Alkyl chloride initiators for SET‐LRP of methyl acrylate

Single‐electron transfer living radical polymerization (SET‐LRP) proceeds by an outer‐sphere single‐electron transfer mechanism that induces a heterolytic bond cleavage of the initiating and propagating R‐X (where X = Cl, Br, and I) species. Therefore, unlike the homolytic bond cleavage mechanism claimed for ATRP, SET‐LRP is expected to show a small dependence of the nature of the halide group on the apparent rate constant of activation. This means the R‐X with X = Cl, Br, and I must all be efficient initiators for SET‐LRP and no chain transfer must be observed in the case of initiators with X = Br and I. Here, we report the SET‐LRP of methyl acrylate initiated with the alkyl chlorides methyl‐2‐chloropropionate (MCP) and chloroform (CHCl₃) and catalyzed by Cu(0)/Me₆‐TREN/CuCl₂ in DMSO at 25 °C. A combination of kinetic and structural analysis was used to elucidate the MCP and CHCl₃ initiating behavior under SET‐LRP conditions, and to demonstrate the very small dependence of the SET‐LRP apparent rate constant of propagation on X while providing polymers with well defined architecture. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4917–4926, 2008     

Ultrafast SET‐LRP of methyl acrylate at 25 °C in alcohols

Alcohols are known to promote the disproportionation of Cu(I)X species into nascent Cu(0) and Cu(II)X. Therefore, alcohols are expected to be excellent solvents that facilitate the single‐electron transfer mediated living radical polymerization (SET‐LRP) mediated by nascent Cu(0) species. This publication demonstrates the ultrafast SET‐LRP of methyl acrylate initiated with bis(2‐bromopropionyloxy)ethane and catalyzed by Cu(0)/Me₆‐TREN in methanol, ethanol, 1‐propanol, and tert‐butanol and in their mixture with water at 25 °C. The structural analysis of the resulting polymers by a combination of ¹H NMR and MALDI‐TOF MS demonstrates the synthesis of perfectly bifunctional α,ω‐dibromo poly(methyl acrylate)s by SET‐LRP in alcohols. Moreover, this work provides an expansion of the list of solvents available for SET‐LRP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2745–2754, 2008     

Synthesis of perfectly bifunctional polyacrylates by single‐electron‐transfer living radical polymerization

Poly(methyl acrylate)s, poly(ethyl acrylate)s, and poly(butyl acrylate)s with α,ω‐di(bromo) chain ends and M_n from 8500 to 35,000 were synthesized by single‐electron‐transfer living radical polymerization (SET‐LRP). The analysis of their chain ends by a combination of ¹H and 2D‐NMR, GPC, MALDI‐TOF MS, chain end functionalization, chain extension, and halogen exchange experiments demonstrated the synthesis of perfectly bifunctional polyacrylates by SET‐LRP. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4684–4695, 2007     

TREN versus Me6‐TREN as ligands in SET‐LRP of methyl acrylate

The commercially available tris(2‐aminoethyl)amine (TREN) was used as ligand to mediate the single‐electron transfer‐living radical polymerization (SET‐LRP) of methyl acrylate in dimethyl sulfoxide initiated with the bifunctional initiator bis(2‐bromopropionyl)ethane and catalyzed by both nonactivated and activated Cu(0) wire. A comparative study between TREN and tris(2‐dimethylaminoethyl)amine (Me₆‐TREN) ligand, that is more commonly used in SET‐LRP, demonstrated that TREN provided a slower polymerization but the chain‐ends functionality of the resulting bifunctional poly(methyl acrylate) was near quantitative and comparable to that obtained when Me₆‐TREN was used as a ligand. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012.     

SET‐LRP of acrylates in the presence of radical inhibitors

The Cu(0)/Me₆‐TREN‐catalyzed single‐electron transfer mediated living radical polymerization (SET‐LRP) of methyl acrylate in the presence of the classic 4‐methoxyphenol free radical inhibitor was investigated. Kinetic experiments, combined with ¹H NMR, and MALDI‐TOF MS analysis of the resulting polyacrylates demonstrated that SET‐LRP is a robust synthetic method that does not require the purification of the monomers to remove the radical inhibitor. It is anticipated that these results will contribute to the expansion of technological and fundamental applications of SET‐LRP since it allows the synthesis of polymers with a structural perfection that previously was not accessible by any other method, starting from unpurified monomers, solvents, initiators, and ligands. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3174–3181, 2008     

o‐nitrobenzyl acrylate is polymerizable by single electron transfer‐living radical polymerization

