Ambient Temperature “Flash” SARA ATRP of Methyl Acrylate in Water

Article pubs.acs.org/Macromolecules

Ambient Temperature “Flash” SARA ATRP of Methyl Acrylate in Water/Ionic Liquid/Glycol Mixtures Joaõ R. C. Costa,† Patrícia V. Mendonça,† Pedro Maximiano,† Arménio C. Serra,† Tamaz Guliashvili,*,§ and Jorge F. J. Coelho*,† †

CEMUC, Department of Chemical Engineering, University of Coimbra, 3030-790 Coimbra, Portugal Cytosorbents Inc., 7 Deer Park Drive, Monmouth Junction, New Jersey 08852-192, United States

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S Supporting Information *

ABSTRACT: The supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) of methyl acrylate (MA) in DMSO/ BMIM-PF6/glycol mixtures (DMSO, dimethyl sulfoxide; BMIM-PF6, 1-butyl3-methylimidazolium hexafluorophosphate) near room temperature (30 °C), using different SARA agents, is reported. The unusual “hyperpolarity” effect within the solvent mixture allowed very fast and controlled polymerizations (Đ < 1.1) during the entire reaction time. Remarkably, the replacement of DMSO by water in the reaction mixture led to a “flash” polymerization with monomer conversion reaching 92% in only 11 min (degree of polymerization, 222), yet still affording good control over the polymerization.

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INTRODUCTION Reversible deactivation radical polymerization (RDRP) techniques are valuable tools for macromolecular engineering, because they allow the synthesis of tailor-made polymers with targeted molecular weight, composition, architecture, topology and low dispersity (Đ).1 Atom transfer radical polymerization (ATRP)2 is one of the most versatile and robust RDRP techniques, which has been successfully applied to the polymerization of a vast range of monomer families, such as (meth)acrylates,3−5 (meth)acrylamides,6,7 4-vinylpyridine,8,9 styrene,10−12 and vinyl chloride.13,14 The major disadvantage associated with ATRP is attributed to the use of a high concentration of metal catalyst to mediate the polymerization.2 New ATRP variation techniques, namely, activators regenerated by electron transfer (ARGET) ATRP,15 supplemental activator and reducing agents (SARA) ATRP,4,16 initiators for continuous activator regeneration (ICAR) ATRP,17 and electrochemically mediated ATRP (e-ATRP),18 have been developed affording the use of a very low concentration of metal catalyst. Recently, a metal-free ATRP process was also developed.19,20 All these contributions aimed to extend the range of application of ATRP by creating ecofriendly processes as much as possible. SARA ATRP has been studied during the past 4 years, and it has proved to be a very attractive technique from the environmental standpoint because the polymerizations can be carried out with zerovalent metals4,10,16 or even with FDAapproved inorganic sulfites21−24 as the SARA agents. An important step toward industrialization of this technology has been achieved recently with use of sulfolane as a “universal” solvent for the SARA ATRP of acrylates, methacrylates, styrene, and vinyl chloride.13 In addition, the use of water or ecofriendly alcohol/water mixtures as the polymerization solvent has been successfully implemented.6,25 Recently, our research group has © XXXX American Chemical Society

reported the use of an ionic liquid (BMIM-PF6: 1-butyl-3methylimidazolium hexafluorophosphate), in combination with dimethyl sulfoxide (DMSO), as the solvent mixture for the SARA ATRP of methyl acrylate (MA) at room temperature.26 An unusual synergistic effect of the BMIM-PF6/DMSO mixture was found, which resulted in very fast polymerizations, while the Đ remained always below 1.05. It is known that BMIM-PF6 can also exhibit synergistic effects with other solvents, particularly an unusual “hyperpolarity” effect with glycols.27,28 In this work, the influence of the presence of glycols in the BMIM-PF6/DMSO mixtures for the SARA ATRP of MA at room temperature was investigated. To the best of our knowledge, this is the first time that ionic liquids/glycols are used as solvents in ATRP. The hyperpolarity effect within the BMIM-PF 6/DMSO/glycol mixture led to ultrafast and controlled polymerizations.

