living polymerization and then modification of end groups. First, a-tempo-xhydroxyl-poly(ethylene oxide) (TEMPO-PEO-OH) was prepared by anionic ring-opening polymerization of ethylene oxide (EO) in THF using diphenylmethyl potassium (DPMK) and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl (HTEMPO) as initiators according to literature, 21 the molecular weight of TEMPO-PEO-OH was 7300 g/mol by size exclusion chromatography (SEC) with linear PEO for calibration (Fig. 1). The 1 H NMR signal at ppm assigned to methyl of TEMPO group showed the successful synthesis of TEMPO- PEO-OH. Subsequently, the propargyl group was introduced to TEMPO-PEO-OH by nucleophilic substitution reaction between active hydroxyl group and propargyl bromide at 0 C. In 1 H NMR spectrum [Fig. 2(C)], two new peaks (h, i) at 4.20 and 2.44 ppm assigned to alkyne group were observed after the hydroxyl group was converted to alkyne group, which was an indicative of the formation of a-tempo-xalkyne-poly(ethylene oxide) (TEMPO-PEO-Alkyne). The precursors x-bromine-polystyrene (PS-Br) and x-bromine-poly(tert-butyl acrylate) (PtBA-Br) were synthesized by typical atom transfer radical polymerization (ATRP). The reactions were stopped at low conversion (under 30%) to ensure a high degree of bromine chain-end functionality. 39 Molecular weights of PS-Br and PtBA-Br were 2,500 and 2,000 g/mol (Fig. 1), respectively, measured by SEC with linear PS for calibration. In 1 H NMR spectra, the existence of bromine atom in PS-Br was confirmed by the appearance of resonance signal at ppm assigned to methine proton (e) in CH(Ph)ABr [Fig. 2(B)]; and the existence of bromine atom in PtBA-Br was supported by the appearance of the resonance signal at ppm assigned to methine proton (c) in ACH 2 CHABr [Fig. 3(A)]. The bromine atoms at the end of the polymers were converted quantitatively into azide groups by reaction with sodium azide in DMF at room temperature. Thus, x-azide-polystyrene (PS-N 3 )andx-azide-poly(tert-butyl acrylate) (PtBA- N 3 ) were obtained by nucleophilic substitution reaction. Based on 1 H NMR analysis, the azidation of PS was confirmed by the disappearance of resonance signal at ppm assigned to methine proton in ACH(Ph)ABr and appearance of a new resonance signal at 3.95 ppm assigned to methine proton (e) in ACHA(Ph)AN 3 group of PS-N 3 [Fig 3(B)]. The observation of a new resonance signal at ppm assigned to methine proton (c) in ACH 2 CHAN 3 group of PtBA-N 3 showed the azidation of PtBA was complete [Fig. 2(A)]. Cu(0) Catalyzed One-Pot Synthesis of ABC Triblock Copolymers ABC triblock copolymer PS-b-PEO-b-PtBA was synthesized by one-pot strategy using precursors PS-Br, PtBA-N 3 and TEMPO-PEO-Alkyne (Scheme 2). In the presence of Cu(0)/ Me 6 TREN, SET-NRC reaction between bromine group and TEMPO group proceeded, meanwhile, Cu(I) was generated by SET mechanism. Then, the polymer with azide end group was added into the polymerization mixture, followed by a click coupling between azide group and alkyne group in presence of Cu(I). In the one-pot process, the feeding PS-Br and PtBA-N 3 were slightly excessive comparing with TEMPO-PEO-Alkyne, the molar ratio was about 1.3/1.3/1. After reaction, the excessive PS and PtBA can be easily removed from the mixture by extraction with cyclohexane/petroleum ether mixture (v/v: 1/1). In Figure 1, the SEC trace of triblock copolymer PS-b- FIGURE 1 SEC curves of ABC triblock copolymer PS-b-PEO-b- PtBA and its precursors: PtBA-Br, PS-Br, and TEMPO-PEO-OH. SYNTHESIS OF ABC TRIBLOCK COPOLYMERS, JING ET AL. 2595

