Atom Transfer Radical Polymerization Of Methyl Acrylate Research Articles

Tripodal heptadentate amine ligands with different nitrogen substituents for SARA- and photo-ATRP

Tripodal heptadentate amine ligands, tris[N-(2-pyridylmethyl)-2-aminoethyl]amine (Py3H3Tren) and tris[N-(2-pyridylmethyl)-N-methyl-2-aminoethyl]amine (Py3Me3Tren), are used as the active ligands for atom transfer radical polymerization (ATRP). Both of them evolve from a Schiff base ligand, tris[N-(2-pyridylmethyl)-2-iminoethyl]amine (Py3Tren), through simple reduction and methylation reactions. Electrospray ionization mass spectrometry is used to investigate the coordination between the ligands and CuBr2 at an equimolar amount in the solution. It reveals that CuBr2/Py3H3Tren and CuBr2/Py3Me3Tren are tripod claw-shaped complexes. Electrochemical studies show that CuBr2/Py3H3Tren has a more negative redox potential and higher reactivity than the other two counterparts. The order of KATRP of CuBr2/ligand is Py3H3Tren > Py3Me3Tren > Py3Tren. Subsequently, CuBr2/Py3H3Tren and CuBr2/Py3Me3Tren are employed as the catalysts for the supplemental activators and reducing agents (SARA) ATRP of methyl acrylate (MA). Well-defined poly(MA) with controlled molecular weight and low Mw/Mn could be synthesized with the almost quantitative monomer conversion at room temperature, and CuBr2/Py3Me3Tren has the fastest reaction rate. Photo-induced atom transfer radical polymerization (Photo-ATRP) of MA using Py3H3Tren and Py3Me3Tren as the ligand are also performed. Photo-ATRP using Py3H3Tren has the fastest reaction rate, while the polymerizations using Py3Me3Tren has shown lower polydispersity.

ATRP of Methyl Acrylate by Continuous Feeding of Activators Giving Polymers with Predictable End-Group Fidelity.

Atom transfer radical polymerization (ATRP) of methyl acrylate (MA) was carried out by continuous feeding of Cu(I) activators. Typically, the solvent, the monomer, the initiator, and the CuBr2/Me6TREN deactivator are placed in a Schlenk flask (Me6TREN: tris[2-(dimethylamino)ethyl]amine), while the CuBr/Me6TREN activator is placed in a gas-tight syringe and added to the reaction mixture at a constant addition rate by using a syringe pump. As expected, the polymerization started when Cu(I) was added and stopped when the addition was completed, and polymers with a narrow molecular weight distribution were obtained. The polymerization rate could be easily adjusted by changing the activator feeding rate. More importantly, the loss of chain end-groups could be precisely predicted since each loss of Br from the chain end resulted in the irreversible oxidation of one Cu(I) to Cu(II). The Cu(I) added to the reaction system may undergo many oxidation/reduction cycles in ATRP equilibrium, but would finally be oxidized to Cu(II) irreversibly. Thus, the loss of chain end-groups simply equals the total amount of Cu(I) added. This technique provides a neat way to synthesize functional polymers with known end-group fidelity.

CuBr/PMDETA combined with triethanolamine as an economic and highly active catalyst for atom transfer radical polymerization

ABSTRACTCuBr ligated with N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) is a common catalyst for atom transfer radical polymerization (ATRP). A catalyst/initiator ratio of 0.5–1 is generally required for most CuBr/PMDETA-catalyzed polymerizations, leading to high catalyst loading and high cost of post-polymerization purification. In this work, triethanolamine is found to drastically improve the catalytical performance of CuBr/PMDETA and the strong promotion effects of triethanolamine on ATRP of methyl acrylate (MA), methyl methacrylate (MMA) and styrene (St) have been investigated. In the presence of triethanolamine, the catalyst loading of CuBr/PMDETA is substantially reduced from a normal catalyst/initiator ratio of 1 to 0.01, 0.05 and 0.05 respectively in the polymerization of MA, MMA and St. As CuBr/PMDETA is one of the cheapest ATRP catalysts, the combination of CuBr/PMDETA with triethanolamine further markedly decreases the catalyst consumption and reduces the cost of post-purification for ATRP at large scales, and therefore is promising for potential industrial applications.