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EXPERIMENTAL SECTION

Materials. BMIM-PF6 (> 98%; TCI (Tokyo Chemical Industry Co. LTD)), copper(II) bromide (CuBr2, +99% extra pure, anhydrous; Acros), deuterated chloroform (CDCl3, +1% tetramethylsilane (TMS); Euriso-top), DMSO (+99.8% extra pure; Acros), diethylene glycol (DEG, 99%; Sigma-Aldrich), ethyl 2-bromoisobutyrate (EBiB, 98%; Aldrich), ethylene glycol (EG, ≥99%; Sigma-Aldrich), iron powder (Fe(0), 99%, ∼70 mesh; Acros), polystyrene (PS) standards (Polymer Laboratories), Reichardt’s dye (30) (90; Sigma-Aldrich), sodium hydrosulfite also known as sodium dithionite (Na2S2O4, 85%, technical grade; Aldrich), and triethylene glycol (TEG, 99%; Acros) were used as received. MA (99% stabilized; Acros) was passed over a sand/alumina column before use to remove the radical inhibitor. Received: August 12, 2015 Revised: September 22, 2015

A

DOI: 10.1021/acs.macromol.5b01795 Macromolecules XXXX, XXX, XXX−XXX

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Macromolecules Metallic copper (Cu(0) wire, d = 1 mm, Sigma-Aldrich) was washed with HCl in methanol and subsequently rinsed with methanol and dried under a stream of nitrogen following the literature procedures.29 Me6TREN was synthesized according the procedure described in the literature.30 Purified water (Milli-Q, Millipore, resistivity >18 MΩ·cm) was obtained by reverse osmosis. Tetrahydrofuran (THF, high-performance liquid chromatography (HPLC) grade; Panreac) was filtered (0.2 μm filter) under reduced pressure before use. Techniques. The chromatographic parameters of the samples were determined using high performance size-exclusion chromatography (HPSEC), Viscotek (Viscotek TDAmax) with a differential viscometer (DV), right-angle laser-light scattering (RALLS) (Viscotek), low-angle laser-light scattering (LALLS) (Viscotek), and refractive index (RI) detectors. The column set consisted of a Tguard column (8 μm) followed by one Viscotek T2000 column (6 μm), one MIXED-E PLgel column (3 μm), and one MIXED-C PLgel column (5 μm). A HPLC dual piston pump was set at a flow rate of 1 mL/min. The eluent, THF, was previously filtered through a 0.2 μm filter. The system was also equipped with an online degasser. The tests were done at 30 °C using an Elder CH-150 heater. Before the injection (100 μL), the samples were filtered through a polytetrafluoroethylene (PTFE) membrane with 0.2 μm pore. The system was calibrated with narrow polystyrene (PS) standards. The dn/dc of PMA was determined as 0.063. The number-average molecular weight (MnSEC) and dispersity (Đ) of the synthesized polymers were determined by multidetector calibration using OmniSEC software, version 4.6.1.354. The 400 MHz 1H NMR spectra of the reaction mixture samples were recorded on a Bruker Avance III 400 MHz spectrometer, with a 5 mm TIX triple-resonance detection probe, in CDCl3 with TMS as an internal standard. The monomer conversion was determined by integration of monomer and polymer peaks using MestRenova software, version 6.0.2-5475. The UV−vis studies were performed with a Jasco V-530 spectrophotometer. The analyses were carried out in the 350−1100 nm range at room temperature. UV−Vis Spectroscopy of BMIM-PF6/DMSO/Glycol and BMIM-PF6/H2O/TEG. Typically, the Reichardt’s dye (30) (1 mg, 50 μM) was weighed in a vial, followed by BMIM-PF6 and subjected to vigorous stirring until the complete dissolution of the dye. Then, a glycol/DMSO (or TEG/water) mixture was added to the vial, and the resulting mixture was stirred leading to a homogeneous solution. From these solutions, samples with different molar fractions of glycols were prepared with a final volume of 3 mL. Each sample solution was then added to a quartz UV−vis cuvette and placed in the spectrophotometer for spectra acquisition. The absorbance was measured in the 350−1100 nm range at room temperature. Determination of ET(30) in BMIM-PF6/DMSO/Gycols and BMIM-PF6/H2O/TEG Mixtures. The solvent medium polarity was evaluated by the ET(30) parameter, through the solvatochromic visible adsorption of the betaine dye no. 30 (Reichardt’s dye (30)). This parameter is defined as the molar transition energies, commonly in kilocalories per mole, of the Reichardt’s dye (30) measured in solvents with different polarities at room temperature (25 °C) and normal pressure (1 bar), according to the expression ET(30) = 28591.5/λmax (λ in nanometers),31 where λmax is the wavelength of the maximum absorption band of the Reichardt’s dye (30). Procedures. Typical Procedure for the [Na2S2O4]0/[CuBr2]0/ [Me6TREN]0 = 1/0.1/0.2 Catalyzed SARA ATRP of MA (DP = 222) in BMIM-PF6/DMSO/TEG = 45/45/10 (v/v). In a typical SARA ATRP polymerization of MA, Na2S2O4 (40.98 mg, 0.20 mmol) was placed in a Schlenk reactor. A mixture of CuBr2 (4.47 mg, 0.02 mmol), Me6TREN (9.22 mg, 0.04 mmol), DMSO (0.90 mL), TEG (0.20 mL), and BMIM-PF6 (0.90 mL) was added to the reactor. Finally, a mixture of MA (4 mL, 44.42 mmol) and EBiB (39.82 mg, 0.20 mmol) was also added to the Schlenk reactor, which was sealed and frozen in liquid nitrogen. The Schlenk reactor containing the reaction mixture was deoxygenated with four freeze−vacuum−thaw cycles and purged with nitrogen. The reactor was placed in a water bath at 30 °C with stirring