3 JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI /POLA FIGURE 2 1 H NMR spectra of (A) PtBA-N 3, (B) PS-Br, (C) TEMPO- PEO-Alkyne, and (D) PS-b-PEO-b- PtBA (solvent: CDCl 3 ). PEO-b-PtBA was smooth, and no tail was observed in the molecular weight region of the precursors, which meant that excess PS and PtBA precursors were removed thoroughly. The one-pot process was supported by 1 H NMR spectra. Figure 2 showed the 1 H NMR of triblock copolymer PS-b-PEO-b- PtBA and its precursors. The resonance signal at 2.22 ppm assigned to methine protons (b) of PtBA, the signal at ppm assigned to phenyl protons (f) of PS, and the signal at ppm assigned to the methylene protons (g) of PEO were detected, respectively [Fig. 2(D)]. These results indicated the formation of PS-b-PEO-b-PtBA, which meant the one-pot reaction combining SET-NRC with click chemistry was successful. The actual molecular weight (M n,act ) of triblock copolymer was determined by the integral area of PEO block at (methylene protons, repeating unit of PEO) against that of PS block at (phenyl protons, repeating unit of PS) and that of PtBA block at 2.22 ppm (methine protons, repeating unit of PtBA) as formula 1 showed: and 44 were the molecular weights of monomers St, tba, and EO, respectively. The formation efficiency (EF Formation ) of triblock copolymers could be obtained from the ratio of actual molecular weight to theoretical molecular weight, using formula 2. EF Formation ¼ M n;act M n;theo 100% (2) M n;act ¼ 4A f M PEO 5A g þ 4A b M PEO A g þM PEO (1) Here as Figure 2(D) showed, A b represented the integral area sum of the methine protons (b) on PtBA block, A f represented the integral area sum of the phenyl protons (f) on PS block, and A g represented the integral area sum of the methylene protons (g) on PEO block; M PEO represented the molecular weight of TEMPO-PEO-Alkyne; the values 104, 128, FIGURE 3 1 H NMR spectra of (A) PtBA-Br, (B) PS-N 3, and (C) PtBA-b-PEO-b-PS (solvent: CDCl 3 ) WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

4 ARTICLE SCHEME 2 One-pot synthesis of ABC triblock copolymer PS-b- PEO-b-PtBA via the combination of SET-NRC and click chemistry. Here, theoretical molecular weight (M n,theo ) was the sum of the separate molecular weight of precursors PS, PtBA and PEO. By using precursors PtBA-Br, PS-N 3 and TEMPO-PEO-Alkyne, another triblock copolymer PtBA-b-PEO-b-PS was also prepared by the one-pot technique, which were supported by SEC and 1 H NMR. The SEC trace of PtBA-b-PEO-b-PS was a monomodal peak with a narrow polydispersity index (PDI) of 1.08 (Table 1, entry C), which meant the excess precursors were removed thoroughly. Figure 3 showed the 1 H NMR of triblock copolymer PtBA-b-PEO-b-PS and its precursors PtBA-Br and PS-N 3. The resonance signal at 2.22 ppm assigned to methine protons (b) of PtBA, the signal at ppm assigned to phenyl protons (f) of PS, and the signal at ppm assigned to methylene protons (g) of PEO were detected, respectively. These results showed the successful preparation of PtBA-b-PEO-b-PS using precursor with different group