Ethyl 2-bromoisobutyrate Research Articles

Cyclometalated Ruthenium(II) Complex as a Versatile Catalyst for Living/Controlled Radical Polymerization of Hydrophobic and Hydrophilic Monomers

AbstractCyclometalated complex, cis‐[Ru(phpy)(phen)(MeCN)2]PF6, bearing strongly bound ligands (phpy = 2‐phenylpyridine, phen = 1, 10‐ phenantroline) and relatively labile (MeCN) ligands, in conjunction with ethyl 2‐bromoisobutyrate (EBiB), was used for radical polymerization of three hydrophobic, styrene (St), methyl methacrylate (MMA), n‐butyl acrylate (BA), and one hydrophilic, 2‐hydroxyethyl methacrylate (HEMA), monomers. The polymerizations were fast and reasonably controlled; the molecular weights increased with conversion and were close to the calculated values. The best control was achieved in polymerization of St. The complex was able to mediate this polymerization with acceptable rate and level of control even at a monomer/catalyst ratio of 2000. The living character of the polymerizations was confirmed by chain extension experiments; the degree of polymer “livingness” was less for PMMA than for PSt. Because of ionic nature, the complex was well soluble in MeOH and thus catalyzed polymerization of HEMA under homogeneous conditions at 50 °C.

Iron-mediated (dual) concurrent ATRP–RAFT polymerization of water-soluble poly(ethylene glycol) monomethyl ether methacrylate

In this work, the iron-mediated (dual) concurrent ATRP–RAFT polymerization of water-soluble poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) was investigated at different polymerization temperatures (from 90 °C to 30 °C), using 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) as an alkyl pseudohalide initiator, ethyl 2-bromoisobutyrate (EBiB) as a co-initiator, and FeCl3·6H2O/PPh3 complex as the catalyst. The polymerization kinetics was studied in detail at polymerization temperatures of 90 °C and 30 °C. The results showed that the concurrent ATRP–RAFT polymerization (using only CPDN as the initiator) of PEGMA could be carried out successfully, even if the polymerization temperature was reduced to 30 °C. Furthermore, the polymerization rate was remarkably enhanced via dual concurrent ATRP–RAFT polymerization (using CPDN and EBiB as co-initiators). For example, the monomer conversion could be higher than 70% in the dual concurrent ATRP–RAFT polymerization system in 65.5 h, while a conversion of only 22% could be obtained after 167 h for the concurrent ATRP–RAFT polymerization system at 30 °C. The “living” features of dual concurrent ATRP–RAFT polymerization of PEGMA were verified by chain end analysis and chain-extension experiments.

SET-LRP of 2-hydroxyethyl acrylate in protic and dipolar aprotic solvents

Cu(0) wire-mediated single-electron transfer living radical polymerization (SET-LRP) of 2-hydroxyethyl acrylate (HEA) was performed in protic solvents, MeOH, binary mixtures of MeOH and EtOH with H2O, and H2O, and in the dipolar aprotic solvent, DMSO. The tertiary alkyl halide initiator, ethyl 2-bromoisobutyrate (EBiB), and the tris[2-(dimethylamino)ethyl]amine (Me6-TREN) ligand mediated rapid SET-LRP of HEA providing poly(HEA) (PHEA) with narrow Mw/Mn. When SET-LRP of HEA was performed at high H2O content in MeOH, and in H2O, gel formation was observed exclusively on the Cu(0) wire surface. This demonstrated the heterogeneous nature of the Cu(0)-mediated SET activation that promotes a strong adsorption of PHEA and slow diffusion of PHEA radicals generated from activation on the Cu(0) wire surface by the hydrophobic effect. High molecular weight PHEA was obtained at [M]0/[I]0 = 400 and 800 with Mw/Mn < 1.45 in MeOH + 40% H2O in 50 min. This suggests significantly less termination and a much higher rate of SET-LRP of HEA at 25 °C than in the previously reported CuX-catalyzed polymerization of HEA in bulk (90% conversion, Mn = 30 000 after 14 h at 90 °C) or solution (87% conversion, Mn = 14 700 after 12 h at 90 °C) at elevated temperatures. When targeting higher [M]0/[I]0, Mw/Mn increases with conversion but first order kinetics was observed. This was attributed to the increased hydrophobic effect of PHEA at higher Mn that is accompanied by slow desorption of the polymer from the Cu(0) wire and a reduced exchange rate between dormant and active species.

