Single Electron Transfer-living Radical Polymerization Research Articles

Cu(0)/2,6-bis (imino)pyridines catalyzed single-electron transfer-living radical polymerization of methyl methacrylate initiated with poly(vinylidene fluoride-co -chlorotrifluoroethylene)

A series of 2,6-bis(imino)pyridines, as common ligands for late transition metal catalyst in ethylene coordination polymerization, were successfully employed in single-electron transfer-living radical polymerization (SET-LRP) of methyl methacrylate (MMA) by using poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) as macroinitiator with low concentration of copper catalyst under relative mild-reaction conditions. Well-controlled polymerization features were observed under varied reaction conditions including reaction temperature, catalyst concentration, as well as monomer amount in feed. The typical side reactions including the chain-transfer reaction and dehydrochlorination reaction happened on P(VDF-co-CTFE) in atom-transfer radical polymerization process were avoided in current system. The relationship between the catalytic activity and the chemical structure of 2,6-bis(imino)pyridine ligands was investigated by comparing both the electrochemical properties of Cu(II)/2,6-bis(imino)pyridine and the kinetic results of SET-LRP of MMA catalyzed with different ligands. The substitute groups onto N-binding sites with proper steric bulk and electron donating are desirable for both high-propagation reaction rate and CCl bonds activation capability on P(VDF-co-CTFE). The catalytic activity of Cu(0)/2,6-bis(imino)pyridines is comparable with Cu(0)/2,2′-bipyridine under the consistent reaction conditions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4378–4388

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

Synthesis of Novel Cationic Copolymer Acrylamide/Acrylic Acid Ester by Single Electron Transfer Living Radical Polymerization in Aqueous Solution

The imidazole,acrylonitrile,bromooctane were used to synthesize a new cationic polymerizable ionic liquid surfactant named chlorinated-1-octyl-3-(4-butylacrylate-based) imidazole(PMOIH8).Using 2-chloropropylamide(MPC) as the initiator,Cu0 powder and tris-(2-dimethylamino ethyl) amine(Me6-TREN) as the catalyst,a new kind of copolymer acrylamide/acrylic ester was synthesized via single electron transfer living radical polymerization(SET-LRP) of acrylamide with PMOIH8.The resulting polymers were analyzed by FT-IR,MS and 1H NMR,and the results showed that the polymers were target products.The relative molecular mass and the distribution of the resulting polymer were determined by GPC.The relative molecular mass of polymers is within the ramge of 2 × 103 ～ 14 × 103,and the relative molecular mass distribution is within the range of 1.21 ～ 1.75.Various factors which might affect the SET-LRP such as catalyst and initiator were discussed.The results showed that as the amount of catalyst reduced,the polymerization rate decreased and the polymerization rate constant(kapp p) reduced from 0.0168 min-1 to 0.0065 min-1,while the relative molecular mass distribution M w/ Mn increased from 1.25 ～ 1.71 to 1.32 ～ 1.75,and the initiator efficiency decreased,Ieff = 90.24%.As the amount of initiator increased,the relative molecular mass distribution of the resulting polymer was narrower with Mw/ Mn reduced from 1.25 ～ 1.71 to 1.21 ～ 1.68,while the polymerization rate constant(Kapp p) increased from 0.0168 min-1 to 0.0201 min-1,and the initiator efficiency increased,Ieff = 93.17%.

Single electron transfer-living radical polymerization of acrylonitrile catalyzed by lanthanum powder

Single electron transfer-living radical polymerization of acrylonitrile catalyzed by lanthanum powder

Reversible-Deactivation Radical Polymerization in the Presence of Metallic Copper. Comproportionation–Disproportionation Equilibria and Kinetics