connected to bromine atom (PtBA-Br). Effect of Cu(0) Species on the One-Pot Reaction of SET-NRC and Click Chemistry To estimate effect of Cu(0) species on the one-pot reaction, two kinds of Cu(0) were used: One was nanosized Cu(0) powder, the other was nascent Cu(0), which was generated in situ via the reduction of Cu(II) in the presence of Zn(0). Comparing entry A with B in Table 1, the formation efficiency of triblock copolymer PS-b-PEO-b-PtBA in presence of nascent Cu(0) was higher than that in the presence of nanosized Cu(0) powder. It is well known that the active surface area of Cu(0) was responsible for the activation of polymer chain with bromine group in single electron transfer process. 30,31,40 Increasing the active surface area of Cu(0) could accelerate the generation of radicals in SET-LRP, 32 and the generation of macroradical was a rate-determining step in SET-NRC reaction. 35 When the nascent Cu(0) with more active surface area was introduced into the one-pot reaction, more macroradicals would be produced by SET mechanism, and the SET-NRC reaction would be carried out quickly. Meanwhile, more fresh Cu(I) would be generated, which could accelerate the click reaction too. 27 However, when nanosized Cu(0) powder was used, this active area was less than that of nascent Cu(0) because of surface oxidization. Therefore, when a high-activating nascent Cu(0) was used as the catalyst, the one-pot reaction combining SET-NRC with click chemistry would be accelerated. Accordingly, the TABLE 1 The Data for One-Pot Synthesis of ABC Triblock Copolymers Triblock Copolymers Entry Cu(0) c P m -X d P m -N 3 e M n,sec f (g/mol) PDI f M n,act g (g/mol) M n,theo h (g/mol) EF Formation i (%) A a Cu(0) powder PS-Br PtBA-N 3 15, ,300 11, B a Nascent Cu(0) PS-Br PtBA-N 3 14, ,600 11, C b Nascent Cu(0) PtBA-Br PS-N 3 14, ,200 11, a PS-b-PEO-b-PtBA, its precursors were composed of PS-Br, TEMPO- PEO-Alkyne, PtBA-N 3. b PtBA-b-PEO-b-PS, its precursors were composed of PtBA-Br, TEMPO- PEO-Alkyne, PS-N 3. c The type of Cu(0) used in the one-pot reaction, Cu(0) powder was nanosized, nascent Cu(0) was produced via reduction of CuBr 2 in presence of Zn(0). [CuBr 2 ]:[Zn] ¼ 1:1. d Bromine-containing precursor. e Azide-containing precursor. f Measured by SEC in THF with linear PS as standard. g Actual molecular weight, measured by formula 1. h Theory molecular weight, the sum of the separate molecular weight of precursors PS, PtBA, and PEO. i The formation efficiency of triblock copolymers, measured by formula 2. SYNTHESIS OF ABC TRIBLOCK COPOLYMERS, JING ET AL. 2597

5 JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI /POLA formation efficiency of triblock copolymer became higher, which proved the postulation that the active surface area of Cu(0) had a great effect on coupling rate of the one-pot reaction combining SET-NRC reaction with click chemistry. All the data of ABC triblock copolymers were summarized in Table 1. It was found the formation efficiencies of ABC triblock copolymers were all high in the presence of nascent Cu(0) (Table 1, entries B and C), which showed the one-pot technique combining SET-NRC with click chemistry was effective and reliable. EXPERIMENTAL Materials Ethylene oxide (EO; Sinopharm Chemical Reagent, SCR) was dried by CaH 2 for 48 h and distilled under N 2 before use. Styrene (St; 99.5%) purchased from SCR was washed with a 15% NaOH aqueous solution and water successively, dried over anhydrous MgSO 4, further dried over CaH 2, and then distilled under reduced pressure twice before use. tert-butyl acrylate (tba; 99%; SCR), propargyl bromide (99%), N,Ndimethylformamide (DMF, 99%), and dimethyl sulfoxide(dmso; 98%) were dried over CaH 2 and distilled under reduced pressure before use. Copper powder (Cu(0), <100 nm, 99.8%, Aldrich), zinc powder (Zn(0), <150 lm, % Aldrich), cuprous bromide (CuBr, 99%, Aldrich), cupric bromide (CuBr 2, 99%, Aldrich), N,N,N 0,N 00,N 00 -pentamethyldiethylenetriamine (PMDETA, Aldrich), and ethyl 2-bromoisobutyrate (EBiB, Aldrich) were used as received, and other reagents were all purchased from SCR and purified by standard methods. 4-Hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl (HTEMPO) was prepared according to a previous work 41 and purified by recrystallized with hexane as the solvent. Tris(2-(dimethylamino)ethyl)amine (Me 6 TREN) was synthesized as described in the literature 42. Diphenylmethyl potassium (DPMK) solution was freshly prepared according to the literature, 43 the concentration was 0.75 mol/l. Preparation of TEMPO-PEO-Alkyne First, TEMPO-PEO-OH was prepared using the following procedure: HTEMPO (0.35 g, 2.0 mmol), dried by azeotropic distillation with toluene, was dissolved in 80 ml THF. The mixture was introduced into a 250-mL ampule, and then DPMK (1.33 ml, 1.0 mmol) and EO (17.0 ml, 336 mmol) were injected into the ampule under nitrogen successively. The ampule reacted at 60 C for 72 h. At the end of the polymerization, excessive methanol was added to terminate the reaction. After removing the solvent, the mixture was diluted with methylene chloride (CH 2 Cl 2 ) and precipitated into an excessive amount of diethyl ether for three times. The precipitate was dried under vacuum at 40 C for 12 h, and the pink powder was obtained. 1 H NMR (CD 3 OD, in the presence of calculated amounts of HCOONH 4 and Pd/C) d (ppm): (m, ACH 3 ), 1.41 and 1.95 (m, ACH 2 A), (m, 4H, ACH 2 CH 2 OA). SEC: M n, 7300 g/mol, PDI: Then, to a 250-mL dried ampule, TEMPO-PEO-OH (M n,sec : 7300 g/mol, 8 g, 1.1 mmol) and THF (60 ml) were added. The system was bubbled with N 2, and DPMK solution was introduced until the solution was turned into reddish-brown. After the ampule was placed in ice bath, propargyl bromide (1.96 ml, 2.62 g, 22 mmol) was added dropwise during 2 h, and the reaction was continued for 24 h at room temperature. TEMPO-PEO-Alkyne was obtained by separation of the formed salts and precipitation in diethyl ether twice, and dried under vacuum at 40 Cfor12h. 1 H NMR (CDCl 3 ) d (ppm): (m, ACH 3, ACH 2 A), 2.44 (t, 1H, AOCH 2 CBCH), (m, 4H, ACH 2 CH 2 OA), 4.20 (d, 2H, AOCH 2 CBCH). Synthesis of PS-Br and PS-N 3 The precursor PS-Br was synthesized by ATRP using EBiB as initiator and CuBr/PMDETA as catalyst. The typical preparation procedure for PS-Br: EBiB (0.32 ml, 2.16 mmol), CuBr (0.31 g, 2.16 mmol), PMDETA (0.45 ml, 2.16 mmol), and St (20 ml, 175 mmol) were dissolved in 10 ml toluene. The mixture was added to a 50-mL Schlenk flask and degassed by three freeze-pump-thaw cycles. The ampule was immersed in oil bath at 90 C for 2 h. The reaction was stopped via dipped in liquid nitrogen. The products were diluted with