(700 rpm). During the polymerization, different reaction mixture samples were collected by using an airtight syringe and purging the side arm of the Schlenk reactor with nitrogen. The samples were analyzed by 1H NMR spectroscopy, to determine the monomer conversion, and by SEC, to determine the MnSEC and Đ of the polymers. Typical “One-Pot” Chain Extension of PMA-Br. MA (1.0 mL, 11.0 mmol), EBiB (54.9 mg, 0.28 mmol), CuBr2 (6.2 mg, 27.6 μmol), Me6TREN (12.7 mg, 55.2 μmol), water (50 μL), BMIM-PF6 (230 μL), and TEG (230 μL) were added to a 25 mL Schlenk flask equipped with a magnetic stirrer bar. Next, Na2S2O4 (56.5 mg, 0.28 mmol) was added to the Schlenk flask, which was sealed with a glass stopper, deoxygenated with four freeze−vacuum−thaw cycles, and purged with nitrogen. The reaction was allowed to proceed with stirring (700 rpm) at 30 °C. When the monomer conversion reached more than 95%, a degassed mixture of MA (11.9 mL, 0.14 mol), water (440 μL), BMIM-PF6 (2.0 mL), and TEG (2.0 mL) was added to the Schlenk flask under nitrogen. The monomer conversion was determined by 1H NMR spectroscopy and the MnSEC and Đ were determined by SEC.

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RESULTS AND DISCUSSION Influence of the Glycol Structure in the Polymerization Kinetics. In a previous work by our research group,26 an unusual synergistic solvent effect within DMSO/BMIM-PF6 mixtures was found, as the solvent for the Na2S2O4/CuBr2/ Me6TREN-catalyzed SARA ATRP of MA. This synergistic effect induced very fast polymerizations, in comparison to the use of pure DMSO as the reaction solvent, while maintaining an excellent control over the molecular weight (Đ < 1.05) of the polymers. Interestingly, it is also known that BMIM-PF6 can exhibit a particular hyperpolarity effect in the presence of glycols.27 In this work, the hyperpolarity effect within DMSO/ BMIM-PF6/glycols mixtures was evaluated in the SARA ATRP of MA. Three different glycols were investigated (TEG, DEG, and EG) to evaluate the influence of different chain lengths and the number of ether and hydroxyl groups (Figure 1) on this

