Synthesis of polyacrylonitrile via reverse atom transfer radical polymerization catalyzed by FeCl3/isophthalic acid

FeCl₃ coordinated by isophthalic acid was first used as a catalyst in the azobisisobutyronitrile‐initiated reverse atom transfer radical polymerization of acrylonitrile. N,N‐Dimethylformamide was used as a solvent to improve the solubility of the ligand. An FeCl₃‐to‐isophthalic acid ratio of 0.5 not only gave the best control of the molecular weight and its distribution but also provided rather a rapid reaction rate. The effects of different solvents on the polymerization of acrylonitrile were also investigated. The rate of the polymerization in N,N‐dimethylformamide was faster than that in propylene carbonate and toluene. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in N,N‐dimethylformamide. The rate of polymerization increased with increasing polymerization temperature, and the apparent activation energy was calculated to be 59.9 kJ mol^?1. Reverse atom transfer radical polymerization was first used to successfully synthesize acrylonitrile polymers with a molecular weight higher than 80,000 and a narrow polydispersity as low as 1.22. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 219–225, 2006     

Synthesis of poly(methyl methacrylate)‐b‐polystyrene containing a crown ether unit at the junction point via combination of atom transfer radical polymerization and nitroxide mediated radical polymerization routes

Poly(methyl methacrylate)‐b‐polystyrene (PMMA‐b‐PS) containing a benzo‐15‐crown‐5 unit at the junction point was prepared by combining atom transfer radical polymerization and nitroxide‐mediated radical polymerization. For this purpose, 6,7,9,10,12,13,15,16‐octahydro‐5,8,11,14,17‐pentaoxa‐benzocyclopentadecene‐2‐carboxylic acid 3‐(2‐bromo‐2‐methyl‐propionyloxy)‐2‐methyl‐2‐[2‐phenyl‐2‐(2,2,6,6‐tetramethyl‐piperidin‐1‐yloxy)‐ethoxycarbonyl]‐propyl ester ( 3 ) was synthesized and used as an initiator in atom transfer radical polymerization of methyl methacrylate in the presence of CuCl and pentamethyldiethylenetriamine at 60°C. A linear behavior was observed in both plots of ln([M]₀/[M]) versus time and M_n,_GPC versus conversion indicating that the polymerization proceeded in a controlled/living manner. Thus obtained PMMA precursor was used as a macroinitiator in nitroxide‐mediated radical polymerization of styrene (St) at 125°C to give well‐defined PMMA‐b‐PS with crown ether per chain. Kinetic data were also obtained for copolymerization. Moreover, potassium picrate (K⁺ picrate) complexation of 3 and PMMA‐b‐PS copolymer was studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3242–3249, 2006     

A copper‐based reverse atom‐transfer radical polymerization process for the living radical polymerization of polyacrylonitrile

The reverse atom‐transfer radical polymerization (RATRP) technique using CuCl₂/2,2′‐bipyridine (bipy) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexasubstituted ethane thermal iniferter, diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS), was firstly used as the initiator in this copper‐based RATRP initiation system. A CuCl₂ to bipy ratio of 0.5 not only gives the best control of molecular weight and its distribution, but also provides rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 57.4 kJ mol^?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed the chain extension polymerization in the presence of CuCl/bipy catalyst system via a conventional ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 226–231, 2006     

Air‐tolerantly surface‐initiated AGET ATRP mediated by iron catalyst from silica nanoparticles

Well‐defined polymer‐nanoparticle hybrids were prepared by a newly reported method: atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) mediated by iron catalyst. The kinetics of the surface‐initiated AGET ATRP of methyl methacrylate from the silica nanoparticles, which was mediated by FeCl₃/triphenylphosphine as a catalyst complex, ascorbic acid as a reducing agent, N,N‐dimethylformamide as the solvent in the presence of a “sacrificial” (free) initiator, was studied. Both the free and grafted polymers were grown in a control manner. The chemical composition of the nanocomposites was characterized by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and ¹H nuclear magnetic resonance spectroscopy. Thermogravimetric analysis was used to estimate the content of the grafted organic compound, and transmission electron micrographs was used to observe the core‐shell structure of the hybrid nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2006–2015, 2010     