THF, passed through a column chromatograph filled with neutral alumina to remove the copper complex, and precipitated in cold methanol twice. The precipitate of PS-Br was collected and dried in vacuum at 40 C for 12 h. 1 H NMR(CDCl 3 ), d (ppm): (m, 9H, AC(CH 3 ) 2 -PS, CH 3 CH 2 OA), (m, 3H, ACH 2 CHA), (m, 2H, CH 3 CH 2 OA), (m, 1H, ACH(Ph)ABr), (m, 5H, AC 6 H 5 ); Conversion:29%. SEC, M n : 2500 g/mol, PDI: The typical preparation procedure for PS-N 3 : PS-Br (M n,sec : 2500 g/mol, 1.0 g, 0.4 mmol) was dissolved in 10-mL DMF, sodium azide (0.26 g, 4 mmol) was added to the solution. The mixture was stirred at room temperature over night. After precipitation into methanol/water mixture (v/v: 1/1), PS-N 3 was collected and dried in vacuum at 40 C for 4 h. 1 H NMR(CDCl 3 ), d (ppm): (m, 9H, AC(CH 3 ) 2 -PS, CH 3 CH 2 OA), (m, 3H, ACH 2 CHA), (m, 2H, CH 3 CH 2 OA), 3.95 (m, 1H, ACH(Ph)AN 3 ), (m, 5H, AC 6 H 5 of PS). Synthesis of PtBA-Br and PtBA-N 3 PtBA-Br was prepared by ATRP of tba in acetone using EBiB as initiator and CuBr/PMDETA as catalyst system. The preparation procedure: To a 100-mL ampule, EBiB (0.32 ml, 2.16 mmol), CuBr (0.215 g, 1.5 mmol), PMDETA (0.314 ml, 1.5 mmol), and tba (26 ml, 179 mmol) in acetone (26 ml) were charged, and then the mixture was vacuumed by three freeze-pump-thaw cycles and left under nitrogen. The ampule was immersed in oil bath at 60 C for 2.5 h and stopped by dipping the ampule into liquid nitrogen. The reaction mixture was diluted with THF and filtered through an activated neutral alumina column to remove the copper 2598 WILEYONLINELIBRARY.COM/JOURNAL/JPOLA

6 ARTICLE salts. The polymer precipitated in CH 3 OH/H 2 O (v/v ¼ 1/1) was collected and dried at 40 C in vacuum for 12 h. 1 H NMR (CDCl 3 ), d (ppm): (m, 6H, AC(CH 3 ) 2 ), (m, 3H, CH 3 CH 2 OA), (m, 11H, ACH 2 CHA and ACOOC(CH 3 ) 3 ), 2.22 (m, 1H, ACH 2 CHA), (m, 3H, CH 3 CH 2 OA and ACHABr). Conversion: 18.5%. SEC, M n : 2000 g/mol, PDI: The typical preparation procedure for PtBA-N 3 : PtBA-Br (M n,sec : 2000 g/mol, 0.8 g, 0.4 mmol) was dissolved in 8 ml DMF, and sodium azide (0.26 g, 4 mmol) was added to the solution. The mixture was stirred at room temperature over night. Then, 20 ml CH 2 Cl 2 was added into the mixture and washed three times with deion water. The organic layer was dried with anhydrous MgSO 4, and the solvent was removed by vacuum. The product PtBA-N 3 was collected and dried at 40 C in vacuum for 4 h. 1 H NMR (CDCl 3 ) d (ppm): (m, AC(CH 3 ) 2 ), (m, CH 3 CH 2 OA), (m, 11H, ACH 2 CHA and ACOOC(CH 3 ) 3 ), 2.22 (m, 1H, ACH 2 CHA), (m, ACHAN 3 ), 4.12 (m, CH 3 CH 2 OA). Cu(0)-Catalyzed One-Pot Synthesis of Triblock Copolymers Typically, Cu(0)-catalyzed one-pot synthesis of PS-b-PEO-b- PtBA using precursors PS-Br, PtBA-N 3, and TEMPO-PEO- Alkyne was carried out as the following procedure: First, into a Schlenk flask, PS-Br (M n,sec : 2500 g/mol, 89 mg, mmol), TEMPO-PEO-Alkyne (M n,sec : 7300 g/mol, 200 mg, mmol), Me 6 TREN (18.9 mg, mmol), and the mixture of THF and DMSO (1/1 by volume, 3.7 ml) were added. Oxygen was removed from the system by three freeze-pump-thaw cycles. Nanosized Cu(0) powder (5.2 mg, mmol) was quickly added to the frozen solution, and the flask was re-evacuated, backfilled with N 2, and sealed. The reaction mixture was stirred at 50 C for 1 h. After