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 well‐defined amphiphilic graft copolymer bearing poly(2‐acryloyloxyethyl ferrocenecarboxylate) side chains via successive SET‐LRP and ATRP

A series of well‐defined ferrocene‐based amphiphilic graft copolymers, consisting of poly(N‐isopropylacrylamide)‐b‐poly(ethyl acrylate) (PNIPAM‐b‐PEA) backbone and poly(2‐acryloyloxyethyl ferrocenecarboxylate) (PAEFC) side chains, were synthesized by the combination of single‐electron‐transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). A new ferrocene‐based monomer, 2‐(acryloyloxy)ethyl ferrocenecarboxylate (AEFC), was prepared first and it can be polymerized via ATRP in a controlled way using methyl 2‐bromopropionate as initiator and CuBr/PMDETA as catalytic system in DMF at 40 °C. PNIPAM‐b‐PEA backbone was synthesized by sequential SET‐LRP of NIPAM and HEA at 25 °C using CuCl/Me₆TREN as catalytic system followed by the transformation into the macroinitiator by treating the pendant hydroxyls with α‐bromoisobutyryl bromide. The targeted well‐defined graft copolymers with narrow molecular weight distributions (M_w/M_n < 1.20) were synthesized via ATRP of AEFC initiated by the macroinitiator. The electro‐chemical behaviors of PAEFC homopolymer and PNIPAM‐b‐(PEA‐g‐PAEFC) graft copolymer were studied by cyclic voltammetry. Micellar properties of PNIPAM‐b‐(PEA‐g‐PAEFC) were investigated by transmission electron microscopy and dynamic light scattering. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4346–4357, 2009     

Copolymerization of methacrylic acid with methyl methacrylate by SET‐LRP

Single‐electron transfer living radical polymerization (SET‐LRP) has developed as a reliable, robust and straight forward method for the construction well‐defined polymers. To span an even larger variety of functional monomers, we investigated the copolymerization of methyl methacrylate with methacrylic acid by SET‐LRP. Copolymerizations were catalyzed by Cu(0)/Me₆‐TREN and performed in MeOH/H₂O mixtures at 50 °C. The SET‐LRP copolymerizations of varying methacrylic acid content were evaluated by kinetic experiments. At low (2.5%) and moderate (10%) MAA loadings, the copolymerizations obeyed perfect first order kinetics (k_p^app = 0.008 min^?1 and k_p^app = 0.006 min^?1) and exhibited a linear increase in molecular weights with conversion providing narrow molecular weight distributions. The SET‐LRP of MMA/25%‐MAA was found to be significantly slower (k_p^app = 0.0035 min^?1). However, a reasonable first‐order kinetics in monomer consumption was maintained, and the control of the polymerization process was preserved since the molecular weight increased linearly with conversion and could therefore be adjusted. This work demonstrates that the copolymerization of methacrylic acid by SET‐LRP is feasible and the design of well‐defined macromolecules comprising acidic functionality can be achieved. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of high performance polyacrylonitrile by RASA SET–LRP in the presence of Mg powder

High performance polyacrylonitrile (PAN) was prepared with Mg powder as both reducing agent (RA) and supplemental activator (SA) by single electron transfer‐living radical polymerization (RASA SET‐LRP). First‐order kinetics of polymerization with respect to monomer concentration, linear increase of molecular weight, and narrow polydispersity with monomer conversion, and the obtained high isotacticity PAN indicate that RASA SET‐LRP in the presence of Mg powder could simultaneously control molecular weight and tacticity of PAN. compared with that obtained with ascorbic acid (VC) as RA, an obvious increase in isotacticity of PAN was observed. the block copolymer pan‐b‐pAN with molecular weight at 112,460, polydispersity at 1.33, and isotacticity at 0.314 was successfully prepared. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3328–3332     