Figure 1. Chemical structure of the different glycols investigated.

hyperpolarity effect and on the polymerization kinetics. For instance, it is proposed in the literature28 that both chemical groups are responsible for the tuning of the physicochemical properties of BMIM-PF6/PEG mixtures (e.g., hydrophilicity), in comparison to pure mixture components (hyperpolarity effect), due to hydrogen bonding.32 The investigation started with the evaluation of the polarity of the solvent mixtures using the electronic transition energy parameter ET(30), which is the most commonly used scale to measure the polarity of solvents.32 As previously reported,26 this prediction was obtained by measuring the absorbance of BMIM-PF6/DMSO/glycol ternary mixtures in the presence of the solvatochromic probe Reichardt’s dye (30). The results from Figure 2 suggest that the BMIM-PF6/DMSO/glycol mixtures exhibit a synergistic effect for all the molar percentages of glycols, as judged by the higher ET(30) values when compared with the expected ones (dashed line). Additionally, it was possible to observe a hyperpolarity effect for all glycols investigated, as confirmed by the ET(30) values being higher than the ones obtained for solutions with 0% and 100% of glycol. It was reported that the presence of ionic liquids induces an increase in the polymerization rate of MA because of both a B

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ization) (Figure 3b). These results clearly demonstrate that the polarity of the solvent mixture has a direct influence on the polymerization process. However, it seems that this is not the only parameter influencing the polymerization rate, because the three glycols present similar ET(30) values (see Figure 2 for 8% molar fraction) but yet led to polymerizations with different rates, particularly when DEG was used in the solvent mixture (Figure 3a). Other factors such as the change in the catalyst solubility, catalyst activity (namely kred and KATRP constants), interaction with monomer, or even the possible complexation of glycols with sodium Na+ (derived from Na2S2O4 catalyst)36 might have also contributed to the differences observed. Influence of the SARA Agent Nature. In addition to the synergetic effect studied for the above-mentioned SARA agent (Na2S2O4), the use of other cocatalysts (Fe(0) and Cu(0)) was investigated using the DMSO/BMIM-PF6/TEG mixture, once it provided the fastest polymerization. The experiments with both SARA agents (Figure 4a) displayed a similar effect in the

Figure 2. Experimental ET(30) values as a function of the glycol molar fraction in BMIM-PF6/DMSO/glycol mixtures. Glycols: TEG (red symbols), EG (black symbols), and DEG (green symbols).

decrease in the rate constant of termination (kt) and an increase in the rate constant of propagation (kp).33−35 The increase in the polarity of the medium, due to the presence of the ionic liquid BMIM-PF6, leads to a decrease of the propagation activation energy, allowing a higher contribution of chargetransfer structures (interaction of singly occupied molecular orbital of the propagating macroradical with lowest unoccupied molecular orbital of the monomer) and reducing the transitionstate energy.34 To compare the influence of the hyperpolarity effect on the SARA ATRP of MA for the three glycols investigated (TEG, EG, and DEG), different polymerizations were carried out using the same molar ratio (8%) of glycol in the solvent mixture. The content of the remaining solvents was adjusted to achieve DMSO/BMIM-PF6 = 50/50 (v/v), because this ratio provided the fastest polymerization of MA by SARA ATRP in the binary mixture, as previously reported.26 The results (Figure 3a) showed that regardless the nature of the glycol

Figure 4. (a) Kinetic plots of conversion and ln[M]0/[M] vs time and (b) plot of number-average molecular weights (MnSEC) and Đ (Mw/ Mn) vs monomer conversion for the SARA ATRP of MA in DMSO/ BMIM-PF6/TEG = 45/45/10 (v/v/v) at 30 °C, using different SARA agents. Reaction conditions: [MA]0/[solvent] = 2/1 (v/v); [MA]0/ [EBiB]0/SARA agent]0/[CuBr2]0/[Me6TREN]0= 222/1/1/0.1/1.1.

