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     

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     

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 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     

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     

Preparation of polyacrylonitrile via SET‐LRP catalyzed by lanthanum powder in the presence of VC

A novel catalyst system based on La(0)/hexamethylenetetramine (HMTA) complexes is used for single electron transfer‐living radical polymerization (SET‐LRP) of acrylonitrile (AN) in the presence of ascorbic acid (VC) with carbon tetrachloride (CCl₄) as a initiator and N,N‐dimethylformamide (DMF) as a solvent. Compared with SET‐LRP of AN in the absence of VC, monomer conversion is markedly increased. SET‐LRP of AN in the presence of VC is also conducted in the presence of air. The kinetic studies show that the polymerizations both in the absence of oxygen and in the presence of air proceed in a well‐controlled manner. With the respect to the polymerization in the absence of oxygen, the polymerization in the presence of air provides slower reaction rate and broader polydispersity. Effects of amount of VC, La, CCl₄, and are investigated in detail. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4088–4094     

Acid dissolution of copper oxides as a method for the activation of Cu(0) wire catalyst for SET‐LRP

Here we reported the acid dissolution of copper oxides as a methodology for the activation of Cu(0) wire used as catalyst in single‐electron transfer living radical polymerization (SET‐LRP). In this method, the oxide layer on the surface of commercial Cu(0) wire was removed by dissolution in a concentrated acid such as nitric acid, glacial acetic acid and hydrochloric acid. SET‐LRP of methyl acrylate catalyzed with Cu(0) wire activated with acids showed comparable k value to that of the nonactivated Cu(0) wire‐catalyzed counterpart. However, the polymerizations catalyzed with activated Cu(0) wire proceeded with no initial induction period, predictable molecular weight evolution with conversion, and narrow molecular weight distribution. Regardless of the activation method, the chain end functionality of α,ω‐di(bromo) poly(methyl acrylate) (PMA) prepared from SET‐LRP initiated with a bifunctional initiator is extremely high, maintaining a 100% chain end functionality at ～90% monomer conversion. The degree of bimolecular termination increased as the polymerization exceeds 92% conversion. However, for binfunctional initiators this small amount of bimolecular termination at high conversion maintains a perfectly bifunctional polymer. Structural analysis by MALDI‐TOF upon thioetherification of α,ω‐di(bromo) PMA with thiophenol and 4‐fluorothiophenol confirmed the high fidelity of bromide chain ends. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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     

SET‐LRP of methyl acrylate to complete conversion with zero termination

The single electron transfer‐living radical polymerization of methyl acrylate (MA) initiated by bis(2‐bromopropionyl)ethane (BPE) in dimethyl sulfoxide was carried out to 100% monomer conversion and complete absence of bimolecular termination under the following reaction conditions: [MA]/[BPE]/[Me₆‐TREN]/[CuBr₂] = 60/1/0.21/0.01 and [MA]/[BPE]/[TREN]/[CuBr₂] = 60/1/0.25/0.05. These polymerizations were mediated by 0.5 cm of hydrazine‐activated Cu(0) wire of 20 gauge (0.812 cm in diameter), corresponding to a surface area of 0.14 cm² of Cu(0) per 3 mL reaction volume (2/1 v/v monomer/solvent). A higher extent of bimolecular termination (5–13%) was observed at complete conversion when longer lengths of Cu(0) wire were used. In the absence of CuBr₂ the activated Cu(0) wire/Me₆‐TREN catalyst in dimethyl sulfoxide also allowed the synthesis of perfectly bifunctional and monofunctional PMAs at complete conversion. This was also demonstrated by the quantitative reinitiation experiments from the chain(s) end(s) of these macroinitiators. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of well‐defined photoresist materials by SET‐LRP

Single electron transfer‐living radical polymerization (SET‐LRP) provides an excellent tool for the straightforward synthesis of well‐defined macromolecules. Heterogeneous Cu(0)‐ catalysis is employed to synthesize a novel photoresist material with high control over the molecular architecture. Poly(γ‐butyrolactone methacrylate)‐co‐(methyladamantly methacrylate) was synthesized. Kinetic experiments were conducted demonstrating that both monomers, γ‐butyrolactone methacrylate (GBLMA) and methyl adamantly methacrylate (MAMA), are successfully homopolymerized. In both cases polymerization kinetic is of first order and the molecular weights increase linearly with conversion. The choice of a proper solvent was decisive for the SET‐LRP process and organic solvent mixtures were found to be most suitable. Also, the kinetic of the copolymerization of GBLMA and MAMA was investigated. Following first order kinetics in overall monomer consumption and exhibiting a linear relationship between molecular weights and conversion a “living” process was established. This allowed for the straightforward synthesis of well‐defined photoresist polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2251–2255, 2010     