Polymers containing o‐nitrobenzyl esters are promising for preparation of light sensitive materials. o‐Nitrobenzyl methacrylate has already been polymerized by controlled ATRP or RAFT. Unfortunately, the radical polymerization of o‐nitrobenzyl acrylate (NBA) was not controlled until now due to inhibition and retardation effects coming from the nitro‐aromatic groups. Recent developments in the Single Electron Transfer–Living Radical Polymerization (SET–LRP) provide us an access to control this NBA polymerization and living character of this NBA SET–LRP is demonstrated. Effects of CuBr₂ and ligand concentrations, as well as Cu(0) wire length on SET–LRP kinetics are shown presently. A first‐order kinetics with respect to the NBA concentration is observed after one induction period. SET–LRP proceeds with a linear evolution of molecular weight and a narrow distribution. High initiation efficiency close to 1 and high chain‐end functionality (～93%) are reached. Chain extension of poly(o‐nitrobenzyl acrylate) is realized with methyl acrylate (MA) to obtain well defined poly(o‐nitrobenzyl acrylate)‐b‐poly(methyl acrylate) (PNBA‐b‐PMA). Finally, light‐sensitive properties of PNBA are checked upon UV irradiation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2192–2201     

Dramatic acceleration of SET‐LRP of methyl acrylate during catalysis with activated Cu(0) wire

A simple method for the activation of the Cu(0) wire used as catalyst in single‐electron transfer living radical polymerization (SET‐LRP) is reported. The surface of Cu(0) stored in air is coated with a layer of Cu₂O. It is well established that Cu₂O is a less reactive catalyst for SET‐LRP than Cu(0). We report here the activation of the Cu(0) wire under nitrogen by the reduction of Cu₂O from its surface to Cu(0) by treatment with hydrazine hydrate. The kinetics of SET‐LRP of methyl acrylate (MA) catalyzed with activated Cu(0) wire in dimethyl sulfoxide (DMSO) at 25 °C demonstrated a dramatic acceleration of the polymerization and the absence of the induction period observed during SET‐LRP catalyzed with nonactivated Cu(0) in several laboratories. Exposure of the activated Cu(0) wire to air results in a lower apparent rate constant of propagation because of gradual oxidation of Cu(0) to Cu₂O. This dramatic acceleration of SET‐LRP is similar to that observed with commercial Cu(0) nanopowder except that the polymerization provides excellent molecular weight evolution, very narrow molecular weight distribution and high polymer chain‐end functionality. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

The application of copper(II) deactivator on the single‐electron transfer living radical polymerization of tert‐butyl acrylate

We demonstrate the living radical polymerization of tert‐butyl acrylate (tBA) applying the SET mechanism, employing methyl 2‐bromopropionate (MBP) as initiator in dimethyl sulfoxide (DMSO) at ambient temperature. It is observed that introducing copper bromide into the catalyst system is necessary for controlling on the SET‐LRP polymerization of tBA. In this work, we make major investigation for the effect of the different stoichiometry quantity of copper bromide on the polymerization. Experiments show that the polymerization achieves better control with increasing the stoichiometry quantity of copper(II) deactivator. The structural analysis of the resulting polymers by ¹H NMR demonstrates the successful synthesis of poly(tBA)s by SET‐LRP in DMSO. Moreover, this work is helpful to the SET‐LRP of other monomers and is expected to expand the application of SET‐LRP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2793–2797, 2010     

SET‐LRP of acrylates in air

Single Electron Transfer‐Living Radical Polymerization (SET‐LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with well defined topology. In SET‐LRP, certain combinations of solvents and ligands facilitate the disproportionation of in situ generated Cu(I) species into “nascent” Cu(0) and Cu(II) species. A combination of heterogeneous and “nascent” Cu(0) activation yields polymers with very high chain end functionality. Under suitable conditions the tolerance toward oxygen must be increased since Cu(0), the activator in SET‐LRP, acts as an oxygen scavenger in all inert gas purification systems. Here we demonstrate that SET‐LRP of methyl acrylate can be conducted in the presence of air. The addition of a small amount of reducing agent hydrazine hydrate to the reaction mixture reduces Cu₂O generated by the oxidation of Cu(0) with air, regenerating Cu(0) and allowing for the synthesis of polymers with predictable molecular weight and perfect retention of chain end functionality. The kinetics plots obtained under these conditions were identical to these generated by degassed samples. High conversions were achieved within a very short reaction time. In these SET‐LRP experiments, the reagents were not deoxygenated or subjected to standard degassing procedures such as freeze‐pump‐thaw or nitrogen sparging. This simple SET‐LRP procedure provides an efficient and economical approach to the synthesis of functional macromolecules. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1190–1196, 2010     