SET‐LRP synthesis of PMHDO‐g‐PNIPAM well‐defined amphiphilic graft copolymer

A well‐defined amphiphilic graft copolymer, consisting of hydrophobic polyallene‐based backbone and hydrophilic poly(N‐isopropylacrylamide) (PNIPAM) side chains, was prepared by the combination of living coordination polymerization, single electron transfer‐living radical polymerization (SET‐LRP), and the grafting‐from strategy. First, the double‐bond‐containing backbone was prepared by [(η³‐allyl)NiOCOCF₃]₂‐initiated living coordination polymerization of 6‐methyl‐1,2‐heptadiene‐4‐ol (MHDO). Next, the pendant hydroxyls in every repeating unit of poly(6‐methyl‐1,2‐heptadiene‐4‐ol) (PMHDO) homopolymer were treated with 2‐chloropropionyl chloride to give PMHDO‐Cl macroinitiator. Finally, PNIPAM side chains were grown from PMHDO backbone via SET‐LRP of N‐isopropylacrylamide initiated by PMHDO‐Cl macroinitiator in N,N‐dimethylformamide/2‐propanol using copper(I) chloride/tris(2‐(dimethylamino)ethyl)amine as catalytic system to afford PMHDO‐g‐PNIPAM graft copolymers with a narrow molecular weight distribution (M_w/M_n = 1.19). The critical micelle concentration (cmc) in water was determined by fluorescence probe technique and the effects of pH and salinity on the cmc of PMHDO‐g‐PNIPAM were also investigated. The micellar morphology was found to be spheres using transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

SET‐LRP of acrylonitrile catalyzed by tin powder

Sn(0)‐mediated single electron transfer‐living radical polymerization (SET‐LRP) of acrylonitrile (AN) with carbon tetrachloride (CCl₄) as initiator and hexamethylenetetramine (HMTA) as ligand in N, N‐dimethylformamide (DMF) was studied. The polymerization obeyed first order kinetic. The molecular weight of polyacrylonitrile (PAN) increased linearly with monomer conversion and PAN exhibited narrow molecular weight distributions. Increasing the content of Sn(0) resulted in an increase in the molecular weight and the molecular weight distribution. Effects of ligand and initiator were also investigated. The block copolymer PAN‐b‐polymethyl methacrylate with molecular weight at 126,130 and polydispersity at 1.36 was successfully obtained. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

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 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     

Successive SET‐LRP and ATRP synthesis of ferrocene‐based PPEGMEA‐g‐PAEFC well‐defined amphiphilic graft copolymer

A series of ferrocene‐based well‐defined amphiphilic graft copolymers, consisting of hydrophilic poly[poly(ethylene glycol) methyl ether acrylate] (PPEGMEA) backbone and hydrophobic poly(2‐acryloyloxyethyl ferrocenecarboxylate) (PAEFC) side chains were synthesized by successive single‐electron‐transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was prepared by SET‐LRP of PEGMEA macromonomer, and it was then treated with lithium di‐isopropylamide and 2‐bromopropionyl bromide at ?78 °C to give PPEGMEA‐Br macroinitiator. The targeted well‐defined graft copolymers with narrow molecular weight distributions (M_w/M_n ≤ 1.32) were synthesized via ATRP of AEFC initiated by PPEGMEA‐Br macroinitiator, and the molecular weights of the backbone and side chains were both controllable. The electro‐chemical behaviors of graft copolymers were studied by cyclic voltammetry, and it was found that graft copolymers were more difficult to be oxidized, and the reversibility of electrode process became less with raising the content of PAEFC segment. The effects of the preparation method, the length of hydrophobic PAEFC segment, and the initial water content on self‐assembly behavior of PPEGMEA‐g‐PAEFC graft copolymers in aqueous media were investigated by transmission electron microscopy. The morphologies of micelles could transform from cylinders to spheres or rods with changing the preparation condition and the length of side chains. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

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 methyl methacrylate initiated with CCl4 in the presence and absence of air

Single electron transfer‐living radical polymerization (SET‐LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The synthesis of poly(methyl methacrylate) via SET‐LRP in dimethyl sulfoxide (DMSO) by using CCl₄ as initiator is demonstrated in this work. Resorting to a rather simple Cu(0)/Me₆‐TREN catalyst a method was established that allowed for the straightforward design of well‐defined poly(methyl methacrylate). The reactions were performed at various temperatures (25, 50, 60, and 80 °C) and complete monomer conversion could be achieved. The polymerizations obeyed first order kinetic, the molecular weights increased linearly with conversion and the polymers exhibited narrow molecular weight distributions all indicating the livingness of the process. By providing a small amount of hydrazine to the reaction mixture the polymerization could be conducted in presence of air omitting the need for any elaborated deoxygenation procedures. This methodology offers an elegant way to synthesize functionalized poly(methyl methacrylate) with perfect control over the polymerization process as well as molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2243–2250, 2010     