polymerization rate and level of control as for sodium dithionate. For the Fe(0) catalytic system, the polymerization rate was 13 times faster than that observed in pure DMSO.4 The Cu(0)-mediated polymerization was faster than the Fe(0)mediated one, which is in agreement with other results reported in the literature for the SARA ATRP of MA.4,37,38 Nevertheless, regardless of the SARA agent used, the monomer reached high conversion and the control over the molecular weight was excellent (Figure 4b). The Cu(0)-mediated SARA ATRP was also tested using the three different glycols (EG, DEG, and TEG), and the results were similar in terms of polymerization features (Figure S1), proving the versatility of the system. “Flash” SARA ATRP in Water/BMIM-PF6/TEG Mixtures. Because an increase in the polarity of the medium appeared to contribute to faster polymerizations, DMSO was replaced by water in the solvent reaction mixture to investigate its influence on the polymerization features. The replacement of DMSO is also attractive, considering the growing concerns about the environmental hazards derived from the use of organic solvents and due to the raising interest in polymerizations using ecofriendly solvents. The SARA ATRP of MA was performed using a H2O/BMIM-PF6/TEG = 10/45/45 (v/v) mixture. The content of water was limited to 10% to afford a homogeneous polymerization, considering that water is not miscible with BMIM-PF6 and PMA is insoluble in water. The kinetic results presented in Figure 5a (black symbols) show an extremely fast

Figure 3. (a) Kinetic plots of conversion and ln[M]0/[M] vs time and (b) plot of number-average molecular weights (MnSEC) and Đ (Mw/ Mn) vs monomer conversion for the SARA ATRP of MA in DMSO/ BMIM-PF6/TEG = 45/45/10 (v/v/v), DMSO/BMIM-PF6/EG = 48/ 48/4 (v/v/v), and DMSO/BMIM-PF6/DEG = 46/46/8 (v/v/v) at 30 °C: TEG (red symbols), EG (black symbols), and DEG (green symbols). Reaction conditions: [MA]0/[solvent] = 2/1 (v/v); [MA]0/ [EBiB]0/[Na2S2O4]0/[CuBr2]0/[Me6TREN]0= 222/1/1/0.1/0.2.

used, the DMSO/BMIM-PF6/glycol ternary mixtures allowed faster reactions when compared with the binary DMSO/ BMIM-PF6 = 50/50 (v/v) mixture,26 suggesting that the synergistic effect within the components of the solvent mixture could have a direct influence on the polymerization rate. Additionally, Figure 3a shows a linear first-order kinetic in respect to monomer conversion, which is typical of a controlled polymerization. Remarkably, even with high polymerization rate and monomer conversions near 100%, the level of control obtained was excellent (Đ < 1.1 during the entire polymerC

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polarity with the increase of the monomer conversion during the polymerization (Figure S2). In the case of this H2O/ BMIM-PF6/TEG mixture, besides the evident synergistic effect (Figure 6), one might expect that the activity of Cu(I) could be also very high because of the presence of water, leading to ultrafast reactions (4 times higher than in DMSO/BMIM-PF6/ TEG mixtures). Another explanation for the observed ultrafast polymerization (Figure 5) might be the increased solubility of the SARA agent (Na2S2O4) in the reaction mixture due to the presence of both water and TEG. The confirmation of these hypotheses requires further investigation, namely, the determination of the ka value. Regarding the DMSO/BMIM-PF6/TEG mixtures, the addition of monomer did not affect the hyperpolarity effect (Figure S3). “Livingness” of the PMA-Br. One-pot chain extension experiment was performed to prove the “living” character of the PMA-Br obtained by “flash” SARA ATRP. The SEC trace of the PMA-Br macroinitiator (Figure 7, black line) exhibits a