This article is the first in a series of papers, describing reversible-deactivation radical polymerization (RDRP) in the presence of metallic copper. The aim of these papers is to determine the proportions and roles of Cu0, CuIBr/L, and CuIIBr2/L, and the overall reaction mechanism. This paper is focused on the comproportionation and disproportionation equilibrium between Cu0, CuIBr/L and CuIIBr2/L in dimethyl sulfoxide (DMSO) for various surface areas of Cu0 and different ligand concentrations, in both the absence and presence of methyl acrylate (MA). Comproportionation dominated disproportionation when there was enough ligand present in the reaction medium to stabilize all soluble copper species. The relative amount of CuI at comproportionation/disproportionation equilibrium increased with ligand concentration. CuI represents approximately 99.95% of all soluble Cu species in MA/DMSO = 2/1 (v/v) at the ratio [Me6TREN]0:[CuIIBr2]0 = 6:1. Under typical polymerization conditions, there is essentially no disproportionation, since the ratio [Me6TREN]:[CuII] is very large, starting from infinity and decreasing down to 6.7, for ∼3% terminated chains under the initial conditions [MA]0:[MBrP]0:[Me6TREN]0 = 222:1:0.1, in 33.3% (v/v) DMSO, with excess Cu0. The kinetics of comproportionation and disproportionation were both slow, requiring hours to reach equilibrium. The apparent rate coefficients for comproportionation and disproportionation were calculated as kcompapp = 9.0 × 10–4 cm s–1 and kdispapp = 2.0 × 10–5 cm s–1 in DMSO, as well as 3.5 × 10–3 cm s–1 and 3.1 × 10–6 cm s–1 in MA/DMSO = 2/1 (v/v), respectively. The results of this study invalidate the assumption of instantaneous and complete disproportionation, proposed in single-electron transfer living radical polymerization (SET-LRP). These findings agree with Cu0 acting as a supplemental activator and reducing agent in atom transfer radical polymerization (SARA ATRP).

Single‐electron transfer‐living radical polymerization of oligo(ethylene oxide) methyl ether methacrylate in the absence and presence of air

ABSTRACTThe efficient Cu(0) wire‐catalyzed single‐electron transfer‐living radical polymerization (SET‐LRP) of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) in DMSO and binary mixtures of DMSO with H2O is reported. Addition of 10–80% H2O to DMSO resulted in an increase in the apparent rate constant of propagation ( ), corresponding to an increase in the polarity and extent of disproportionation. At higher H2O content, decreases, and in H2O is slightly lower than that in DMSO. This unexpected behavior was attributed to the physical inaccessibility of Cu(0) wire catalyst to the hydrophobic reactive centers of OEOMA and initiator which self‐assemble in H2O into micellar aggregates and vesicles. This hypothesis was confirmed by the faster polymerization in H2O than in DMSO during catalysis with Cu(0) nanoparticles generated by disproportionation of CuBr. SET‐LRP of OEOMA can be performed in protic and dipolar aprotic solvents in air by the addition of hydrazine hydrate. The polymerization exhibited no induction period and identical as in the degassed experiment, and led to polymers with narrow molecular weigh distribution. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3110–3122

Aqueous Copper-Mediated Living Polymerization: Exploiting Rapid Disproportionation of CuBr with Me6TREN

A new approach to perform single-electron transfer living radical polymerization (SET-LRP) in water is described. The key step in this process is to allow full disproportionation of CuBr/Me6TREN (TREN = tris(dimethylamino)ethyl amine to Cu(0) powder and CuBr2 in water prior to addition of both monomer and initiator. This provides an extremely powerful tool for the synthesis of functional water-soluble polymers with controlled chain length and narrow molecular weight distributions (polydispersity index approximately 1.10), including poly(N-isopropylacrylamide), N,N-dimethylacrylamide, poly(ethylene glycol) acrylate, 2-hydroxyethyl acrylate (HEA), and an acrylamido glyco monomer. The polymerizations are performed at or below ambient temperature with quantitative conversions attained in minutes. Polymers have high chain end fidelity capable of undergoing chain extensions to full conversion or multiblock copolymerization via iterative monomer addition after full conversion. Activator generated by electron transfer atom transfer radical polymerization of N-isopropylacrylamide in water was also conducted as a comparison with the SET-LRP system. This shows that the addition sequence of l-ascorbic acid is crucial in determining the onset of disproportionation, or otherwise. Finally, this robust technique was applied to polymerizations under biologically relevant conditions (PBS buffer) and a complex ethanol/water mixture (tequila).