Effect of cholesterol-poly(N,N-dimethylaminoethyl methacrylate) on the properties of stimuli-responsive polymer liposome complexes

The development of new polymer–liposome complexes (PLCs) as delivery systems is the key issue of this work. Three main areas are dealt with: polymer synthesis/characterization, liposome formulation/characterization and evaluation of the PLCs uptake by eukaryotic cells.Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with low molecular weight and narrow polydispersity was synthesized by Atom Transfer Radical Polymerization (ATRP). The polymers were synthesized using two different bromide initiators (cholesteryl-2-bromoisobutyrate and ethyl 2-bromoisobutyrate) as a route to afford PDMAEMA and CHO-PDMAEMA.Both synthesized polymers (PDMAEMA and CHO-PDMAEMA) were incorporated in the preparation of lecithin liposomes (LEC) to obtain PLCs. Three polymer/lipid ratios were investigated: 5, 10 and 20%. Physicochemical characterization of PLCs was carried out by determining the zeta potential, particle size distribution, and the release of fluorescent dyes (carboxyfluorescein CF and calcein) at different temperatures and pHs.The leakage experiments showed that CHO covalently bound to PDMAEMA strongly stabilizes PLCs. The incorporation of 5% CHO-PDMAEMA to LEC (LEC_CHO-PD5) appeared to be the stablest preparation at pH 7.0 and at 37°C. LEC_CHO-PD5 destabilized upon slight changes in pH and temperature, supporting the potential use of CHO-PDMAEMA incorporated to lecithin liposomes (LEC_CHO-PDs) as stimuli-responsive systems.In vitro studies on Raw 264.7 and Caco-2/TC7 cells demonstrated an efficient incorporation of PLCs into the cells. No toxicity of the prepared PLCs was observed according to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. These results substantiate the efficiency of CHO-PDMAEMA incorporated onto LEC to assist for the release of the liposome content in mildly acidic environments, like those found in early endosomes where pH is slightly lower than the physiologic.In summary, the main achievements of this work are: (a) novel synthesis of CHO-PDMAEMA by ATRP, (b) stabilization of LEC by incorporation of CHO-PDMAEMA at neutral pH and destabilization upon slight changes of pH, (c) efficient uptake of LEC_CHO-PDs by phagocytic and non-phagocytic eukaryotic cells.

Effect of storage conditions on MMA polymerization via Fe(III)-mediated ATRP without any reducing agent

In a variety of storage conditions, Fe(III)-mediated polymerization of methyl methacrylate (MMA) uses FeX3 (X=Cl & Br), diphenyl-2-pyridylphosphine (DPPP) ligand and ethyl-2-bromoisobutyrate (EBriB) as an initiator at 80 °C in toluene without using any external reducing agents. The FeCl3 and FeBr3 containing 980 and 1,890 ppm of water during outside storage for 2 and 4 days, respectively, were successfully used for MMA polymerization through atom transfer radical polymerization (ATRP) without using any reducing agent. Moisture content of the polymerization system increases as the period of outside storage increases. It turned out that most of the polymerizations were under control even after keeping metal salts and their complexes outdoors for 4 days exhibiting a polydispersity less than 1.5. The kinetic plot between ln [M]0/[M] and time demonstrated linearity during the polymerization. A chain extension study clearly reveals that the moisture contaminated FeX3 due to outdoor storage, is able to catalyze the ATRP of MMA in the absence of any additive by a living radical mechanism. Open image in new window

Iron‐mediated AGET ATRP of MMA with sulfosalicylic acid as a ligand

AbstractIron‐mediated atom transfer radical polymerizations with activators generated by electron transfer of methyl methacrylate in N,N‐dimethylformamide solution in the presence and absence of a limited amount of air, using FeCl3·6H2O as the catalyst, ethyl 2‐bromoisobutyrate (EBiB) as the initiator, vitamin C as the reducing agent, and a commercially available organic acid, sulfosalicylic acid (SSA), as the ligand were investigated. Addition of SSA as the ligand could enhance the polymerization rate, and produce poly(methyl methacrylate) with controllable molecular weights and narrow molecular weight distributions (Mw/Mn = 1.30–1.50). The effect of [FeCl3·6H2O]0/[SSA]0 on the polymerization was studied by cyclic voltammetry characterization. Chain extension was performed to confirm the “living”/controlled nature of the polymerization system. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Iron-mediated AGET ATRP of MMA using acidic/basic salts as reducing agents

