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Synthesis of Well-Defined Poly(acrylates) in Ionic Liquids via Copper(II)-Mediated Photoinduced Living Radical Polymerization Athina Anastasaki,†,‡ Vasiliki Nikolaou,† Gabit Nurumbetov,† Nghia P. Truong,‡ George S. Pappas,†,§ Nikolaos G. Engelis,† John F. Quinn,‡ Michael R. Whittaker,†,‡ Thomas P. Davis,*,†,‡ and David M. Haddleton*,†,‡ †

University of Warwick, Chemistry Department, Library Road, CV4 7AL Coventry, United Kingdom ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), 399 Royal Parade, Parkville, Victoria 3152, Australia § University of Warwick, Warwick Manufacturing Group, CV4 7AL Coventry, United Kingdom ‡

S Supporting Information *

ABSTRACT: Herein we report the photoinduced living radical polymerization of acrylates in a variety of ionic liquids (ILs). 1Ethyl-3-methylimidazolium ethyl sulfate [emim][EtSO4], 1-heptyl-3methylimidazolium bromide [C7mim][Br], 1-hexyl-3-methylimidazolium tetrafluoroborate [C6mim][BF4], 1-hexyl-3-methylimidazolium hexafluorophosphate [C6mim][PF6], and 1-octyl-3-methylimidazolium hexafluorophosphate [C8mim][PF6] were employed as solvents for the homopolymerization of a variety of acrylates including methyl acrylate (MA), n-butyl acrylate (n-BA), ethylene glycol methyl ether acrylate (EGA), and poly(ethylene glycol) methyl ether acrylate (PEGA, Mn ≈ 480). Polymerization of MA, EGA, and PEGA in [C6mim][BF4], [C6mim][PF6], and [C8mim][PF6] proceeded in a controlled manner, as evidenced by kinetic studies, narrow molecular weight distributions (Đ ≈ 1.1), and quantitative conversions (>99%) within 30 min. MALDI-ToF-MS and 1H NMR confirmed very high end-group fidelity, which was further exemplified by in situ chain extensions and block copolymerizations, yielding welldefined block copolymers in a quantitative manner. While polymerization of n-BA in [C6mim][BF4] and [C6mim][PF6] yielded polymers with bimodal molecular weight distribution (potentially due to poor solubility), polymerization of the same monomer in [C8mim][PF6] was well-controlled yielding materials with a monomodal polymer peak distribution and low dispersity. Interestingly, all polymerizations in ILs experienced a significant acceleration on the rate of polymerization without compromising the end-group fidelity, as opposed to the slower rates observed when DMSO was used as the solvent. The versatility of the approach was also demonstrated by polymerization of MA to a number of chain lengths (Mn ≈ 4500−40 000 g mol−1) furnishing poly(acrylates) with low dispersities in all cases (Đ ≈ 1.1). Importantly, extraction of the obtained polymer with toluene allowed the IL/catalyst solution to be reused as the solvent for further polymerizations without affecting the living nature of the polymerization. Moreover, the polymer extracted into the toluene (copper-free) can be used directly for postpolymerization modifications (e.g., click reactions).

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INTRODUCTION Living radical polymerization (LRP) has revolutionized the field of polymer science, providing access to polymers with predetermined molecular weight, narrow molecular weight distributions, high end-group fidelity, and complex architectures. Among numerous polymerization techniques,1−3 transition-metal-mediated living radical polymerization (TMMLRP), including atom transfer radical polymerization (ATRP)3,4 and single electron transfer living radical polymerization (SET-LRP),5,6 has significantly contributed toward this field. In TMMLRP, radical generation occurs via an alkyl halide undergoing a reversible redox process catalyzed by a transitionmetal compound such as Cu(I) or Cu(0). Importantly, the activation−deactivation equilibrium between propagating radicals and dormant species is exploited to invoke control over © 2015 American Chemical Society

the polymerization and provide rapid access to a large diversity of architectures such as stars, grafts, and multiblock copolymers.7−14 Ionic liquids (ILs) are organic salts that are liquid at ambient temperature and are usually composed of large organic cations and small inorganic or organic anions. Over the past few years, significant attention has been directed toward ILs due to their unique properties including low volatility, chemical stability, high conductivity, and wide electrochemical window.15,16 ILs are of considerable interest to synthetic chemists as replacement solvents for chemical reactions, including hydroReceived: June 2, 2015 Revised: June 30, 2015 Published: July 27, 2015 5140