Synthesis of well‐defined pH‐responsive PPEGMEA‐g‐P2VP double hydrophilic graft copolymer via sequential SET‐LRP and ATRP

A series of well‐defined double hydrophilic graft copolymers containing poly(poly(ethylene glycol) methyl ether acrylate) (PPEGMEA) backbone and poly(2‐vinylpyridine) (P2VP) side chains were synthesized by successive single electron transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET‐LRP of poly(ethylene glycol) methyl ether acrylate (PEGMEA) macromonomer using CuBr/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained homopolymer then reacted with lithium diisopropylamide and 2‐chloropropionyl chloride at ?78 °C to afford PPEGMEA‐Cl macroinitiator. poly(poly(ethylene glycol) methyl ether acrylate)‐g‐poly(2‐vinylpyridine) double hydrophilic graft copolymers were finally synthesized by. ATRP of 2‐vinylpyridine initiated by PPEGMEA‐Cl macroinitiator at 25 °C using CuCl/hexamethyldiethylenetriamine as catalytic system via the grafting‐ from strategy. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept relatively narrow (M_w/M_n ≤ 1.40). pH‐Responsive micellization behavior was investigated by ¹H NMR, dynamic light scattering, and transmission electron microscopy and this kind of double hydrophilic graft copolymer aggregated to form micelles with P2VP‐core while pH of the aqueous solution was above 5.0. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of high glass transition temperature copolymers based on poly(vinyl chloride) via single electron transfer—Degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of vinyl chloride in water

α,ω‐di(iodo) poly(isobornyl acrylate) macroiniators (α,ω‐di(iodo)PIA) with number average molecular weight from M _n,TriSEC = 11,456 to M _n,TriSEC = 94,361 were synthesized by single electron transfer‐degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of isobornyl acrylate (IA) initiated with iodoform (CHI₃) and catalyzed by sodium dithionite (Na₂S₂O₄) in water at 35 °C. The plots of number average molecular weight vs conversion and ln{[M]₀/[M]} vs time are linear, indicating a controlled polymerization. α,ω‐di(iodo) poly(isobornyl acrylate) have been used as a macroinitiator for the SET‐DTLRP of vinyl chloride (VCM) leading to high T_g block copolymers PVC‐b‐PIA‐b‐PVC. The dynamic mechanical thermal analysis of the block copolymers suggests just one phase indicating that copolymer behaves as a single material. This technology provides the possibility of synthesizing materials based on PVC with higher T_g in aqueous medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Thermoresponsive PPEGMEA‐g‐PPEGEEMA well‐defined double hydrophilic graft copolymer synthesized by successive SET‐LRP and ATRP

A series of well‐defined double hydrophilic graft copolymers containing poly[poly(ethylene glycol) methyl ether acrylate] (PPEGMEA) backbone and poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) side chains were synthesized by the combination of single electron transfer‐living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET‐LRP of poly(ethylene glycol) methyl ether acrylate macromonomer using CuBr/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained comb copolymer was treated with lithium diisopropylamide and 2‐bromoisobutyryl bromide to give PPEGMEA‐Br macroinitiator. Finally, PPEGMEA‐g‐PPEGEEMA graft copolymers were synthesized by ATRP of poly(ethylene glycol) ethyl ether methacrylate macromonomer using PPEGMEA‐Br macroinitiator via the grafting‐from route. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept narrow (M_w/M_n ≤ 1.20). This kind of double hydrophilic copolymer was found to be stimuli‐responsive to both temperature and ion (0.3 M Cl^? and SO). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 647–655, 2010     