Copper‐mediated controlled radical polymerization in continuous flow processes: Synergy between polymer reaction engineering and innovative chemistry

ABSTRACTCopper(0)‐mediated controlled radical polymerization (CRP), or single‐electron transfer‐living radical polymerization (SET‐LRP) is a robust and dynamic technique that has attracted considerable academic and industrial interest as a synthetic tool for novel value‐added materials. Although SET‐LRP possesses many advantages over other forms of CRP, this novel chemistry still requires concurrent engineering solutions for successful commercial application. In this highlight, the evolution of atom‐transfer radical polymerization chemistry and development in continuous processes is presented, leading to recent research on the use of SET‐LRP in continuous flow tubular reactors. The proofs of concept are reviewed, and remaining challenges and unexplored potential on the use of continuous flow processes with SET‐LRP as a powerful platform for the synthesis of novel polymeric materials are discussed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3081–3096

Biomimetic design of amphiphilic polycations and surface grafting onto polycarbonate urethane film as effective antibacterial agents with controlled hemocompatibility

ABSTRACTThe synthetic polycations are ideal candidates as antimicrobial agents, because they resemble natural antimicrobial peptides, but to render hemocompatibility to these materials is a great challenge. Herein, we used 2‐(tert‐butyl‐aminoethyl) methacrylate (TBAEMA), to synthesize its homopolymer and pegylated random and diblock copolymers with polyethyleneglycol methacrylate (PEGMA, Mn = 360 Da) by single‐electron transfer–living radical polymerization (SET‐LRP). In the second step, the secondary amino groups in the precursor polymers were quaternized with iodomethane and bromohexane, to obtain three series of quaternized polymers. The antimicrobial properties of these quaternized polymers were evaluated against Escherichia coli (E. coli), by studying the minimum inhibitory concentrations (MICs) which ranged between 32 and 200 mg L−1 and showed higher values for the quaternized random than the diblock copolymers. In addition to, we have also demonstrated the grafting of these polycations onto polycarbonate urethane film surfaces, which showed good killing efficacy against E. coli. Furthermore, the hemolysis of these materials was investigated against human red blood cells, which indicated that except the quaternized homopolymers that showed highest hemolysis, all other amphiphilic polycations exhibited very low hemolytic activity. Therefore, our designed materials with controlled structures and functionality, synthesized from cheaply available resources could serve as useful agents in the field of biomedicines and implantable materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3166–3176

Stimuli‐responsive diblock copolymer brushes via combination of “click chemistry” and living radical polymerization

ABSTRACTpH‐ and temperature‐responsive poly(N‐isopropylacrylamide‐block−4‐vinylbenzoic acid) (poly(NIPAAm‐b‐VBA)) diblock copolymer brushes on silicon wafers have been successfully prepared by combining click reaction, single‐electron transfer‐living radical polymerization (SET‐LRP), and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. Azide‐terminated poly(NIPAAm) brushes were obtained by SET‐LRP followed by reaction with sodium azide. A click reaction was utilized to exchange the azide end group of a poly(NIPAAm) brushes to form a surface‐immobilized macro‐RAFT agent, which was successfully chain extended via RAFT polymerization to produce poly(NIPAAm‐b‐VBA) brushes. The addition of sacrificial initiator and/or chain‐transfer agent permitted the formation of well‐defined diblock copolymer brushes and free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Ellipsometry, contact angle measurements, grazing angle‐Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy were used to characterize the immobilization of initiator on the silicon wafer, poly(NIPAAm) brush formation via SET‐LRP, click reaction, and poly(NIPAAm‐b‐VBA) brush formation via RAFT polymerization. The poly(NIPAAm‐b‐VBA) brushes demonstrate stimuli‐responsive behavior with respect to pH and temperature. The swollen brush thickness of poly(NIPAAm‐b‐VBA) brush increases with increasing pH, and decreases with increasing temperature. These results can provide guidance for the design of smart materials based on copolymer brushes. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2677–2685