DOI: 10.1021/acs.macromol.5b01192 Macromolecules 2015, 48, 5140−5147

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Macromolecules genation, alkylation, Diels−Alder coupling,17,18 and so on. One key advantage of using ILs for the synthesis of low-molecularweight compounds is that the products can be separated simply by evaporation, thus enabling the IL solution to be reused for subsequent reaction cycles.19,20 Aside from the obvious environmental benefits of such an approach, the large number of cations and anions that can be used in an IL provide for a wide range of physical and chemical characteristics allowing control over the reaction processing and solvent−solvent interactions to be tailored for the specific situation.16 To date, ILs have been applied to various LRP systems, including RAFT (introduced for the first time by Davis and coworkers)21,22 and NMP (developed by Mays, Aldabbagh, Zetterlund, Yamada, and coworkers).23,24 In the case of TMMLRP, the use of ILs was pioneered by Haddleton and coworkers,25 who utilized 1-butyl-3-methyl-imidazolium hexafluorophosphate [bmim][PF6] as the solvent for the CuIBrmediated LRM of methyl methacrylate (MMA), which demonstrated narrow molecular weight distributions (Đ ≈ 1.3) and relatively fast polymerization rates, as observed in other polar solvents. (Solvent-induced acceleration was also obtained during the free radical polymerization of MMA in ILs.)26 Although the polymer was recovered with only ppm levels of copper via a simple solvent wash, the recycling of the IL/catalyst mixture was not attempted.25 Matyjaszewski and coworkers subsequently reported the ATRP of MMA in the presence of ILs that could interact with the transition metal, thus providing an ATRP system that could operate in the absence of additional organic ligands.27 Percec et al. also reported the LRP of MMA in ILs catalyzed by the self-regulated Cu2O/2,2′-bipyridine system, demonstrating 100% initiator efficiency and yielding polymers with narrow molecular weight distributions;28 however, in all of the aforementioned reports, only methacrylates have been studied, and relatively fast polymerization rates (fastest achieved = 82% conversion in 1 h, Đ ≈ 1.36) were realized only at relatively high temperatures (∼70 °C), with substantial decrease in the rate observed at lower temperatures (∼22 °C). Moreover, chain extensions and block copolymerizations were not reported, and thus high endgroup fidelity was not further demonstrated. On a different note, Kubisa and coworkers investigated the ATRP of acrylates in ILs, although narrow molecular weight distributions were only observed for relatively low-molecular-weight polymers (Mn ≈ 1000−4000 g mol−1), and block formation could be achieved only upon purification of the macroinitiators.29,30 Recently, control of the activation/deactivation step via external regulation has attracted considerable interest.31−33 Among the various stimuli employed, light is perhaps the most attractive as it is environmentally friendly, noninvasive, and widely available. Several groups have contributed toward photochemical control of polymerizations, developing sophisticated systems that allow not only control over the molecular weight distributions but also spatiotemporal control upon demand.34−39 TMMLRP, in particular, has been shown to be compatible with photoirradiation with Yagci,40−42 Matyjaszewski,43,44 Haddleton,45−49 Junkers50,51 and coworkers reporting the sunlight and UV photopolymerizations in the presence of CuBr2 and various N-containing ligands. Herein, we present the photoinduced LRP of acrylates in ILs, in the presence of low concentration of CuBr2 and Me6-Tren under UV irradiation. The homopolymerization of a diverse range of acrylates (MA, n-BA, EGA, and PEGA) was attempted in five different ILs. Among them, [C6mim][BF4], [C6mim]-

[PF6], and [C8mim][PF6] facilitate the rapid polymerization of acrylates achieving full monomer conversion (>99%) in 99% conversion). A single polymer peak distribution was observed corresponding to PMA initiated by the EBiB fragment and terminated by a bromine atom (Figure 3a,b). In addition, 1 H NMR also indicated excellent end-group fidelity (>99%), as evaluated by comparison of the signals from the −CH3 groups of the isobutyrate group of EBiB (∼1.0 ppm) with the ωterminal methine signal from the polymer backbone (∼4.3 ppm) (Figure S2 in the SI). This high end group fidelity was verified by in situ chain extension of the PMA (99% conversion in 30 min, Đ ≈ 1.10) after the addition of a second aliquot of 5142


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Figure 3. (a,b) MALDI-ToF-MS analysis of PMA, (c) in situ chain extension, and (d) block copolymerization from a PMA macroinitiator. Initial conditions [MA]:[EBiB]:[CuBr2]:[Me6-Tren] = [50]:[1]:[0.02]:[0.12], [C6mim][BF4] (50% v/v).