SET–LRP of N‐isopropylacrylamide in the presence of chain transfer agent

In this study, single electron transfer‐living radical polymerization (SET–LRP) of N‐isopropylacrylamide (NIPAM) in the presence of 2‐mercaptoethylamine chain transfer agent (CTA) was carried out by Cu(0) generated in situ from the disproportionation of CuBr/2,2′‐bipyridine (2,2′‐bpy) in N,N‐dimethylformamide (DMF) at 90 °C. Analysis of polymerization kinetics in the presence of CTA showed that the premature termination of growing polymer chains leads to retardation. The apparent rate constant of polymerization (k) decreased from 4.49 × 10^?4 to 2.59 × 10^?4 min^?1 with increasing CTA concentration. The initiator efficiency (I_eff) and the chain transfer constant (C_s) were found to be 0.524 and 0.286, respectively. The molecular weights of poly(N‐isopropylacrylamide) [poly(NIPAM)] produced were significantly higher than the predicted values, and the polydispersities were less than 1.22. © 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     

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 poly(N‐isopropylacrylamide) with a low molecular weight and a low polydispersity index by single‐electron transfer living radical polymerization

The single‐electron transfer living radical polymerization (SET‐LRP) method in the presence of chain transfer agent was used to synthesize poly(N‐isopropylacrylamide) [poly(NIPAM)] with a low molecular weight and a low polydispersity index. This was achieved using Cu(I)/2,2′‐bipyridine as the catalyst, 2‐bromopropionyl bromide as the initiator, 2‐mercaptoethanol as the chain transfer agent (TH), and N,N‐dimethylformamide (DMF) as the solvent at 90 °C. The copper nanoparticles with diameters of 16 ± 3 nm were obtained in situ by the disproportionation of Cu(I) to Cu(0) and Cu(II) species in DMF at 22 °C for 24 h. The molecular weights of poly(NIPAM) produced were significantly higher than the theoretical values, and the polydispersities were less than 1.18. The chain transfer constant (C_tr) was found to be 0.051. Although the kinetic analysis of SET‐LRP in the presence of TH corroborated the characteristics of controlled/living polymerization with pseudo‐first‐order kinetic behavior, the polymerization also exhibited a retardation period (k > k_tr). The influence of molecular weight on lower critical solution temperature (LCST) was investigated by refractometry. Our experimental results explicitly elucidate that the LCST values increase slightly with decreasing molecular weight. Reversibility of solubility and collapse in response to temperature well correlated with increased molecular weight of poly(NIPAM). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Single electron transfer‐living radical polymerization of methyl methacrylate catalyzed by ytterbium powder

Zerovalent ytterbium (Yb) powder is firstly used as a catalyst in single electron transfer‐living radical polymerization of methyl methacrylate initiated by carbon tetrachloride in N, N‐dimethylformamide (DMF) and dimethyl sulfoxide, respectively. Polymerization proceeds in a “living”/controlled way as evidenced by kinetic studies and chain extension results, producing well‐defined polymers with controlled degree of polymerization and narrow molecular weight distribution. The apparent activation energy of polymerization in DMF is accounted to be 36.2 kJ/mol, and the energy of equilibrium state is calculated to be 13.9 kJ/mol. An increase in the concentration of Yb(0) yields a higher monomer conversion. It is observed that polymerization rate experiments a rapid increase in the presence of more polar solvent water, and increasing in the content of H₂O results in an increase in the apparent rate constant of polymerization, and a decrease in the molecular weight distribution. The reaction rate and molecular weight increase along with the decrease of DMF content. The effect of Yb(0) powder content, different ligands and concentration of initiator on the polymerization is also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of polyacrylonitrile by single‐electron transfer‐living radical polymerization using Fe(0) as catalyst and its adsorption properties after modification

Fe(0) was firstly used as single‐electron transfer‐living radical polymerization catalyst for acrylonitrile polymerization using carbon tetrachloride as initiator, hexamethylenetetramine as N‐ligand, and N,N‐dimethylformamide as the solvent at 65 °C. First‐order kinetic studies indicated that this polymerization proceeded in a “living”/controlled manner. The living nature of the polymerization was also confirmed by chain extension of methyl methacrylate with polyacrylonitrile (PAN) as macroinitiator. Furthermore, PAN was modified with NH₂OH·HCl to generate amidoxime groups for extraction of heavy metal ions (Hg²⁺) from aqueous solutions. Fourier transformed infrared spectroscopy was performed to characterize chemical composition and structure. The adsorption property of Hg²⁺ was investigated at different pH values of aqueous solutions and distilled water. The maximal saturated adsorption capacity of Hg²⁺ was 4.8 mmol g^?1. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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     

Immortal SET–LRP mediated by Cu(0) wire

Cu(0)‐wire/Me₆‐TREN is a well established catalyst for living radical polymerization via SET–LRP. Here, it is demonstrated that this polymerization is not just living, but it is in fact the first example of immortal living radical polymerization. The immortality of SET–LRP mediated with Cu(0) wire was demonstrated by attempting, in an unsuccessful way, to irreversible interrupt multiple times the polymerization via exposure to O₂ from air. SET–LRP indeed stopped each time when the reaction mixture was exposed to air. However, the SET–LRP reaction, was restarted each time after resealing the reaction vessel and reestablishing the catalytic cycle with the same Cu(0) wire, to produce the same conversion as in the conventional uninterrupted SET–LRP process. Despite the interruption by O₂, the reactivated SET–LRP had a good control of molecular weight, molecular weight evolution, and molecular weight distribution, with perfect retention of chain‐end fidelity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2716–2721, 2010