Regulation of the thermal sensitivity of hydroxypropyl cellulose by poly(N-isopropylacryamide) side chains

Hydroxyproyl cellulose graft poly(N-isopropylacryamide) (HPC-g-PNIPAm) copolymers were synthesized by single-electron transfer living radical polymerization (SET-LRP) in water and THF mixture solvent and characterized. The controllability and polymerization rate of SET-LRP can be adjusted by the water/THF ratio in the mixture solvent. The monomer conversion rate is relatively low in the solvent with low water content. The thermal responsive property of HPC-g-PNIPAm copolymers in aqueous solution depends on the length of the graft chains. The relatively short PNIPAm side chains (<150 repeat units) can effectively regulate the low critical solution temperature (LCST) of the HPC-g-PNIPAm copolymers in aqueous solution due to the hydrophilic properties of the short PNIPAm chains. This work provides an approach for the regulation of the LCST to body temperature region by graft copolymerization.

Sequence‐Controlled Multi‐Block Glycopolymers to Inhibit DC‐SIGN‐gp120 Binding

Glycan–protein interactions are essential for many physiological processes including cell–cell recognition, cell adhesion, cell signalling, pathogen identification, and differentiation. Dendritic cell-specific intercellular adhesion molecule3-grabbing non-integrin (DC-SIGN; CD209) is a C-type lectin (carbohydrate-binding protein) present on both macrophages and dendritic cell subpopulations and plays a critical role in many cell interactions. DC-SIGN binds to microorganisms and host molecules by recognizing surface-rich mannose-containing glycans through multivalent glycan– protein interactions and serves as a target for several viruses, such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Carbohydrate-binding proteins (CBP) have been suggested as potential microbicides for the prevention of HIV infection. However, the isolation of natural CBPs is relatively difficult because of their hydrophilic nature and low affinity for the virus. 4] Thus, synthetic lectins are of interest for carbohydrate recognition studies. Alternatively, noncarbohydrate inhibitors of mammalian lectins can be used to prevent the interaction between DC-SIGN and gp120. The structures of these multivalent ligands have a great effect on carbohydrate binding to lectins, and the use of linear polymers to effectively inhibit lectin binding has been demonstrated by several research groups. Synthetic polymer chemistry has developed rapidly in recent years. Currently, polymerization of functional monomers with the desired chain length, structure, and composition is straightforward; whereas producing polymers with monomer sequence control remains challenging, which has implications for the controlled folding of synthetic macromolecules. There are a few recent reports where sufficient control has been achieved in controlling the monomer sequence along the polymer chain. To the best of our knowledge, this is the first report where some control over the relative position of the sugars is exhibited and their binding to the human lectin DC-SIGN is demonstrated. We have used a controlled polymerization technique, single-electron transfer living radical polymerization (SET-LRP), to polymerize glycomonomers, which are prepared by copper catalyzed azide–alkyne click (CuAAC) reaction prior to polymerization. A series of glycomonomers were prepared by reaction of 3-azidopropylacrylate (APA) and alkylated mannose, glucose, and fucose using a Fischer–Helferich glycosylation. This was performed using CuSO4 and sodium ascorbate in a methanol/water mixture (see the Supporting Information). SET-LRP of the glucose monomer (GluA) was performed in dimethylsulfoxide (DMSO) using a copper(0)/copper(II) and tris[2-(dimethylamino)ethyl]amine (Me6TREN)-derived catalyst. Polymerization reached over 90 % monomer conversion in six hours whilst maintaining a narrow molecular weight distribution with increasing molecular weight. (Supporting Information, Figure S4). The obtained polymers were characterized by size exclusion chromatography (SEC) and MALDI-TOF mass spectroscopy (MS) or high-resolution electrospray ionization mass spectroscopy (HR-ESI MS), which indicated very high chain-end fidelity allowing for sequential monomer addition. We designed a polymerization reaction starting with one equivalent of initiator (I) and two equivalents of mannose glycomonomer (ManA; Figure 1a). ManA was fully consumed after 12 hours; then two equivalents of GluA in DMSO were added to the reaction mixture and GluA was consumed in 16 hours. Two equivalents of ManA in DMSO were subsequently added to the reaction mixture, and this cycle was continued until six short blocks of glycopolymers were produced (the degree of polymerization (DP) = 2 for each block, (mannose)2-(glucose)2-(mannose)2-(glucose)2(mannose)2-(glucose)2). No purification steps were required prior to addition of the subsequent monomer. The conversion of the first four blocks, as analyzed by H NMR spectroscopy, reached 100 %, shown by the complete disappearance of vinyl groups at 5.7–6.5 ppm. The glycomonomers were dissolved in purged DMSO prior to their addition and this resulted in further dilution of the reaction mixture upon each monomer addition. Traces of vinyl groups could still be detected after [*] Q. Zhang, J. Collins, A. Anastasaki, Dr. C. R. Becer, Prof. D. M. Haddleton Department of Chemistry, University of Warwick Gibbet Hill Road, Coventry, CV4 7AL (UK) E-mail: d.m.haddleton@warwick.ac.uk Homepage: http://www.warwick.ac.uk/go/polymers Dr. R. Wallis Department of Biochemistry, University of Leicester Leicester, LE1 9HN (UK) Dr. D. A. Mitchell Clinical Sciences Research Institute, Warwick Medical School, University of Warwick Coventry, CV2 2DX (UK) [**] We acknowledge financial support from the University of Warwick and the China Scholarship Council. Equipment used in this research was funded by the Innovative Uses for Advanced Materials in the Modern World (AM2) with support from AWM and ERDF. D.M.H. is a Royal Society/Wolfson Fellow and C.R.B. is a Science City Senior Research Fellow. Dr. Christopher N. Scanlan has provided the gp120. Supporting information for this article (syntheses of all materials and details of the characterization methods) is available on the WWW under http://dx.doi.org/10.1002/anie.201300068. Angewandte Chemie