MA without the requirement to purify the macroinitiator (Figure S4 in the SI). SEC analysis revealed a complete shift to higher molecular weights, while the molecular weight distributions remained narrow (Đ ≈ 1.10) (Figure 3c). The addition of a second aliquot of a different acrylic monomer (EGA or PEGA) resulted in a one-pot block copolymerization, furnishing a well-defined block copolymers with low dispersity values (Đ ≈ 1.12), even at high monomer conversion (>99%) (Figure 3d and Figures S5 and S6 in the SI). We were also interested in achieving higher molecular weight poly(acrylates), and thus PMA of higher molecular weight was also targeted (Mn = 15 100 g mol−1, DP = 200). A well-defined polymer with a narrow molecular weight distribution (Đ ≈ 1.10) was obtained within 30 min. In addition, when the chain length was extended to DP = 400, control of the polymerization was retained with good agreement between theoretical and experimental molecular weight and low dispersity (Đ ≈ 1.11). In both cases the polymerization was allowed to reach nearquantitative conversion (98%) prior to SEC analysis (Figures S7 and S8 in the SI). Thus, it was demonstrated that good control over the molecular weight distributions was not just limited to polymers with a low targeted molecular weight (Figure 4 and Table 2). The scope of the polymerization in [C6mim][BF4] was subsequently expanded utilizing a number of acrylic monomers including n-BA, EGA, and PEGA (Table 1). Both EGA and PEGA were polymerized successfully, exhibiting fast polymerization rates (∼30 min for the reaction to reach full conversion) and low dispersity values (Đ < 1.19) for the resulting polymer at quantitative or near-quantitative conversions, illustrating the robustness of the technique (Figures S10 and S11 in the SI).

Figure 4. SEC analysis of PMA with various DP prepared by photoinduced LRP in [C6mim][BF4].

Unfortunately, n-BA could not be successfully polymerized in a controlled manner using [C6mim][BF4], with SEC revealing bimodality (Figure S9 in the SI). This was attributed to the limited solubility of n-BA in this IL and will be addressed subsequently in the manuscript. The polymerization of acrylates in [C6mim][PF6] was also investigated. Again homopolymerization of MA proceeded quickly at ambient temperature, attaining high conversion (>99%) in 30 min (Figure S12 in the SI). SEC analysis revealed a linear increase in number-average molecular weight (Mn) with increasing conversion, excellent agreement with theoretical Mn, 5143


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Macromolecules Table 1. Summary of Photoinduced LRP of Various Acrylates in Ionic Liquids monomer

IL

t (min)

conv. (%)

Mn,th (g·mol−1)

Mn,SEC (g·mol−1)

Đ

MA DP = 50

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

35 960 35 960 35 35 960 35 960 35 960 960 960 960 35 35 960 35 960 35

>99 0 >99 11 99 99 0 99 45 >99 90 0 93 85 97 >99 99 99 0 98

4500

4900

1.14

4500 500 4500 6700

4800 1700 5100 7600

1.16 bimodal 1.07 1.12

6700 3000 6700 5900

7300 6000 6600 6200

1.17 bimodal 1.10 bimodal

6100 5600 6500 7300 7300 7300

6900 53000 6400 6900 8200 6800

bimodal bimodal 1.22 1.18 5.40 1.17

7200

8700

1.19

EGA DP = 50

n-BA DP = 50

PEGA DP = 15

Table 2. In Situ Chain Extensions and Block Copolymerizations of PMA in Ionic Liquids IL

block copolymer

t (min)

conv. (%)

Mn,th (g·mol−1)

Mn,SEC (g·mol−1)

Đ

1

PMA50-b-PMA50 PMA50-b-PEGA50 PMA50-b-PPEGA15 PMA200 PMA400 PMA50-b-PMA50 PMA50-b-PEGA50 PMA50-b-PPEGA15 PMA200 PMA400 PMA50-b-PMA50 PMA50-b-PEGA50 PMA50-b-PPEGA15 PMA50-b-PBA50 PMA200 PMA400