Effect of ligand on the synthesis of star polymers by resorcinarene‐based ATRP initiators

The effect of the steric hindrance on the initiating properties of two multifunctional resorcinarene‐based initiators in atom transfer radical polymerization (ATRP) was studied by using Cu(I)‐complexes of three multidentate amine ligands in the polymerization of tert‐butyl acrylate and methyl methacrylate. These ligands are less sterically hindered and have higher activities in the catalysis of ATRP of (meth)acrylates than 2,2′‐bipyridine. The polymerizations were faster and more controlled than with the 2,2′‐bipyridyl catalyst, but the tendency for bimolecular coupling increased. Even though the initiator was octafunctional, the resulting star polymers had only four arms. This indicates that the steric hindrance arising from the conformations of the initiators determines the structure of the polymer, but the ligand noticeably affects the controllability of the polymerization © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3349–3358, 2005     

ABC‐type hetero‐arm star terpolymers through “Click” chemistry

Hetero‐arm star ABC‐type terpolymers, poly(methyl methacrylate)‐polystyrene‐poly(tert‐butyl acrylate) (PMMA‐PS‐PtBA) and PMMA‐PS‐poly(ethylene glycol) (PEG), were prepared by using “Click” chemistry strategy. For this, first, PMMA‐b‐PS with alkyne functional group at the junction point was obtained from successive atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMP) routes. Furthermore, PtBA obtained from ATRP of tBA and commercially available monohydroxyl PEG were efficiently converted to the azide end‐functionalized polymers. As a second step, the alkyne and azide functional polymers were reacted to give the hetero‐arm star polymers in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine ( PMDETA) in DMF at room temperature for 24 h. The hetero‐arm star polymers were characterized by ¹H NMR, GPC, and DSC. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5699–5707, 2006     

Reverse atom transfer radical polymerization of methyl methacrylate with a new catalytic system,FeCl3/isophthalic acid

A new catalytic system, FeCl₃/isophthalic acid, was successfully used in the reverse atom transfer radical polymerization (RATRP) of methyl methacrylate (MMA) in the presence of a conventional radical initiator, 2,2′‐azo‐bis‐isobutyrontrile. Well‐defined poly(methyl methacrylate) (PMMA) was synthesized in an N,N‐dimethylformamide solvent at 90–120 °C. The polymerization was controlled up to a molecular weight of 50,000, and the polydispersity index was 1.4. Chain extension was performed to confirm the living nature of the polymer. The kinetics of the RATRP of MMA with FeCl₃/isophthalic acid as the catalyst system was investigated. The apparent activation energy was 10.47 kcal/mol. The presence of the end chloride atom on the resulting PMMA was demonstrated by ¹H NMR spectroscopy. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 765–774, 2001     

Atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system: A miniemulsion approach

Ultrasonication was applied in combination with a hydrophobe for the copper‐mediated atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system. A controlled polymerization was successfully achieved, as demonstrated by a linear correlation between the molecular weights and the monomer conversion. The polydispersities of the polymers were small (weight‐average molecular weight/number‐average molecular weight < 1.5). The influence of several factors, including ultrasonication, the amount of the surfactant, and the nature of the initiator, on the polymerization kinetics, molecular weight, and particle size was studied. The polymerization rate and molecular weights were independent of the number of particles and only depended on the atom transfer equilibrium. The final particle size, however, was a function of all the parameters. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4724–4734, 2000     

Self‐assembly of star‐shaped polystyrene‐block‐polypeptide copolymers synthesized by the combination of atom transfer radical polymerization and ring‐opening living polymerization of α‐amino acid‐N‐carboxyanhydrides