In this study, iron-mediated activator generated by electron transfer for atom transfer radical polymerization of methyl methacrylate was carried out using two different types of salts, acidic hydroxylamine hydrochloride and basic sodium bisulfite as the reducing agents, ethyl 2-bromoisobutyrate as an initiator, FeCl3·6H2O as a catalyst and triphenylphosphine (PPh3) as a ligand. The polymerization could be carried out in the presence of a limited amount of oxygen (air) and showed highly efficient catalyst activity. The living features were confirmed by the polymerization kinetics, analysis of chain end, and chain-extension experiment.

Comproportionation versus Disproportionation in the Initiation Step of Cu(0)-Mediated Living Radical Polymerization

We present a study of the initiation step in copper(0)-mediated atom transfer radical polymerization (also known as SET-LRP or SARA ATRP), in which a nitroxide free radical, N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (SG1), is used to trap radicals derived from ethyl 2-bromoisobutyrate (EBiB), copper metal and pentamethyl diethylene triamine (PMDETA) ligand. A kinetic model was developed relating the rate of conversion of EBiB to the rate constants of activation by copper metal (ka0) and comproportionation of Cu0 and CuII (kcomp). This allowed the determination of these parameters in several solvents, including dimethyl sulfoxide (DMSO), dimethylformamide (DMF), ethanol (EtOH), and acetonitrile (MeCN), in which significant levels of comproportionation were observed, leading to autoacceleration of the reaction. A similar treatment of copper-mediated polymerization kinetics predicts 1/2 order dependence on initiator concentration and copper surface area, in accordance with previously...

Enhanced Activity of ATRP Fe Catalysts with Phosphines Containing Electron Donating Groups

Fe-based atom transfer radical polymerization (ATRP) of styrene (St) with various triarylphosphines containing electron donating methoxy groups was investigated. FeIIIBr3 in the presence of tris(2,4,6- trimethoxyphenyl)phosphine (TTMPP) provided faster ATRP of St than in the presence of tris(4-methoxyphenyl)phosphine (TMPP) and much faster than with triphenylphosphine (TPP) under identical conditions. ATRP of St was carried out with initial ratio of reagents: [St]:[EBiB]:[FeIIIBr3]:[TTMPP] = 200:1:1:2, in 50% (v/v) anisole at 100 °C (EBiB is ethyl 2-bromoisobutyrate). After 21 h, conversion reached 92%, yielding polystyrene with molecular weight Mn = 24 100 and Mw/Mn = 1.25. With TMPP and TPP under the same conditions, the conversion of monomer was only 19% and 9%, respectively. With 1 equiv of TTMPP vs FeIIIBr3, control was better, Mw/Mn ∼ 1.1, but polymerization was slower. The phosphines could directly reduce FeIII to FeII but could also act as ligands complexing transition metal and forming efficient ...

Synthesis of amphiphilic A2B star-shaped copolymers of polystyrene-b-[poly(ethylene oxide)]2 via atom transfer nitroxide radical coupling

The amphiphilic A2B star-shaped copolymers of polystyrene-b-[poly(ethylene oxide)]2 (PS-b-PEO2) were synthesized via the combination of atom transfer nitroxide radical coupling (ATNRC) with ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) mechanisms. First, a novel V-shaped 2,2,6,6-tetramethylpiperidine-1-oxyl-PEO2 (TEMPO-PEO2) with a TEMPO group at middle chain was obtained by ROP of ethylene oxdie monomers using 4-(2,3-dihydroxypropoxy)-TEMPO and diphenylmethyl potassium as coinitiator. Then, the linear PS with a bromine end group (PS-Br) was obtained by ATRP of styrene monomers using ethyl 2-bromoisobutyrate as initiator. Finally, the copolymers of PS-b-PEO2 were obtained by ATNRC between the TEMPO and bromide groups on TEMPO-PEO2 and PS-Br, respectively. The structures of target copolymers and their precursors were all well-defined by gel permeation chromatographic and nuclear magnetic resonance (1H NMR). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Iron‐mediated AGET ATRP of methyl methacrylate using metal wire as reducing agent