Synthesis of a well‐defined polyallene‐based amphiphilic graft copolymer via sequential living coordination polymerization and SET‐LRP

AbstractA well‐defined amphiphilic graft copolymer, poly(6‐methyl‐1,2‐heptadien‐4‐ol)‐g‐poly(2‐(dimethylamino)ethyl methacrylate) (PMHDO‐g‐PDMAEMA), has been synthesized by the combination of living coordination polymerization, single electron transfer‐living radical polymerization (SET‐LRP), and the grafting‐from strategy. PMHDO backbone containing double bonds and pendant hydroxyls was first prepared by [(η3‐allyl)NiOCOCF3]2‐initiated living coordination polymerization of 6‐methyl‐1,2‐heptadien‐4‐ol (MHDO) followed by treating the pendant hydroxyls with 2‐chloropropionyl chloride to give PMHDO‐Cl macroinitiator. SET‐LRP of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) was performed in THF/H2O using PMHDO‐Cl as macroinitiator and CuCl/Me6TREN as catalytic system to afford the well‐defined PMHDO‐g‐PDMAEMA graft copolymer with a narrow molecular weight distribution (Mw/Mn = 1.28). The grafting density was as high as 92%. The critical micelle concentration (cmc) in water was determined by fluorescence probe technique and the micellar morphology was preliminarily explored by transmission electron microscopy. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

SET-LRP synthesis of novel polyallene-based well-defined amphiphilic graft copolymers in acetone