Figure 5. (a) Kinetic plots of conversion and ln[M]0/[M] vs time and (b) plot of number-average molecular weights (MnSEC) and Đ (Mw/ Mn) vs monomer conversion for the SARA ATRP of MA in H2O/ BMIM-PF6/TEG = 10/45/45 (v/v/v) at 30 °C. Reaction conditions: [MA] 0 /[solvent] = 2/1 (v/v); [MA] 0 /[EBiB] 0 /[Na 2 S 2 O 4 ] 0 / [CuBr2]0/[Me6TREN]0= 1000 or 222/1/1/0.1/0.2; DP = [MA]0/ [EBiB]0.

polymerization, with monomer reaching near 100% of conversion in less than 15 min for a DP = 222 (DP, degree of polymerization). Despite the very high polymerization rate, the Đ of the polymers was below 1.1 during the entire reaction (Figure 5b), which is remarkable. To the best of our knowledge, this is the fastest controlled polymerization of MA obtained by ATRP-related processes. The system proved to be quite robust as a well-defined PMA with high molecular weight (MnSEC ≈ 60 000) was obtained in 1 h of reaction, using 100 ppm of copper (green symbols in Figure 5). The ET(30) experimental values were also determined for the H2O/BMIM-PF6/TEG solvent mixture, in order to confirm a possible hyperpolarity effect. Because the BMIM-PF6 and water are immiscible, it was not possible to determine the ET(30) value when the TEG content was 0% (separate component H2O/BMIM-PF6). Alternatively, MA was added to the mixtures, with the same solvent/monomer ratio used for the polymerizations, to provide homogeneous solutions allowing the determination of the ET(30) values. Figure 6 shows that

Figure 7. SEC traces of the PMA-Br macroinitiator before (black line) and after the chain extension experiment (red line).

slight shoulder for higher molecular weights, which was attributed to the occurrence of some side reactions due to the very high monomer conversion at the time of the second monomer addition (>97%). This resulted in a tailing effect for low molecular weights in the SEC trace of the extended polymer (Figure 7, red line). Nevertheless, the clear shift of the molecular weight distribution from the PMA-Br (MnSEC = 5.8 × 103; Đ = 1.23) macroinitiator to the extended PMA-Br (MnSEC = 41.3 × 103; Đ = 1.10) confirmed the living character of the polymer. The presence of the active chain-ends and the chemical structure of the polymer were confirmed by 1H NMR spectroscopy (Figure 8).

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Figure 6. Experimental ET(30) values of H2O/BMIM-PF6/TEG mixtures with Reichardt’s dye 30 (50 μM). Dashed line represents the theoretical ET(30) values for each solvent mixture.

CONCLUSIONS

A hyperpolarity effect within the DMSO/BMIM-PF6/glycol (glycol: TEG, DEG, or EG) ternary mixtures allowed the increase of the overall polymerization rate, in comparison with DMSO/BMIM-PF6 binary mixtures, for the SARA ATRP of MA at 30 °C. The molecular weight of the resultant PMA was well-controlled during the entire polymerization time (Đ < 1.1), and the polymer presented living features. The replacement of DMSO by water giving a H2O/BMIM-PF6/ TEG mixture dramatically accelerated the polymerization, providing the fastest ATRP of MA reported in the literature, which was termed “flash” SARA ATRP.

there is a synergistic effect within the H2O/BMIM-PF6/TEG mixtures, as the ET(30) values were always higher than the theoretical values (dashed line). However, no hyperpolarity effect was observed because the ET(30) values were always lower than the values of the separated components, regardless the content of TEG in the mixture. Therefore, as previously suggested, the dramatic increase in the polymerization rate should be a consequence of a combination of factors and not only due to the existence of a hyperpolarity effect. Additional studies revealed that there was also an increase of the medium D

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Figure 8. 1H NMR spectrum (CDCl3) of a PMA-Br (MnSEC = 4.7 × 103; Đ = 1.11) obtained by “flash” SARA ATRP in H2O/BMIM-PF6/TEG = 10/45/45 (v/v).