AbstractMethyl methacrylate (MMA) were successfully polymerized by atom transfer radical polymerization with activator generated by electron transfer (AGET ATRP) using copper or iron wire as the reducing agent at 90°C. Well‐controlled polymerizations were demonstrated using an oxidatively stable iron(III) chloride hexahydrate (FeCl3·6H2O) as the catalyst, ethyl 2‐bromoisobutyrate (EBiB) as the initiator, and tetrabutylammonium bromide (TBABr) or triphenylphosphine as the ligand. The polymerization rate was fast and affected by the amount of catalyst and type of reducing agents. For example, the polymerization rate of bulk AGET ATRP with a molar ratio of [MMA]0/[EBiB]0/[FeCl3·6H2O]0/[TBABr]0 = 500/1/0.5/1 using iron wire (the conversion reaches up to 82.2% after 80 min) as the reducing agent was faster than that using copper wire (the conversion reaches up to 86.1% after 3 h). At the same time, the experimental Mn values of the obtained poly(methyl methacrylate) were consistent with the corresponding theoretical ones, and the Mw/Mn values were narrow (∼1.3), showing the typical features of “living”/controlled radical polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Diblock fluoroacrylate copolymers from two initiators: synthesis, self-assembly and surface properties

Diblock fluoroacrylate copolymers poly(methyl methacrylate) (PMMA)-b-poly(dodecafluoroheptyl methacrylate) (PMMA-b-PDFHM) for coating materials are synthesized via atom transfer radical polymerization (ATRP) by two different initiators, a brominated initiator end group terminated by 1H,1H,2H,2H-heptadecafluoro (F–Br) and the conventional initiator ethyl 2-bromoisobutyrate (EBiB). The copolymer structures are characterized by 1H NMR, 19F NMR and GPC analyses. The influence of the two initiators on the self-assembly behavior and the surface properties of PMMA-b-PDFHM films are explored. Because of the divergent solubility of the segments in chloroform (CHCl3), tetrahydrofuran (THF) and trifluorotoluene (TFT) solutions, the self-assembly of PMMA-b-PDFHM in CHCl3, THF and TFT was investigated using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Accordingly, the properties of PMMA-b-PDFHM films cast from CHCl3, THF and TFT solutions were compared for their surface wettability, surface free energy, surface elemental composition, surface morphology and roughness, and surface water adsorption, through analysis of static contact angle (SCA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and quartz crystal microbalance with dissipation (QCM-D). It is found that the copolymers F-PMMA-b-PDFHM using F–Br initiator and E-PMMA-b-PDFHM using EBIB initiator, reveal both unimers (7–9 nm) and micelles (220–360 nm) in THF and CHCl3 solutions, which are recognized by TEM as dichroic half-spherical or core–shell particles, but occur mainly as unimers (5–9 nm) in TFT solution, which is favorable for obtaining films with low surface free energies. F-PMMA-b-PDFHM films show lower surface free energy (17.1–17.7 mN m−1) than E-PMMA-b-PDFHM films (17.9–22.9 mN m−1) in each solvent. The surface morphology and roughness determined are strongly controlled by the cast solutions. F-PMMA-b-PDFHM films exhibit a low wettability and high stable surface due to a well-ordered fluorocarbon surface provided by both PDFHM and F–Br groups, and therefore can be developed into a high-performance coating material.

AGET ATRP of methyl methacrylatevia a bimetallic catalyst

In this work, atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of methyl methacrylate (MMA) using a novel bimetallic catalyst system based on FeCl3·6H2O/CuCl using tris(3,6-dioxaheptyl)amine (TDA-1) or triphenylphosphine (PPh3) as ligand was carried out in bulk at 90 °C for the first time. The kinetics of the polymerizations with a molar ratio of [MMA]0/[ethyl 2-bromoisobutyrate (EBiB)]0/[FeCl3·6H2O]0/[TDA-1 or PPh3]0/[CuCl]0 = 300 : 1 : 0.5 : 1.5 : 0.1 were studied. At the same time, different reference experiments for the mono-metallic catalyst system (i.e., MMA/EBiB/FeCl3·6H2O/TDA-1 or PPh3/ascorbic acid, MMA/EBiB/FeCl3·6H2O/TDA-1 or PPh3, MMA/EBiB/FeCl2·4H2O/TDA-1 or PPh3, MMA/EBiB/CuCl/TDA-1 or PPh3) were also investigated. By comparison to these mono-metallic catalyst systems, both the polymerization rate and controllability over molecular weight and molecular weight distribution were enhanced for the bimetallic catalyst system. The nature of “living”/controlled free radical polymerization under bimetallic catalyst system was confirmed by chain extension experiments.