Synthesis of zwitterionic polymer by SET‐LRP at room temperature in aqueous

The Cu⁰‐mediated single electron transfer‐living radical polymerization of acrylamide and N,N‐dimethyl‐N‐methacryloyloxyethyl‐N‐sulfobutyl ammonium in aqueous at 25 °C using 2‐chloropropionamide as initiator with Cu⁰ powder/tris‐(2‐dimethylamino ethyl)amine (Me₆‐TREN) as catalyst system is studied. The results showed the characteristic of the “living” polymerization that were the M_n of polymers increased linearly with monomer conversion and the ln([M]₀/[M]) increased linearly with time too, meanwhile the narrow molecular of weight distributions were found at most cases. Because of the high rate constant of propagation and bimolecular termination of the acrylamide, the external addition of CuCl₂ is required to mediate deactivation the early stage of polymerization. In addition, the disproportionation constant of Cu^IX/L in H₂O is higher than in other solvents and the coordination of amino group and Cu^II takes place easily, so the isopropanol or N,N‐dimethylformamide is added to control the polymerization. High conversions were achieved within short time and the polymers prepared showed good antipolyelectrolyte properties in inorganic salts solutions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

SET‐LRP of acrylonitrile in ionic liquids without any ligand

Use of ionic liquids as reaction media was investigated in the design of an environmentally friendly single electron transfer‐living radical polymerization (SET‐LRP) for acrylonitrile (AN) without any ligand by using Fe(0) wire as catalyst and 2‐bromopropionitrile as initiator. 1‐Methylimidazolium acetate ([mim][AT]), 1‐methylimidazolium propionate ([mim][PT]), and 1‐methylimidazolium valerate ([mim][VT]) were applied in this study. First‐order kinetics of polymerization with respect to the monomer concentration, linear increase of the molecular weight, and narrow polydispersity with monomer conversion showed the controlled/living radical polymerization characters. The sequence of the apparent polymerization rate constant of SET‐LRP of AN was k_app ([mim][AT]) > k_app ([mim][PT]) > k_app ([mim][VT]). The living feature of the polymerization was also confirmed by chain extensions of polyacrylonitrile with methyl methacrylate. All three ionic liquids were recycled and reused and had no obvious effect on the controlled/living nature of SET‐LRP of AN. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of linear and 4‐arm star block copolymers of poly(methyl acrylate‐b‐solketal acrylate) by SET‐LRP at 25 °C

The new SET‐LRP (using Cu(0) powder for organic synthesis) was successfully used to produce well‐defined linear and star homo‐ and diblock‐copolymers of PMA, PSA, and P(MA‐b‐GA)_n (where n = 1 or 4). The kinetic data showed that all SET‐LRP were first order and reached high conversions in a short period of time. The other advantage of using such a system is that the copper can easily be removed through filtration, allowing the production of highly pure polymer. The molecular weight distributions were well controlled with polydispersity indexes below 1.1 and the number‐average molecular weight close to theory, especially upon the addition of Cu(II)Br₂/Me₆‐TREN complex. The linear and star block copolymers were then hydrolyzed to produce the biocompatible amphiphilic P(MA‐b‐GA)_n, where the glycerol side‐groups make the outer block hydrophilic. These blocks were micellized into water and found to have a R_g/R_H equal to 0.8 and 1.59 for the liner and star blocks, respectively. This together with the TEM's supported that the linear blocks formed the classical core‐shell micelles, where as, the star blocks formed vesicles. We found direct support for the vesicle structure from a TEM where one vesicle squashed a second vesicle consistent with a hollow structure. Such vesicle structures have potential applications as delivery nanoscaled devices for drugs and other important biomolecules. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6346–6357, 2008     

Cellulose‐based macroinitiator for crosslinked poly(butyl methacrylate‐co‐pentaerythritol triacrylate) oil‐absorbing materials by SET‐LRP

Cellulose produced from cotton fibers was used as substrate for synthesis of oil‐absorbing materials by single electron transfer‐living radical polymerization. The cellulose macroinitiator was prepared by esterification of hydroxyl group with 2‐bromoisobutyryl bromide (BiBB), followed by grafting with butyl methacrylate (BMA) and pentaerythritol triacrylate (PETA) to render a three‐dimensional architecture. The polymerization was catalyzed by Cu(0) powder/hexamethylenetetramine (HMTA) and performed in N,N‐dimethylformamide (DMF). Effects of cellulose, catalyst, reaction temperature, and time were investigated in detail. The maximum oil absorption to chloroform and toluene could reach 29.0 and 15.4 g·g^?1, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of well‐defined PNIPAM‐b‐(PEA‐g‐P2VP) double hydrophilic graft copolymer via sequential SET‐LRP and ATRP and its “schizophrenic” Micellization behavior in aqueous media