Atom Transfer Radical Polymerization with Different Halides (F, Cl, Br, and I): Is the Process “Living” in the Presence of Fluorinated Initiators?

Atom transfer radical polymerization (ATRP) is often used for grafting from fluorinated polymers. Nevertheless, the possibility to initiate an ATRP from a C–F functionality and the activity of the catalysts in the presence of fluoride anions are essentially unexplored. Therefore, we investigated the thermodynamics and kinetics of C–F bond activation by ATRP catalysts and compared it with other halide systems. The ATRP equilibrium constant was estimated to be small for the reaction between [CuITPMA]+ and benzyl fluoride (TPMA = tris(2-pyridylmethyl)amine). However, [CuITPMA]+ could react with the more active initiator diethyl fluoromalonate (DEFM). With DEFM as initiator and CuIBr/TPMA as catalyst, ATRP of methyl acrylate and styrene displayed initiation efficiencies of 73% and 95%, respectively. ATRP deactivation by [F–CuIITPMA]+ was slow and followed by even slower activation of newly formed C–F bonds, leading to limited conversion. Comparison with other halides indicates that Br- and Cl-based ATRP syste...

Synthesis of well-defined 3-arm and 6-arm poly(acrylic acid)s via ATRP of methyl acrylate and hydrolyses of 3-arm and 6-arm poly(methyl acrylate)s

Three-arm and 6-arm poly(methyl acrylate)s (PMAs) were synthesized via atom transfer radical polymerization (ATRP) with 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene and hexakis(bromomethyl)benzene as the initiators, CuBr as the catalyst and tris [2-(dimethylamino) ethyl] amine (Me6TREN) as the ligand. The effect of the molar ratio of CuBr and Me6TREN to Br of the initiator on the arm number was investigated. Hydrolysis of the products was conducted to convert the PMAs to poly(acrylic acid)s (PAAs). The solubility to water and thermal decomposition curves of 3-arm and 6-arm PAAs corresponded well to those of PAA.

Inorganic Sulfites: Efficient Reducing Agents and Supplemental Activators for Atom Transfer Radical Polymerization.

Inorganic sulfites such as sodium dithionite (Na2S2O4), sodium metabisulfite (Na2S2O5), and sodium bisulfite (NaHSO3) have been studied as reducing agents for atom transfer radical polymerization (ATRP). They act not only as very efficient reducing agents but also as supplemental activators for SARA (supplemental activator and reducing agent) ATRP of methyl acrylate in DMSO at ambient temperature. In combination with Cu(II)Br2/Me6TREN, they produced poly(methyl acrylate) with controlled molecular weight, low dispersity (Mw/Mn = 1.05), and well-defined chain-end functionality. Sulfites are eco-friendly, approved by FDA as food and beverage additives, and used commercially in many industrial processes.

Effect of crosslinker multiplicity on the gel point in ATRP

AbstractThe experimental gelation was studied in atom transfer radical polymerization (ATRP) of methyl acrylate (MA) with various branching reagents that structurally differ by the number of vinyl groups (multiplicity). MA was copolymerized with branching reagents containing 2, 3, 4, 5, or 6 acrylate moieties per molecule, respectively. Reactions with a constant concentration of branching vinyl groups (the same molar ratio of [Vinylbranch]0/[Initiator]0) revealed a different gelation behavior when ethylene glycol diacrylate (2A) and trimethylolpropane triacrylate (3A) were used as crosslinkers, whereas the reactions using pentaerythritol tetraacrylate (4A) showed similar gelation behavior as compared to reactions using 3A. Additional reactions with dipentaerythritol pentaacrylate (5A) and hexafunctional acrylate crosslinkers (6A) revealed the presence of a concentration‐dependant gelation behavior. On the other hand, in reactions with the same molar concentration of various crosslinkers, gelation occurred at progressively lower MA conversions for reactions with an increasing number of vinyl groups per crosslinker. In addition, the number of unreacted pendant vinyl groups in the sols was compared for reactions with different multiplicity of the crosslinker and various ratios of [Vinylbranch]0/[Initiator]0. Finally, a linear oligomeric crosslinker containing multiple branching vinyl groups along the side chain was used as the branching reagent for gelation. The gelation behavior during the ATRP of MA with the linear crosslinker was different as compared to the use of the aforementioned crosslinkers with a star‐like architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2016–2023, 2010