A series of polyallene-based well-defined amphiphilic graft copolymers consisting of hydrophobic poly(6-methyl-1,2-heptadiene-4-ol) (PMHDO) backbone and hydrophilic poly(2-(dimethylamino)ethyl acrylate) (PDMAEA) side chains, was synthesized by the combination of living coordination polymerization and single-electron transfer living radical polymerization (SET-LRP). A double-bond-containing PMHDO backbone with pendant hydroxyls was prepared via [(η3-allyl)NiOCOCF3]2-initiated living coordination polymerization of a hydroxyl-containing allene derivative, 6-methyl-1,2-heptadiene-4-ol (MHDO). The pendant hydroxyls in the homopolymer were then treated with 2-chloropropionyl chloride to provide the PMHDO-Cl macroinitiator. Finally, the target PMHDO-g-PDMAEA well-defined graft copolymers were constructed through the grafting-from technique via SET-LRP of 2-(dimethylamino)ethyl acrylate (DMAEA) in acetone, a nonpolar solvent, initiated by the macroinitiator using CuCl/Me6TREN as catalytic system. The narrow molecular weight distributions (Mw/Mn ≤ 1.18) and kinetics experiment showed the controllability of SET-LRP graft copolymerization of DMAEA. The critical micelle concentrations (cmc) of PMHDO-g-PDMAEA amphiphilic graft copolymers in aqueous solution were determined by fluorescence probe technique and the dependence of cmc on pH or salinity were also investigated. Micellar morphologies were visualized using transmission electron microscopy.

Synthesis of Ethyl Cellulose Grafted Poly(N-isopropylacrylamide) Copolymer and Its Micellization

Thermo-responsive graft copolymers, ethyl cellulose grafting poly(N-isopropylacrylamide) (EC-g-PNIPAm), were synthesized by single-electron transfer living radical polymerization (SET-LRP) in THF/methanol mixed solvent. Ethyl cellulose macro-initiators (EC-Br) for SET-LRP were synthesized by the esterification between the hydroxyl groups on EC backbones and 2-bromoisobutyryl bromides. The degree of substitution of the EC-Br macro-initiator was tailored by varying the feeding mole ratio of 2-bromoisobutyryl bromide to the hydroxyl group on ethyl cellulose. Three EC-Br macro-initiators with different Br substitutions were used as the macro-initiators and it was found that the converting degree of the initiator sites was efficient and the graft density of graft copolymer was controllable. The SET-LRP of NIPAm was efficient that the monomer conversion was above 60% within 25 h. The linear plot of ln((M)0/(M)t) versus the conversion indicated that the reaction was living and controllable. The graft copolymers were characterized by means of gel permeation chromatography (GPC), 1 H NMR and FTIR spectroscopy. GPC peak of the graft copolymer became narrower and shifted to the low elution time with the increase of reactive time. The molecular weight of the side-chain linearly increased with the reaction time. EC-g-PNIPAm copolymers were typical amphiphilic graft copolymers, having the hydrophobic EC backbone and the hydro- philic PNIPAm side chains. They could be self-assembled and form stable micelles in a selective solvent, water. The micelles were in spherical shape with typical diameter around 100 nm. Rod-like and flower shaped particles were also observed, which was probably due to the fusion of the spherical shaped micelles. The structure of the spherical shaped micelles was that the EC backbone collapsed to form the core of the micelles and the hydrophilic PNIPAm chains stayed in the outside of the micelles to stabilize the micelles. Due to the thermoresponsive branch chains of PNIPAm, the micelles could shrink with rising temperature due to the collapses of the PNIPAm side chains. Keywords ethyl cellulose; poly(N-isopropylacrylamide); single-electron transfer living radical polymerization (SET-LRP), graft polymerization; thermoresponsive

Interrupted SET-LRP of methyl acrylate demonstrates Cu(0) colloidal particles as activating species

To determine how “nascent” Cu(0) colloidal nanoparticles mediate the single electron transfer-living radical polymerization (SET-LRP), two different series of interruption experiments were performed on SET-LRP of methyl acrylate in DMSO with [MA]0/[MBP]0/[Me6-TREN]0 = 222/1/0.1 and hydrazine-activated Cu(0) wire. When the polymerization was interrupted by lifting the Cu(0) wire wrapped around the stirring bar out of the reaction medium with a magnet, leaving colloidal Cu(0) particles, soluble CuBr and CuBr2 formed during the reaction in solution, the polymerization still proceeded, but at a much slower rate. However, by carefully decanting the reaction mixture from one Schlenk tube containing the Cu(0) wire catalyst to a second one without the Cu(0) catalyst, the polymerization reached a complete stop. This decantation experiment demonstrates that soluble CuBr/L cannot be a major contributor to the activation process in SET-LRP. Therefore colloidal Cu(0) particles generated from the disproportionation of CuBr/L are the catalytic species. The presence of the Cu(0) colloidal particles in the reaction medium in the direct lifting setup is most likely responsible for the continued polymerization in the absence of the Cu(0) wire catalyst. Furthermore, SET-LRP was demonstrated to be “immortal” towards catalyst removal. Finally, it was demonstrated that colloidal Cu(0) nanoparticles formed via disproportionation agglomerate into highly visible particles that were immediately consumed upon addition of the methyl 2-bromopropionate initiator, leaving no observable Cu(0) aggregates.