The self‐assembling nature and phase‐transition behavior of a novel class of triarm, star‐shaped polymer–peptide block copolymers synthesized by the combination of atom transfer radical polymerization and living ring‐opening polymerization of α‐amino acid‐N‐carboxyanhydride are demonstrated. The two‐step synthesis strategy adopted here allows incorporating polypeptides into the usual synthetic polymers via an amido–amidate nickelacycle intermediate, which is used as the macroinitiator for the growth of poly(γ‐benzyl‐L ‐glutamate). The characterization data are reported from analyses using gel permeation chromatography and infrared, ¹H NMR, and ¹³C NMR spectroscopy. This synthetic scheme grants a facile way to prepare a wide range of polymer–peptide architectures with perfect microstructure control, preventing the formation of homopolypeptide contaminants. Studies regarding the supramolecular organization and phase‐transition behavior of this class of polymer‐block‐polypeptide copolymers have been accomplished with X‐ray diffraction, infrared spectroscopy, and thermal analyses. The conformational change of the peptide segment in the block copolymer has been investigated with variable‐temperature infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2774–2783, 2006     

Iron‐mediated atom transfer radical polymerization of styrene with tris(3,6‐dioxaheptyl) amine as a ligand

The atom transfer radical bulk polymerization of styrene with FeX₂ (X = Br or Cl)/tris(3,6‐dioxaheptyl) amine as the catalyst system was successfully implemented at 110 °C. The number‐average molecular weight of the polymers with a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight = 1.2–1.5) increased linearly with the monomer conversion and matched the predicted molecular weight. The polymerization rate, initiation efficiency, and molecular weight distribution were influenced by the selection of the initiator and iron halide. The high functionality of the halide end group in the obtained polymers was confirmed by both ¹H NMR and a chain‐extension reaction. Because of its water solubility, the iron complexes could be removed easily from the reaction mixture through the washing of the polymerization mixture with water. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 483–489, 2006     

Atom transfer radical polymerization of functional monomers employing Cu‐based catalysts at low concentration: Polymerization of glycidyl methacrylate

Initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of an epoxide‐containing monomer, glycidyl methacrylate (GMA), was successfully carried out using low concentration of catalyst (ca. 105 ppm) at 60 °C in anisole. The copper complex of tris(2‐pyridylmethyl)amine was used as the catalyst, diethyl 2‐bromo‐2‐methylmalonate as the initiator, and 2,2′‐azobisisobutyronitrile as the reducing agent. When moderate degrees of polymerization were targeted (up to 200), special purification of the monomer, other than removal of the polymerization inhibitor, was not required to achieve good control. To synthesize well‐defined polymers with higher degrees of polymerization (600), it was essential to use very pure monomer, and polymers of molecular weights exceeding 50,000 g mol^?1 and M_w/M_n = 1.10 were prepared. The developed procedures were used to chain‐extend bromine‐terminated poly(methyl methacrylate) macroinitiator prepared by activators regenerated by electron transfer (ARGET) ATRP. The Sn^II‐mediated ARGET ATRP technique was not suitable for the polymerization of GMA and resulted in polymers with multimodal molecular weight distributions. This was due to the occurrence of epoxide ring‐opening reactions, catalyzed by Sn^II and Sn^IV. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Atom transfer radical homo‐ and block copolymerization of methyl 1‐bicyclobutanecarboxylate

A non‐olefinic monomer, methyl 1‐bicyclobutanecarboxylate (MBC), was successfully polymerized by the controlled/“living” atom transfer radical polymerization (ATRP) technique, resulting in a well‐defined homopolymer, PMBC, with only cyclobutane ring units in the polymer chain. An AB block copolymer poly(methyl 1‐bicyclobutanecarboxylate)‐b‐polystyrene (PMBC‐b‐PS), having an all‐ring unit segment, was also synthesized with narrow polydispersity and designed number‐average molecular weight in addition to precise end groups. The ¹H NMR spectra, glass‐transition temperature, and thermal stability of PMBC, PMBC‐b‐PS, and PS‐b‐PMBC were investigated. The experimental results showed that the cyclobutane rings in the two block polymers improved their thermal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1929–1936, 2002     

Heteroarm H‐shaped terpolymers through the combination of the Diels–Alder reaction and controlled/living radical polymerization techniques