A series of well‐defined double hydrophilic graft copolymers, consisting of poly(N‐isopropylacrylamide)‐b‐poly(ethyl acrylate) backbone and poly(2‐vinylpyridine) side chains, were synthesized by successive single‐electron‐transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was prepared by sequential SET‐LRP of N‐isopropylacrylamide and 2‐hydroxyethyl acrylate at 25 °C using CuCl/tris(2‐(dimethylamino)ethyl)amine as the catalytic system. The obtained diblock copolymer was transformed into the macroinitiator by reacting with 2‐chloropropionyl chloride. Next, grafting‐from strategy was used for the synthesis of poly(N‐isopropylacrylamide)‐b‐[poly(ethyl acrylate)‐g‐poly(2‐vinylpyridine)] double hydrophilic graft copolymer. ATRP of 2‐vinylpyridine was initiated by the macroinitiator at 25 °C using CuCl/hexamethyldiethylenetriamine as the catalytic system. The synthesis of both the backbone and the side chains are controllable. Thermo‐ and pH‐responsive schizophrenic micellization behaviors were investigated by ¹H NMR, fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. Unimolecular micelles with PNIPAM‐core formed in acidic environment (pH = 2) with elevated temperature (T ≥ 32 °C), whereas the aggregates turned into spheres with PEA‐g‐P2VP‐core accompanied with the lifting of pH values (pH ≥ 5.3) at room temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 15–23, 2010     

Samarium powder as catalyst for SET‐LRP of acrylonitrile in 1,1,1,3,3,3‐hexafluoro‐2‐propanol for control of molecular weight and tacticity

Samarium powder was applied as a catalyst for single electron transfer‐living radical polymerization (SET‐LRP) of acrylonitrile (AN) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) with 2‐bromopropionitrile as initiator and N,N,N′,N′‐tetramethylethylenediamine as ligand. First‐order kinetics of polymerization with respect to the monomer concentration, linear increase of the molecular weight with monomer conversion, and the highly syndiotactic polyacrylonitrile (PAN) obtained indicate that the SET‐LRP of AN could simultaneously control molecular weight and tacticity of PAN. An increase in syndiotacticity of PAN obtained in HFIP was observed compared with that obtained by SET‐LRP in N,‐N‐dimethylformamide (DMF). The syndiotacticity markedly increased with the HFIP volume. The syndiotacticity of PAN prepared by SET‐LRP of AN using Sm powder as catalyst in DMF was higher than that prepared with Cu powder as catalyst. The increase in syndiotacticity of PAN with Sm content was more pronounced than the increase in its isotacticity. The block copolymer PAN‐b‐polymethyl methacrylate (52,310 molecular weight and 1.34 polydispersity) was successfully prepared. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of well‐defined chitosan‐based tricomponent copolymers for constructing multifunctional delivery systems

Chitosan‐based tricomponent copolymers, chitosan‐g‐poly(ε‐caprolactone)‐(g‐poly(oligo(ethylene glycol) methacrylate)) (CS‐PCL‐POEGMA, CPP), are synthesized as multifunctional nanocarriers for antitumor therapy. 2‐Bromoisobutyric acid and PCL are first site‐specifically conjugated onto the hydroxy groups of chitosan backbone through conventional coupling chemistry to give CS‐PCL‐Br using sodium dodecyl sulfate–chitosan complex as an organosoluble intermediate. CPP‐PCL‐Br is further used for initiating the single electron transfer‐living radical polymerization of OEGMA in the mixed solvent of dimethyl sulfoxide and lactic acid, yielding CPP. One‐pot reaction of CPP with a small amount of NaN₃ under the catalysis of Cu(I)Br/tris‐(2‐dimethylaminoethyl)amine converts the bromo ends of POEGMA grafts to azide functionality, which is used for conjugation of folic acid targeting moiety via azide–alkyne click reactions. The resultant tricomponent copolymers can assemble into spherical micelles with the capacity of coincorporating indocyanine green and Doxorubicin through electrostatic and hydrophobic interactions, respectively. The dual‐agent‐loaded micelles display a combined effect for combating HepG2 cells when irradiated with near‐infrared laser. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012