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(10) Rocha, N.; Mendonça, P. V.; Mendes, J. P.; Simões, P. N.; Popov, A. V.; Guliashvili, T.; Serra, A. C.; Coelho, J. F. J. Macromol. Chem. Phys. 2013, 214 (1), 76−84. (11) Tom, J.; Hornby, B.; West, A.; Harrisson, S.; Perrier, S. Polym. Chem. 2010, 1 (4), 420−422. (12) Matyjaszewski, K.; Patten, T. E.; Xia, J. J. Am. Chem. Soc. 1997, 119 (4), 674−680. (13) Mendes, J. P.; Branco, F.; Abreu, C. M. R.; Mendonça, P. V.; Serra, A. C.; Popov, A. V.; Guliashvili, T.; Coelho, J. F. J. ACS Macro Lett. 2014, 3 (9), 858−861. (14) Percec, V.; Popov, A. V.; Ramirez-Castillo, E.; Monteiro, M.; Barboiu, B.; Weichold, O.; Asandei, A. D.; Mitchell, C. M. J. Am. Chem. Soc. 2002, 124 (18), 4940−4941. (15) Jakubowski, W.; Matyjaszewski, K. Angew. Chem. 2006, 118 (27), 4594−4598. (16) Zhang, Y.; Wang, Y.; Matyjaszewski, K. Macromolecules 2011, 44 (4), 683−685. (17) Matyjaszewski, K.; Jakubowski, W.; Min, K.; Tang, W.; Huang, J.; Braunecker, W. A.; Tsarevsky, N. V. Proc. Natl. Acad. Sci. U. S. A. 2006, 103 (42), 15309−15314. (18) Magenau, A. J. D.; Strandwitz, N. C.; Gennaro, A.; Matyjaszewski, K. Science 2011, 332 (6025), 81−84. (19) Treat, N. J.; Sprafke, H.; Kramer, J. W.; Clark, P. G.; Barton, B. E.; Read de Alaniz, J.; Fors, B. P.; Hawker, C. J. J. Am. Chem. Soc. 2014, 136 (45), 16096−16101. (20) Pan, X.; Lamson, M.; Yan, J.; Matyjaszewski, K. ACS Macro Lett. 2015, 4 (2), 192−196. (21) Abreu, C. M. R.; Serra, A. C.; Popov, A. V.; Matyjaszewski, K.; Guliashvili, T.; Coelho, J. F. J. Polym. Chem. 2013, 4 (23), 5629−5636. (22) Gois, J. R.; Konkolewic, D.; Popov, A. V.; Guliashvili, T.; Matyjaszewski, K.; Serra, A. C.; Coelho, J. F. J. Polym. Chem. 2014, 5 (16), 4617−4626. (23) Gois, J. R.; Rocha, N.; Popov, A. V.; Guliashvili, T.; Matyjaszewski, K.; Serra, A. C.; Coelho, J. F. J. Polym. Chem. 2014, 5 (12), 3919−3928. (24) Abreu, C. M. R.; Mendonça, P. V.; Serra, A. C.; Popov, A. V.; Matyjaszewski, K.; Guliashvili, T.; Coelho, J. F. J. ACS Macro Lett. 2012, 1 (11), 1308−1311. (25) Cordeiro, R. A.; Rocha, N.; Mendes, J. P.; Matyjaszewski, K.; Guliashvili, T.; Serra, A. C.; Coelho, J. F. J. Polym. Chem. 2013, 4 (10), 3088−3097. (26) Mendes, J. P.; Branco, F.; Abreu, C. M. R.; Mendonça, P. V.; Popov, A. V.; Guliashvili, T.; Serra, A. C.; Coelho, J. F. J. ACS Macro Lett. 2014, 3 (6), 544−547. (27) Sarkar, A.; Trivedi, S.; Pandey, S. J. Phys. Chem. B 2008, 112 (30), 9042−9049.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.5b01795.