Copolymerization of Styrene and Methyl Methacrylate Mediated by Copper (0)/2,2′-Bipyridine in the Presence and Absence of Phenol

In this work, we reported the synthesis of random copolymers of P(MMA-co-styrene) via single electron transfer-living radical polymerization (SET LRP) using ethyl 2-bromoisobutyrate and Cu(0)/2,2′-bipyridine as initiator and catalyst combination, respectively. The polymerization took place in the presence of phenol at 25°C. The kinetics results showed that the copolymerization is first order kinetics. The molecular weights increased linearly with the increasing of monomer conversion with a narrow polydispersity index, and the copolymerization rate increased in the presence of phenol. In additional, solvent also has a profound effect on the polymerization. The chain extension experiment demonstrated that the copolymerization exhibited a characteristic of living. The obtained random copolymer was characterized by FTIR, 1H-NMR and GPC.

N‐(n‐Alkyl)‐2‐pyridinemethanimine mediated atom transfer radical polymerization of lauryl methacrylate: Effect of length of alkyl group

AbstractThe article describes the polymerization of lauryl methacrylate (LMA) using Cu(I)Br as catalyst for atom transfer radical polymerization in conjunction with N‐(n‐propyl) [PPMI]/(n‐hexyl) [HPMI]/(n‐octyl) [OPMI]‐2‐pyridinemethanimine as complex ligands. The polymerization of LMA was investigated in bulk and solution (toluene as solvent) using Cu(I)Br as catalyst, N‐(n‐alkyl)‐2‐pyridinemethanimine as ligands and ethyl‐2‐bromo isobutyrate (EBiB) as initiator. The ratio of LMA : CuBr : Ligand : EBiB was kept constant in all the polymerizations. In bulk polymerization, the solubility of the catalyst complex increased with increasing the length of alkyl chain on the ligand from propyl to octyl and also gave polymers with narrow molecular weight distribution. The PDI was further narrowed by using OPMI as ligand and toluene was used as solvent. The kinetics of polymerization was also analyzed and it clearly shows that % conversion increased with time. Increase in molecular weight with % conversion without affecting PDI clearly show that the system is living and living nature can be controlled by increasing the length of alkyl group. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effects of dual initiators and catalytic additives on atom transfer radical polymerization of styrene

The effect of two initiators, so-called dual initiators system on atom radical transfer polymerization (ATRP), were studied with dimethyl-2,6-dibromohepanedioate (DMDBHD) and ethyl-2-bromoisobutyrate (EBIB). Cu(I)Br as catalyst and N,N,N′,N′,N′-pentamethyl-diethylenetriamine as ligand were employed for styrene ATRP. Interestingly, bimodal MWD were shown for the dual initiator system, and one of the peaks had higher molecular weight (MW) and the other had lower MW compared to a one-initiator system. The lower MW peak in bimodal peaks seemed to be mainly resulting from EBIB and the higher MW peak from DMDBHD. Furthermore, methylaluminoxane (MAO) was fed into the ATRP reaction to observe the effect of it on ATRP. As the MAO/CuBr molar ratio in feed increased from 0 to 1, the molecular weight and conversion increased without a notable change in PDI and curve shape of GPC. The conversion in the presence of MAO was also increased with the increase in MAO/CuBr molar ratio. The effect of Cp*TiCl3 on the ATRP was opposite to that of MAO. As the Cp*TiCl3/CuBr molar ratio increased from 0 to 1, the conversion of polymerization was down from 56 to 35%. Furthermore, the molecular weight was drastically decreased from 10,000 to 5,500, but their PDI did not show a significant change. These results can elucidated by the retarding effect of Cp*TiCl3 on the propagation of polymerization.