then, the degassed solution of PtBA-N 3 (M n,sec : 2000 g/mol, 71.2 mg, mmol), and the mixture of THF and DMSO (1/1 by volume, 1.8 ml) was added into the Schlenk flask via the side arm. The reaction mixture was stirred at 50 C for another 1 h and then immersed in liquid nitrogen. After centrifugation, the product was diluted with methylene chloride and washed three times with distilled water. The organic layer was dried with anhydrous MgSO 4. After removal of solvents under reduced pressure, the crude product was extracted with cyclohexane/petroleum ether mixture (1/1 by volume) to remove unreacted PS and PtBA. After centrifugation, the white product was collected and dried under vacuum at 40 C. 1 H NMR (CDCl 3 ) d (ppm): (m, 21H, ACH 3 of TEMPO group, AC(CH 3 ) 2 -PS, AC(CH 3 ) 2 -PtBA, and CH 3 CH 2 OA introduced by EBiB), (m, 14H, ACH 2 CHA of PS, ACH 2 CHA and AC(CH 3 ) 3 of PtBA), 2.22 (s, 1H, ACH 2 CHA of PtBA), (m, 4H, ACH 2 CH 2 OA of PEO), (m, CH 3 CH 2 OA, end group of PtBA), (m, 5H, AC 6 H 5 of PS), (ACHA of triazole ring). SEC, M n : 15,500 g/ mol, PDI: Another triblock copolymer PS-b-PEO-b-PtBA was prepared by the one-pot method in the presence of nascent Cu(0), which was generated in situ via the reduction of CuBr 2 (18.4 mg, mmol) in the presence of Zn(0) (5.4 mg, mmol). (SEC, M n : 14,200 g/mol, PDI: 1.05). Similarly, PtBA-b- PEO-b-PS was also prepared in presence of nascent Cu(0) by the one-pot technique using different precursors PtBA-Br, PS-N 3 and TEMPO-PEO-Alkyne. (SEC, M n : 14,300 g/mol, PDI: 1.08). Measurements Size exclusion chromatography was performed on an Agilent 1100 with a G1310A pump, a G1362A refractive-index detector, and a G1314A variable-wavelength detector with THF as the eluent at a flow rate of 1.0 ml/min at 35 C. One 5-lm LP gel column (500 E, molecular range g/mol) and two 5-lm LP gel mixed bed column (molecular range g/mol) were calibrated by polystyrene standards. For PEO, SEC was performed in 0.1 M aqueous NaNO 3 at 40 C with an elution rate of 0.5 ml/min with the same instruments, except that the G1314A variable-wavelength detector was substituted by a G1315A diode-array detector, and PEO standards were used for calibration. 1 H NMR spectra were obtained at a DMX500 MHz spectrometer with tetramethylsilane (TMS) as the internal standard. CONCLUSIONS In summary, a new strategy for one-pot synthesis of ABC triblock copolymers via the combination of click chemistry with SET-NRC reaction was presented, in which the Cu(I) generated from Cu(0) by SET mechanism was utilized smartly to catalyze click reaction. The high-activating nascent Cu(0) generated in situ via the reduction of Cu(II) would accelerate the one-pot reaction and improve the formation efficiencies of triblock copolymers. The authors appreciate the financial support to this research by the Natural Science Foundation of China (No ) and Natural Science Foundation of Shanghai (No. 08ZR ). REFERENCES AND NOTES 1 Hawker, C. J. J Am Chem Soc 1994, 116, Wang, J. S.; Matyjaszewski, K. J Am Chem Soc 1995, 117, Chiefari, J.; Chong, Y. K.; Ercole, F.; Krstina, J.; Jeffery, J.; Le, T. P. T.; Mayadunne, R. T. A.; Meijs, G. F.; Moad, C. L.; Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1998, 31, Percec, V.; Guliashvili, T.; Ladislaw, J. 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