60 60 60 30 30 60 60 60 30 30 60 60 60 60 30 30

98 100 100 98 98 100 99 100 98 99 100 98 99 98 97 96

8600 11000 11700 16000 34000 8800 10900 11700 16000 34000 8800 11000 11500 10700 16800 32900

10000 11700 12900 15100 32600 9800 11700 13000 14800 32800 10900 12000 10500 10800 16000 27000

1.12 1.12 1.14 1.09 1.07 1.14 1.12 1.19 1.10 1.09 1.07 1.06 1.19 1.11 1.06 1.07

3

5

and low dispersity (Đ ≈ 1.16). Kinetic analysis confirmed a largely first-order reaction kinetics with monomer and propagating radical concentration (Figure 2b and Figure S13 in the SI). To further explore the degree of control obtained in this polymerization, we analyzed final polymer samples by MALDI-ToF-MS (Figure S14 in the SI). Only one major polymer peak distribution was detected that corresponds to ωbromo-terminated PMA, thus indicating high bromo end-group fidelity and minimal side reactions (i.e., chain transfer).54 The livingness/controlled character of the system was further supported by chain extension (with a second aliquot of MA) (Figure S15 in the SI) and block copolymerization with either EGA (Figure S16 in the SI) or PEGA (Figure S17 in the SI). In all cases, a clear shift to higher molecular weights was evident by SEC and no low- or high-molecular-weight shoulder could be observed, despite the in situ addition at full conversion of the macroinitiator (PMA > 99% conversion). Well-defined diblock homo/block copolymers (Đ ≈ 1.14) could be obtained without compromising the initial fast rate of polymerization, as

> 97% conversion could be achieved in 1 h of reaction time (Table 2). Subsequently, to probe the potential of this IL in the synthesis of higher molecular weight polymers, we targeted higher degrees of polymerization (DP = 200 and 400). The ratio of [CuBr2]:[Me6-Tren] = [1]:[6] was maintained for these polymerizations, resulting in high conversions within 30 min (∼97%) and narrow molecular weight distributions (Đ ≈ 1.10) (Table 2 and Figures S18 and S19 in the SI). Different acrylic monomers, including EGA and PEGA, were also polymerized furnishing well-defined homopolymers with good agreement between theoretical and experimental values and low dispersity (Đ < 1.17 in both cases). Similarly to [C6mim][BF4], [C6mim][PF6] was not suitable for the controlled polymerization of n-BA (Table 1 and Figures S20−S22 in the SI). To successfully catalyze the polymerization of n-BA, we envisaged that a more hydrophobic IL would be required. Hence, [C8mim][PF6] was selected for the polymerization of nBA. Indeed, utilizing this more hydrophobic reaction medium 5144


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Macromolecules the polymer retained solubility, with no phase separation observed throughout the polymerization. SEC revealed a monomodal peak distribution with low dispersity (Đ ≈ 1.22) (Table 1 and Figure S23 in the SI). Similarly, other acrylates (MA, EGA, PEGA) also presented narrow MWDs at quantitative or near-quantitative conversions (Figures S24− S26 in the SI), while the rate of the polymerization was rapid, achieving very high conversions within 30 min (Figure 2c and Figure S27 in the SI). Higher molecular weight polymers (Figures S28 and S29 in the SI) and block copolymerizations (Figures S30−S33 in the SI) were also successfully performed, evident of the high retention of end-group functionality during this polymerization (Table 2); however, when the polymerization of MA was attempted in [emim][EtSO4], no conversion was observed by 1H NMR, even when the reaction was left to proceed overnight (16 h). Similar results were obtained for nBA (no conversion), while the polymerization of PEGA was uncontrolled (Đ ≈ 4) (Figure S34 in the SI) and finally EGA showed poor solubility in the reaction medium. Polymerization of the aforementioned monomers in [C7mim][Br] was also unsuccessful with limited conversions or broad molecular weight distributions (Figures S35−S37 in the SI). Thus, it was concluded that both [emim][EtSO4] and [C7mim][Br] are unsuitable for the controlled polymerization of acrylates under the conditions employed due to the more coordinating nature of the anion. Importantly, ILs have attracted considerable interest as potential environmentally friendly solvents as they can be reused for organic reactions by evaporating the low-molecularweight compounds while maintaining the catalyst in the IL reaction mixture given their low vapor pressure; however, in polymer science, this convenient reaction methodology cannot be employed due to the nonvolatile nature of the polymers. To circumvent this, we must use organic solvents to isolate the polymer from the IL solution, and thus it can be argued that the advantage of using this environmentally friendly reaction medium is partly lost; however, in TMMLRP systems, the extraction of the polymer with an organic solvent can potentially maintain the catalyst in the IL solution and thus allow for the recycling of the catalytic system (CuBr2/Me6Tren). This is of considerable importance because N-containing ligands are typically the most expensive reagents in the polymerization. Thus, potential reuse of these compounds could be highly desirable. A further advantage of extracting the polymer with toluene (copper-free) is the possibility of subsequent post-polymerization modifications directly in the toluene solution without the need to remove the organic solvent (e.g., click reaction).55 To explore the possibility of reusing the IL solution, we extracted PMA from the polymerization solution ([C6mim][BF4] or [C6mim][PF6]) using toluene until 1H NMR of both phases confirmed complete extraction of the polymer into the toluene phase (i.e., no polymer was detected in the IL solution) (Figures S38 and S39 in the SI). The IL solution (which contains CuBr2/ Me6-Tren) was subsequently charged with additional initiator and monomer and deoxygenated, resulting in a well-defined homopolymer, which formed with similar polymerization rate, control over the molecular weight distribution, and molecular weight predictability as in the initial polymerization. This procedure (extraction/charging with new monomer-initiator) was repeated three times. In all cases, quantitative conversion was achieved within 1 h, while dispersity values remained as low as 1.12 (Figure 5). When the process was repeated for the