SET‐LRP of vinyl chloride initiated with CHBr3 in DMSO at 25 °C

The development of Cu(0)/TREN/CuBr₂‐catalyzed SET‐LRP of VC initiated with CHBr₃ in DMSO at 25 °C is reported. The use of CuBr₂ additive allows for the first LRP of low molecular weight VC (target DP = 100), as well as lower Cu powder loading levels, improved I_eff and control in the synthesis of higher molecular VC, targeted degree of polymerization = 350, 700, 1,000, 1,400. ¹H NMR and HSQC confirm the bifunctionality of CHBr₃ as an initiator and suggest that deleterious side‐reactions such as the formation of allylic chlorides occur primarily at the onset of the reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4130–4140, 2009     

SET‐LRP of methyl acrylate catalyzed with activated Cu(0) wire in methanol in the presence of air

Single electron transfer‐living radical polymerization (SET‐LRP) of methyl acrylate (MA) in methanol, catalyzed with nonactivated and activated Cu(0) wires, was performed in the presence of nondeoxygenated reagents and was investigated under a simple blanket of nitrogen. The addition of a small amount of hydrazine hydrate mediates the deoxygenation of the reaction mixture by the consumption of oxygen through its use to oxidize Cu(0) to Cu₂O, followed by the reduction of Cu₂O with hydrazine back to the active Cu(0) catalyst. SET‐LRP of MA in methanol in the presence of air requires a smaller dimension of Cu(0) wire, compared to the nonactivated Cu(0) wire counterpart. Activation of Cu(0) wire allowed the polymerization in air to proceed with no induction period, linear first‐order kinetics, linear correlation between the molecular weight evolution with conversion, and narrow molecular weight distribution. The retention of chain‐end functionality of α,ω‐di(bromo) poly(methyl acrylate) (PMA) prepared by SET‐LRP was demonstrated by a combination of experiments including ¹H NMR spectroscopy and matrix‐assisted laser desorption ionization–time of flight mass spectrometry after thioetherification of α,ω‐di(bromo) PMA with thiophenol. In SET‐LRP of MA in the presence of limited air, bimolecular termination is observed only above 85% conversion. However, for bifunctional initiators, the small amount of bimolecular termination observed at high conversion maintains a perfectly bifunctional polymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

SET‐LRP of methyl methacrylate initiated with sulfonyl halides

Single electron transfer‐living radical polymerization (SET‐LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The present article describes the polymerization of methyl methacrylate by SET‐LRP in protic solvent mixtures. Herein, the polymerization process was catalyzed by a straightforward Cu(0)wire/Me₆‐TREN catalyst while initiation was obtained by toluenesulfonyl chloride. All experiments were conducted at 50 °C and the living polymerization was demonstrated by kinetic evaluation of the SET‐LRP. The process follows first order kinetic until all monomer is consumed which was typically achieved within 4 h. The molecular weight increased linearly with conversion and the molecular weight distributions were very narrow with M_w/M_n ～ 1.1. Detailed investigations of the polymer samples by MALDI‐TOF confirmed that no termination took place and that the chain end functionality is retained throughout the polymerization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2236–2242, 2010     

Synthesis of PMHDO‐g‐PDEAEA well‐defined amphiphilic graft copolymer via successive living coordination polymerization and SET‐LRP

A series of well‐defined amphiphilic graft copolymer containing hydrophobic polyallene‐based backbone and hydrophilic poly(2‐(diethylamino)ethyl acrylate) (PDEAEA) side chains was synthesized by sequential living coordination polymerization of 6‐methyl‐1,2‐heptadiene‐4‐ol (MHDO) and single electron transfer‐living radical polymerization (SET‐LRP) of 2‐(diethylamino)ethyl acrylate (DEAEA). Ni‐catalyzed living coordination polymerization of MHDO was first performed in toluene to give a well‐defined double‐bond‐containing poly(6‐methyl‐1,2‐heptadiene‐4‐ol) (PMHDO) homopolymer with a low polydispersity (M_w/M_n = 1.10). Next, 2‐chloropropionyl chloride was used for the esterification of pendant hydroxyls in every repeating unit of the homopolymer so that the homopolymer was converted to PMHDO‐Cl macroinitiator. Finally, SET‐LRP of DEAEA was initiated by the macroinitiator in tetrahydrofuran/H₂O using CuCl/tris(2‐(dimethylamino)ethyl)amine as catalytic system to afford well‐defined PMHDO‐g‐PDEAEA graft copolymers (M_w/M_n ≤ 1.22) through the grafting‐from strategy. The critical micelle concentration (cmc) was determined by ?uorescence spectroscopy with N‐phenyl‐1‐naphthylamine as probe and the micellar morphology was visualized by transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