Low-Temperature AGET ATRP of Methyl Methacrylate in Ionic Liquid-Based Microemulsions

Sustainable atom transfer radical polymerization of methyl methacrylate (MMA) with activators generated by electron transfer (AGET ATRP) was done using microemulsion polymerization at the relatively low temperature of 30 °C. Ethyl 2-bromoisobutyrate (EBiB) was used as ATRP initiator, ascorbic acid (AA) was used as reducing agent, and CuCl2/N-bis(2-pyridylmethyl)octylamine (BPMOA) was used as catalyst. Microemulsion AGET ATRP of MMA was well-controlled, producing poly(methyl methacrylate) (PMMA) nanoparticles ∼5 nm in diameter and narrow molecular weight distributions (Mw/Mn = 1.20–1.40). After the polymerization and isolation of PMMA, the mixture containing catalysts and ILs was shown to be recoverable and recyclable. Upon replenishment of initiator, reducing agent, and monomer (MMA), AGET ATRP of MMA produced PMMA with reproducible molecular weights and narrow molecular weight distributions, even in the fifth cycle. Thus, this process was demonstrated as being sustainable. Furthermore, use of a new surfa...

The Atom Transfer Radical Polymerization of Methyl Methacrylate in Ionic Liquid Media of 1-Methylimidazolium Alkyltes

Abstract Three brønsted acidic ionic liquids, 1-methylimidazolium acetate ([Hmim][CH3COO]), 1-methylimidazolium propionate ([Hmim][CH3CH2COO]) and 1-methylimidazolium butyrate ([Hmim][CH3CH2CH2COO]) were used as reaction medium for atom transfer radical polymerization of methyl methacrylate with ethyl 2-bromoisobutyrate (EBiB)/CuBr as the initiating system. Kinetic studies, chain extension and block copolymerization confirmed the well-controlled manner of these polymerizations in three brønsted acidic ionic liquids. The reactions were fast and the polydispersities of the polymers were quite narrow (1.10&amp;lt;Mw/Mn&amp;lt;1.34). The rate of polymerization in [Hmim][RCOO] decreased with the increasing alkyl chain lengths (n from 1 to 3), indicating a strong dependence of reaction rate on the length of the substituted groups of the anions in ionic liquids.

Rate-enhanced ATRP in the presence of catalytic amounts of base: An example of iron-mediated AGET ATRP of MMA

The catalytic amount of inorganic bases (i.e., NaOH, Na3PO4, NaHCO3, and Na2CO3) and organic bases such as pyridine and triethylamine was used as the additives in an iron-mediated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of a polar monomer methyl methacrylate (MMA) using FeCl3·6H2O as the catalyst, ethyl 2-bromoisobutyrate (EBiB) as the initiator, ascorbic acid (AsAc) as the reducing agent, and tetrabutylammonium bromide (TBABr) as the ligand. All these bases can result in dual enhancement of polymerization rate and controllability over molecular weight while keeping low Mw/Mn values (<1.3) for the resultant polymers. For example, the polymerization rate of AGET ATRP with a molar ratio of [MMA]0/[EBiB]0/[FeCl3·6H2O]0/[TBABr]0/[AsAc]0/[NaOH]0 = 500/1/1/2/2/1.5 using NaOH as the additives was more than two times of that without NaOH. The nature of “living”/controlled free radical polymerization in the presence of base was confirmed by chain-extension experiments. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Copper-mediated ATRP of MMA in DMSO from unprotected dextran macroinitiators

To easily perform atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in homogeneous medium from unprotected polysaccharidic macroinitiators, the ATRP of MMA carried out in dimethylsulfoxide has been firstly reinvestigated using Cu(I)Br as metal catalyst and ethyl 2-bromoisobutyrate as initiator. Two ligands, 2,2′-bipyridyne (Bpy) and N-(n-propyl)-2-pyridylmethanimine (n-Pr-PMI), have been compared, as well as the addition of Cu(II)Br2 (10 molar % relative to Cu(I)Br) or the adjustment of experimental temperature (from 30 to 60 °C). Appropriate conditions were founded for both ligands to achieve a controlled ATRP. Bpy giving far much faster polymerization compared to n-Pr-PMI, n-Pr-MI was preferred as ligand for accurate tuning of the conversion. Experimental procedure was then applied to unprotected macroinitiators based on dextran to obtain amphiphilic poly(methyl methacrylate) grafted dextran. While homopolymerization was controlled in these conditions, parameters have to be adjusted for the hydrophilic unprotected macroinitiators to prevent gel formation and control ATRP.