Figure 5. SEC analysis of PMA obtained from the recycling cycles of [C6mim][BF4].

fourth time, the polymerization rate was slightly decreased, requiring 2 h to reach full conversion. It should be noted that in the case of [C8mim][PF6] only one extraction cycle was successfully performed (98%, Mn = 5300, Đ = 1.07) (Figure S40 in the SI). This is most likely due to the more hydrophobic nature of this IL that disfavors the solubility of the CuBr2/Me6Tren catalyst. Nevertheless, it was clearly demonstrated that with appropriate selection of the IL it was possible for the IL/ catalyst to be recovered and reused several times without compromising the controlled/living features of the polymerizations.

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CONCLUSIONS The synthesis of well-defined poly(acrylates) in ILs via photoinduced LRP has been assessed and discussed. Five different ILs, including [emim][EtSO 4 ], [C 7 mim][Br], [C8mim][PF6], [C6mim][BF4], and [C6mim][PF6], were employed for the homopolymerization of MA, n-BA, EGA, and PEGA. The use of [EtSO4] and [Br] as counterions failed to mediate the controlled polymerization of acrylates under our reaction conditions while the use of the larger and less coordinating [BF4] and [PF6] allowed for the LRP of all monomers (with the exception of n-BA in [C6mim][BF4] and [C6mim][PF6]), presenting fast polymerization rates, quantitative conversions (>98% in 30 min), good control over the molecular weight distributions (Đ < 1.15), and high end-group fidelity, as evident by both 1H NMR and MALDI-ToF-MS analysis. This high end-group fidelity was exemplified by sequential in situ chain extensions and block copolymerizations, which lead to the synthesis of well-defined materials in a facile manner. Higher molecular weight polymers (Mn ≈ 40 000 g mol−1) were also targeted, maintaining high conversions and low dispersity. Importantly, the combination of ppm concentrations of catalyst via this photoinduced polymerization protocol with the recyclability of the IL/catalyst solution significantly contributes to the reduction of polymerization cost 5145