SET‐LRP of vinyl chloride initiated with CHBr3 and catalyzed by Cu(0)‐wire/TREN in DMSO at 25 °C

The single‐electron transfer living radical polymerization (SET‐LRP) of vinyl chloride (VC) initiated with CHBr₃ in dimethylsulfoxide (DMSO) at 25 °C was investigated using Cu(0) powder and Cu(0) wire as the catalyst. It was determined that living kinetics and high conversion are achieved only through the proper calibration of the ratio between Cu(0) and TREN and the concentration of VC in DMSO. For both Cu(0) powder and Cu(0) wire, optimum conversion was achieved with higher levels of TREN than reported in earlier preliminary reports and under more dilute conditions. Using these conditions, 85+% conversion of VC could be achieved with Cu(0) powder and wire to produce white poly(vinyl chloride) (PVC) with M_n = 20,000 and M_w/M_n = 1.4–1.6 in 360 min. The use of Cu(0) wire provides the most effective catalytic system for the LRP of PVC allowing for simple removal and recycling of the catalyst. In the Cu(0) wire‐catalyzed SET‐LRP of VC, the consumption of Cu(0) was monitored as a function of conversion. From these studies, it is evident that the catalyst can be recycled extensively before significant exchange of Cu(0) into Cu(II)X₂ and change in catalyst surface area is observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 164–172, 2010     

Cu(0) mediated polymerization in toluene using online rapid GPC monitoring

Polymerization of methyl acrylate (MA) catalyzed by Cu(0) is carried out in toluene using a range of alcohols and phenol as additives to facilitate the reaction. The polar/coordinating additives promote disproportionation of Cu(I) to Cu(0), the proposed active species in single electron transfer living radical polymerization (SET‐LRP), and Cu(II) whilst toluene maintains solubility of the reagents and products. In this work, the use of alcohols as additives is optimized. Polymerizations are monitored in real time using rapid chromatography to obtain conversion and molecular weight distribution data without the necessity of manual sampling. Rapid gel permeation chromatography with low angle laser light scattering detection is shown to be a viable method of obtaining molecular weight distribution data in real time compared with conventional analytical techniques. Moreover, the changes in CuBr₂ concentration during SET‐LRP reactions are monitored online using a photodiode array detector. Finally, the kinetics of SET‐LRP of MA using an ultra pure highly porous Cu(0) is performed and a detailed discussion on the role of Cu(II) is provided. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

PNIPAM‐b‐(PEA‐g‐PDMAEA) double‐hydrophilic graft copolymer: Synthesis and its application for preparation of gold nanoparticles in aqueous media

A series of well‐defined double‐hydrophilic graft copolymers, consisting of poly(N‐isopropylacrylamide)‐b‐poly(ethyl acrylate) (PNIPAM‐b‐PEA) backbone and poly(2‐(dimethylamino)ethyl acrylate) (PDMAEA) side chains, were synthesized by the combination of single‐electron‐transfer living radical polymerization (SET‐LRP) and atom‐transfer radical polymerization (ATRP). PNIPAM‐b‐PEA backbone was first prepared by sequential SET‐LRP of N‐isopropylacrylamide and 2‐hydroxyethyl acrylate at 25 °C using CuCl/tris(2‐(dimethylamino)ethyl)amine as catalytic system followed by the transformation into the macroinitiator by treating the pendant hydroxyls with 2‐chloropropionyl chloride. The final graft copolymers with narrow molecular weight distributions were synthesized by ATRP of 2‐(dimethylamino)ethyl acrylate initiated by the macroinitiator at 40 °C using CuCl/tris(2‐(dimethylamino)ethyl)amine as catalytic system via the grafting‐from strategy. These copolymers were employed to prepare stable colloidal gold nanoparticles with controlled size in aqueous solution without any external reducing agent. The morphology and size of the nanoparticles were affected by the length of PDMAEA side chains, pH value, and the feed ratio of the graft copolymer to HAuCl₄. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1811–1824, 2009