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Kinetic data and UV−vis results (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The 1H NMR data were obtained at the Nuclear Magnetic Resonace Laboratory of the Coimbra Chemistry Centre (http://www.nmrccc.uc.pt), University of Coimbra, supported in part by Grant REEQ/481/QUI/2006 from FCT, POCI2010, and FEDER, Portugal.

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REFERENCES

(1) Braunecker, W. A.; Matyjaszewski, K. Prog. Polym. Sci. 2007, 32 (1), 93−146. (2) Matyjaszewski, K. Macromolecules 2012, 45 (10), 4015−4039. (3) Davis, K. A.; Paik, H.-j.; Matyjaszewski, K. Macromolecules 1999, 32 (6), 1767−1776. (4) Mendonça, P. V.; Serra, A. C.; Coelho, J. F. J.; Popov, A. V.; Guliashvili, T. Eur. Polym. J. 2011, 47 (7), 1460−1466. (5) Wang, J.-L.; Grimaud, T.; Matyjaszewski, K. Macromolecules 1997, 30 (21), 6507−6512. (6) Mendonca, P. V.; Konkolewicz, D.; Averick, S. E.; Serra, A. C.; Popov, A. V.; Guliashvili, T.; Matyjaszewski, K.; Coelho, J. F. J. Polym. Chem. 2014, 5 (19), 5829−5836. (7) Matyjaszewski, K.; Beers, K. L.; Muhlebach, A.; Coca, S.; Zhang, X.; Gaynor, S. G. Polym. Mater. Sci. Eng. 1998, 79, 429. (8) Rocha, N.; Mendes, J.; Duraes, L.; Maleki, H.; Portugal, A.; Geraldes, C. F. G. C.; Serra, A.; Coelho, J. J. Mater. Chem. B 2014, 2 (11), 1565−1575. (9) Xia, J.; Zhang, X.; Matyjaszewski, K. Macromolecules 1999, 32 (10), 3531−3533. E

DOI: 10.1021/acs.macromol.5b01795 Macromolecules XXXX, XXX, XXX−XXX

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Macromolecules (28) Sarkar, A.; Trivedi, S.; Baker, G. A.; Pandey, S. J. Phys. Chem. B 2008, 112 (47), 14927−14936. (29) Zhang, Y.; Wang, Y.; Peng, C.-h.; Zhong, M.; Zhu, W.; Konkolewicz, D.; Matyjaszewski, K. Macromolecules 2012, 45 (1), 78− 86. (30) Ciampolini, M.; Nardi, N. Inorg. Chem. 1966, 5 (1), 41−44. (31) Reichardt, C. Green Chem. 2005, 7 (5), 339−351. (32) Beniwal, V.; Kumar, A. ChemPhysChem 2015, 16 (5), 1026− 1034. (33) Harrisson, S.; Mackenzie, S. R.; Haddleton, D. M. Chem. Commun. 2002, 23, 2850−2851. (34) Harrisson, S.; Mackenzie, S. R.; Haddleton, D. M. Macromolecules 2003, 36 (14), 5072−5075. (35) Percec, V.; Grigoras, C. J. Polym. Sci., Part A: Polym. Chem. 2005, 43 (22), 5609−5619. (36) Yanagida, S.; Takahashi, K.; Okahara, M. Bull. Chem. Soc. Jpn. 1978, 51 (5), 1294−1299. (37) Guliashvili, T.; Mendonça, P. V.; Serra, A. C.; Popov, A. V.; Coelho, J. F. J. Chem. - Eur. J. 2012, 18 (15), 4607−4612. (38) Maximiano, P.; Mendes, J. P.; Mendonça, P. V.; Abreu, C. M. R.; Guliashvili, T.; Serra, A. C.; Coelho, J. F. J. J. Polym. Sci., Part A: Polym. Chem. 2015, DOI: 10.1002/pola.27736.

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DOI: 10.1021/acs.macromol.5b01795 Macromolecules XXXX, XXX, XXX−XXX