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(15) Ueki, T.; Watanabe, M. Macromolecules 2008, 41, 3739−3749. (16) Pârvulescu, V. I.; Hardacre, C. Chem. Rev. 2007, 107, 2615− 2665. (17) Earle, M. J.; McCormac, P. B.; Seddon, K. R. Green Chem. 1999, 1, 23−25. (18) Earle, M. J.; McCormac, P. B.; Seddon, K. R. Chem. Commun. 1998, 20, 2245−2246. (19) Kubisa, P. Prog. Polym. Sci. 2004, 29, 3−12. (20) Kubisa, P. Prog. Polym. Sci. 2009, 34, 1333−1347. (21) Perrier, S.; Davis, T. P.; Carmichael, A. J.; Haddleton, D. M. Chem. Commun. 2002, 2226−2227. (22) Perrier, S.; Davis, T. P.; Carmichael, A. J.; Haddleton, D. M. Eur. Polym. J. 2003, 39, 417−422. (23) Ryan, J.; Aldabbagh, F.; Zetterlund, P. B.; Yamada, B. Macromol. Rapid Commun. 2004, 25, 930−934. (24) Zhang, H.; Hong, K.; Mays, J. Polym. Bull. 2004, 52, 9−16. (25) Carmichael, A. J.; Haddleton, D. M.; Bon, S. A. F.; Seddon, K. R. Chem. Commun. 2000, 14, 1237−1238. (26) Harrisson, S.; Mackenzie, S. R.; Haddleton, D. M. Chem. Commun. 2002, 23, 2850−2851. (27) Sarbu, T.; Matyjaszewski, K. Macromol. Chem. Phys. 2001, 202, 3379−3391. (28) Percec, V.; Grigoras, C. J. Polym. Sci., Part A: Polym. Chem. 2005, 43, 5609−5619. (29) Biedroń, T.; Kubisa, P. Macromol. Rapid Commun. 2001, 22, 1237−1242. (30) Biedroń, T.; Kubisa, P. J. Polym. Sci., Part A: Polym. Chem. 2002, 40, 2799−2809. (31) Leibfarth, F. A.; Mattson, K. M.; Fors, B. P.; Collins, H. A.; Hawker, C. J. Angew. Chem., Int. Ed. 2013, 52, 199−210. (32) Magenau, A. J. D.; Strandwitz, N. C.; Gennaro, A.; Matyjaszewski, K. Science 2011, 332, 81−84. (33) Rzayev, J.; Penelle, J. Angew. Chem., Int. Ed. 2004, 43, 1691− 1694. (34) Fors, B. P.; Hawker, C. J. Angew. Chem., Int. Ed. 2012, 51, 8850− 8853. (35) Xu, J.; Jung, K.; Atme, A.; Shanmugam, S.; Boyer, C. J. Am. Chem. Soc. 2014, 136, 5508−5519. (36) Shanmugam, S.; Xu, J.; Boyer, C. Macromolecules 2014, 47, 4930−4942. (37) Treat, N. J.; Fors, B. P.; Kramer, J. W.; Christianson, M.; Chiu, C.-Y.; Alaniz, J. R. d.; Hawker, C. J. ACS Macro Lett. 2014, 3, 580−584. (38) 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, 16096−16101. (39) Shanmugam, S.; Xu, J.; Boyer, C. Chem. Sci. 2015, 6, 1341− 1349. (40) Yagci, Y.; Jockusch, S.; Turro, N. J. Macromolecules 2010, 43, 6245−6260. (41) Dadashi-Silab, S.; Atilla Tasdelen, M.; Yagci, Y. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2878−2888. (42) Tasdelen, M. A.; Ciftci, M.; Yagci, Y. Macromol. Chem. Phys. 2012, 213, 1391−1396. (43) Ribelli, T. G.; Konkolewicz, D.; Bernhard, S.; Matyjaszewski, K. J. Am. Chem. Soc. 2014, 136, 13303−13312. (44) Konkolewicz, D.; Schröder, K.; Buback, J.; Bernhard, S.; Matyjaszewski, K. ACS Macro Lett. 2012, 1, 1219−1223. (45) Anastasaki, A.; Nikolaou, V.; Zhang, Q.; Burns, J.; Samanta, S. R.; Waldron, C.; Haddleton, A. J.; McHale, R.; Fox, D.; Percec, V.; Wilson, P.; Haddleton, D. M. J. Am. Chem. Soc. 2013, 136, 1141−1149. (46) Anastasaki, A.; Nikolaou, V.; Simula, A.; Godfrey, J.; Li, M.; Nurumbetov, G.; Wilson, P.; Haddleton, D. M. Macromolecules 2014, 47, 3852−3859. (47) Anastasaki, A.; Nikolaou, V.; McCaul, N. W.; Simula, A.; Godfrey, J.; Waldron, C.; Wilson, P.; Kempe, K.; Haddleton, D. M. Macromolecules 2015, 48, 1404−1411. (48) Anastasaki, A.; Nikolaou, V.; Brandford-Adams, F.; Nurumbetov, G.; Zhang, Q.; Clarkson, G. J.; Fox, D. J.; Wilson, P.; Kempe, K.; Haddleton, D. M. Chem. Commun. 2015, 51, 5626−5629.

and thus paves the way for the inexpensive synthesis of welldefined materials.

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ASSOCIATED CONTENT

S Supporting Information *

Additional NMR, SEC, and MALDI-ToF-MS analysis spectra. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.5b01192.