An Efficient Route to Cyclic Polymers by ATRP–RCM Process

Abstract An efficient synthetic route to cyclic polymers has been demonstrated through atom-transfer radical polymerization (ATRP) and subsequent ring-closing metathesis (RCM) reaction. Thus, telechelic poly(methyl acrylate) (PMA) having allyl groups was synthesized by ATRP of methyl acrylate with a difunctional initiator and the subsequent end-capping reaction with allyltributyltin. The following RCM reaction proceeded even under dilution in the presence of the Grubbs catalyst to give a cyclic PMA in a high yield.

Poly(acrylate‐b‐styrene‐b‐isobutylene‐b‐styrene‐b‐acrylate) Block Copolymers via Carbocationic and Atom Transfer Radical Polymerizations

A series of polyacrylate‐polystyrene‐polyisobutylene‐polystyrene‐polyacrylate (X‐PS‐PIB‐PS‐X) pentablock terpolymers (X=poly(methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly(methyl methacrylate) (PMMA)) was prepared from poly (styrene‐b‐isobutylene‐b‐styrene) (PS‐PIB‐PS) block copolymers (BCPs) using either a Cu(I)Cl/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) or Cu(I)Cl/tris[2‐(dimethylamino)ethyl]amine (Me6TREN) catalyst system. The PS‐PIB‐PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization (ATRP) of methyl acrylate (MA), n‐butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu(I)Cl/PMDETA or Cu(I)Cl/Me6TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. 1H‐NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS‐PIB‐PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.

Star polymers by ATRP of styrene and acrylates employing multifunctional initiators

AbstractMultifunctional initiators for atom transfer radical polymerization (ATRP) are prepared by converting ditrimethylolpropane with four hydroxyl groups, dipentaerythritol with six hydroxyl groups, and poly(3‐ethyl‐3‐hydroxymethyl‐oxetane) with ∼11 hydroxyl groups to the corresponding 2‐bromoisobutyrates or 2‐bromopropionates as obtained by reaction with acid bromides. Star polystyrene (PS) is produced by using these macroinitiators and neat styrene in a controlled manner by ATRP at 110 °C, employing the catalytic system CuBr and bipyridine. Mn up to 51,000 associated with narrow molecular weight distributions (PDI < 1.1) are obtained with conversions up to 32%. Hydrolysis of the star‐PS leads to linear chains having the expected Mn values. The star‐PS polymers based on dipentaerythritol degrade thermally in nitrogen in a two‐step process in which the first low‐temperature step involves scission of the ester linkages and the second step corresponds to the normal PS degradation. Star poly(methyl acrylates) with various cores are likewise prepared in a controlled manner by ATRP of methyl acrylate in bulk and in solution at 60–80 °C with the 1,1,4,7,7‐pentamethyldiethylene triamine ligand. Under these conditions, higher conversions were possible still maintaining low PDI signaling controlled star growth. Multiarm stars of poly(n‐butyl acrylate) and poly(n‐hexyl acrylate) with controlled characteristics have also been prepared. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3748–3759, 2005

EPR and Kinetic Studies of Atom Transfer Radical Polymerization of (Meth)acrylates

Electron paramagnetic resonance (EPR) spectroscopy and kinetic analysis were applied to atom transfer radical polymerization (ATRP) of (meth)acrylates. Although only copper(I) species was added to the system initially, EPR signals of copper(II) species were clearly observed in the polymerization mixture of methyl methacrylate (MMA) initiated by either ethyl 2-bromoisobutyrate (EBB) or p-toluenesulfonyl chloride (TsCl) in diphenyl ether. ATRP of methyl acrylate (MA) initiated by methyl 2-bromopropionate (MBP) in diphenyl ether also showed clear EPR signal of copper(II) species. As the polymerization proceeded, the concentration of copper(II) increased gradually until a nearly steady state was reached. The correlation between time dependence of concentration of copper(II) species and kinetics of polymerization is discussed for various ATRP systems. Our results indicate that conversion of 5—6% of initial copper(I) species to copper(II) species is observed for polymerization of MMA at 90°C and ca. 30% conversion was found for MA.