Quantitative formation of core cross-linked star polymers via a one-pot two-step single electron transfer-living radical polymerization

A novel and highly efficient one-pot two-step strategy towards core cross-linked star polymers based on single electron transfer-living radical polymerization (SET-LRP) is described. Macroinitiators with high end-group fidelity were generated at high monomer conversions prior to the addition of cross-linkable monomers in the same pot to induce the formation of star polymers. Quantitative (>99%) star formation is achieved without the purification of unreacted monomers or macroinitiators.

Preparation of a novel skeleton weak anion-exchange monolith by single electron transfer-living radical polymerization for protein separation in high performance liquid chromatography

A novel skeleton weak anion-exchange monolith was prepared by single electron transfer-living radical polymerization (SET-LRP) for high performance liquid chromatography (HPLC). In this study, vinyl ester resin was used as the monomer, ethyleneglycol dimethacrylate as the cross linking agent, carbon tetrachloride as the initiator, ferrous powder as the catalyst, and N,N,N′,N′-tetramethylethylenediamine as the ligand to supply amine-groups. The polymerization conditions were optimized. The characters of the monolith were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy and mercury porosimeter, respectively. Good skeleton structure properties were obtained. Moreover, the prepared monolith was used as HPLC stationary phase to separate immune globulin G (IgG) from human plasma with high efficiency. The influences of buffer concentration and pH of the mobile phase on the separation of IgG were investigated. In addition, the monolith was also used to separate the mixture of beef serum albumin (BSA), IgG and lysozyme (Lys) successfully.

SET-LRP of hydrophobic and hydrophilic acrylates in trifluoroethanol

Efficient disproportionation of CuBr–Me6-TREN in 2,2,2-trifluoroethanol (TFE) to produce “nascent” Cu(0) and CuBr2–Me6-TREN indicates that this semifluorinated alcohol has the potential to be an excellent solvent for Cu(0) mediated single electron transfer-living radical polymerization (SET-LRP). Herein, we report the SET-LRP of a range of hydrophobic and hydrophilic acrylates, including methyl acrylate (MA), n-butyl acrylate (nBA), tert-butyl acrylate (tBA), 2-ethylhexyl acrylate (EHA) and 2-hydroxyethyl acrylate (HEA) using 2-bromopropionate (MBP) and 2-ethylbromoisopropionate (EBiB) as initiators, and Me6-TREN as ligand in TFE. Analysis of the kinetics of polymerization and of the polymer chain ends by a combination of 1H NMR, GPC, MALDI-TOF and chain-end functionalization by “thio-bromo” click reaction demonstrated the synthesis of perfect or near-perfect chain-end functional polyacrylates by SET-LRP in TFE.

Synthesis of PMMA by Single-Electron Transfer Radical Polymerization Using Benzyl Chloride as Initiator

Single electron transfer living radical polymerization (SET-LRP) has developed to be a robust tool for the construction of well-designed polymers. This paper reports the influence of one cheaper initiator on the SET-LRP process. The SET-LRP of methyl methacrylate (MMA) initiated with benzyl chloride and catalyzed by Cu(0)/PMDETA at 25°C in methanol is described. The polymerization kinetics was recorded. The reactions followed first-order kinetic in monomer consumption and the molecular weights increased linearly with conversion while retaining narrow molecular weight distribution. Therefore, it is plausible that SET-LRP of MMA initiated with benzyl chloride process to yield well defined macromolecules.