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AUTHOR INFORMATION

Corresponding Authors

*D.M.H.: E-mail: [email protected]. *T.P.D.: E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Financial support by the University of Warwick, the Australian Research Council Centre of Excellence in Convergent BioNano Science and Technology (project number CE140100036), and Lubrizol are gratefully acknowledged. Equipment used in this research was supported by the Innovative Uses for Advanced Materials in the Modern World (AM2), with support from Advantage West Midlands (AWM), and partially funded by the European Regional Development Fund (ERDF). D.M.H. is a Royal Society/ Wolfson Fellow.

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REFERENCES

(1) 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, 5559−5562. (2) Hawker, C. J.; Bosman, A. W.; Harth, E. Chem. Rev. 2001, 101, 3661−3688. (3) Wang, J.-S.; Matyjaszewski, K. J. Am. Chem. Soc. 1995, 117, 5614−5615. (4) Kato, M.; Kamigaito, M.; Sawamoto, M.; Higashimura, T. Macromolecules 1995, 28, 1721−1723. (5) Percec, V.; Guliashvili, T.; Ladislaw, J. S.; Wistrand, A.; Stjerndahl, A.; Sienkowska, M. J.; Monteiro, M. J.; Sahoo, S. J. Am. Chem. Soc. 2006, 128, 14156−14165. (6) Zhang, Q.; Wilson, P.; Li, Z.; McHale, R.; Godfrey, J.; Anastasaki, A.; Waldron, C.; Haddleton, D. M. J. Am. Chem. Soc. 2013, 135, 7355− 7363. (7) Anastasaki, A.; Waldron, C.; Wilson, P.; Boyer, C.; Zetterlund, P. B.; Whittaker, M. R.; Haddleton, D. ACS Macro Lett. 2013, 2, 896− 900. (8) Boyer, C.; Soeriyadi, A. H.; Zetterlund, P. B.; Whittaker, M. R. Macromolecules 2011, 44, 8028−8033. (9) Soeriyadi, A. H.; Boyer, C.; Nyström, F.; Zetterlund, P. B.; Whittaker, M. R. J. Am. Chem. Soc. 2011, 133, 11128−11131. (10) Whittaker, M. R.; Urbani, C. N.; Monteiro, M. J. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 6346−6357. (11) Anastasaki, A.; Nikolaou, V.; Pappas, G. S.; Zhang, Q.; Wan, C.; Wilson, P.; Davis, T. P.; Whittaker, M. R.; Haddleton, D. M. Chem. Sci. 2014, 5, 3536−3542. (12) Zhang, Q.; Collins, J.; Anastasaki, A.; Wallis, R.; Mitchell, D. A.; Becer, C. R.; Haddleton, D. M. . Angew. Chem., Int. Ed. 2013, 52, 4435−4439. (13) Simula, A.; Nikolaou, V.; Anastasaki, A.; Alsubaie, F.; Nurumbetov, G.; Wilson, P.; Kempe, K.; Haddleton, D. M. Polym. Chem. 2015, 6, 2226−2233. (14) Waldron, C.; Anastasaki, A.; McHale, R.; Wilson, P.; Li, Z.; Smith, T.; Haddleton, D. M. Polym. Chem. 2014, 5, 892−898. 5146


Article

Macromolecules (49) Nikolaou, V.; Anastasaki, A.; Alsubaie, F.; Simula, A.; Fox, D.; Haddleton, D. Polym. Chem. 2015, 6, 3581−3585. (50) Wenn, B.; Conradi, M.; Carreiras, A. D.; Haddleton, D. M.; Junkers, T. Polym. Chem. 2014, 5, 3053−3060. (51) Chuang, Y.-M.; Ethirajan, A.; Junkers, T. ACS Macro Lett. 2014, 3, 732−737. (52) Ciampolini, M.; Nardi, N. Inorg. Chem. 1966, 5, 41−44. (53) D. Holbrey, J.; R. Seddon, K. J. Chem. Soc., Dalton Trans. 1999, 13, 2133−2140. (54) Anastasaki, A.; Waldron, C.; Wilson, P.; McHale, R.; Haddleton, D. M. Polym. Chem. 2013, 4, 2672−2675. (55) Bell, C. A.; Jia, Z.; Kulis, J.; Monteiro, M. J. Macromolecules 2011, 44, 4814−4827.

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