Heteroarm H‐shaped terpolymers (PS)(PtBA)–PEO–(PtBA)(PS) and (PS)(PtBA)–PPO–(PtBA)(PS) [where PS is polystyrene, PtBA is poly(tert‐butyl acrylate), PEO is poly(ethylene oxide), and PPO is poly(propylene oxide)], containing PEO or PPO as a backbone and PS and PtBA as side arms, were prepared via the combination of the Diels–Alder reaction and atom transfer radical and nitroxide‐mediated radical polymerization routes. Commercially available PEO or PPO containing bismaleimide end groups was reacted with a compound having an anthracene functionality, succinic acid anthracen‐9‐yl methyl ester 3‐(2‐bromo‐2‐methylpropionyloxy)‐2‐methyl‐2‐[2‐phenyl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethoxycarbonyl]propyl ester, with a Diels–Alder reaction strategy. The obtained macroinitiator with tertiary bromide and 2,2,6,6‐tetramethylpiperidin‐1‐oxy functional end groups was used subsequently in the atom transfer radical polymerization of tert‐butyl acrylate and in the nitroxide‐mediated free‐radical polymerization of styrene to produce heteroarm H‐shaped terpolymers with moderately low molecular weight distributions (<1.31). The polymers were characterized with ¹H NMR, ultraviolet, gel permeation chromatography, and differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3947–3957, 2006     

Side‐chain terpyridine polymers through atom transfer radical polymerization and their ruthenium complexes

Polymers containing side‐chain terpyridine ligands of well‐defined architectures and controllable molecular weights and molecular weight distributions are reported. These polymers were synthesized by the atom transfer radical polymerization (ATRP) of a newly synthesized terpyridine monomer with three functional initiators. The obtained polymers were characterized with ¹H NMR and gel permeation chromatography techniques. The efficiency of the ATRP technique and the overall control of the molecular characteristics of the polymers were demonstrated by a kinetic study of the polymerization reaction. Subsequently, the ruthenium(III)/ruthenium(II) complexation chemistry was employed for the attachment of bis(dodecyloxy)‐functionalized terpyridine moieties onto each side 2,2′:6′,2″‐terpyridine unit of the main polymeric backbone. Thus, the grafting approach was successfully combined with the metal–ligand coordination chemistry for the preparation of highly soluble polymeric complexes. The resulting complexes were fully characterized by means of ¹H NMR, gel permeation chromatography, and ultraviolet–visible spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4838–4848, 2005     

Elaboration of well‐defined Rasta resins and their use as supported catalytic systems for atom transfer radical polymerization

New supported catalytic systems based on the immobilization of a ligand onto supported (co)polymers were prepared, allowing copper immobilization onto a solid support during the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). These supported catalysts were elaborated by the ATRP of 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone and/or styrene onto a Wang resin initiator. Two different approaches were used, involving well‐defined architectures synthesized by ATRP. First, a supported electrophilic homopolymer [Wang‐g‐poly(2‐vinyl‐4,4‐dimethyl‐5‐oxazolone)] was synthesized to obtain an azlactone ring at each repetitive unit, and a supported statistical copolymer [Wang‐g‐poly(2‐vinyl‐4,4‐dimethyl‐5‐oxazolone‐stat‐styrene)] was synthesized to introduce a distance between the azlactone rings. The azlactone‐based (co)polymers were then modified by a reaction with N,N,N′,N′‐tetraethyldiethylenetriamine (TEDETA) to create supported complexing sites for copper bromide. The ATRP of MMA was studied with these supported ligands, and a first‐order kinetic plot was obtained, but high polydispersity indices of the obtained poly(methyl methacrylate) were observed (polydispersity index > 2). On the other hand, the supported ATRP of styrene was performed, followed by the nucleophilic substitution of bromine by TEDETA (Wang‐g‐polystyrene–N,N,N′,N′‐tetraethyldiethylenetriamine) at the chain end of the grafted polystyrene chains. This strategy led the ligand away from the core bead, depending on the length of the polystyrene block (number‐average molecular weight determined by size exclusion chromatography = 1100–2250 g/mol). These supported complexes mediated a controlled polymerization of MMA, yielding polymers with controlled molar masses and low polydispersity indices. Moreover, after the polymerization, 96% of the initial copper was kept in the beads. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5316–5328, 2006     

Synthesis of diblock copolymers by combining stable free radical polymerization and atom transfer radical polymerization

A stable nitroxyl radical functionalized with an initiating group for atom transfer radical polymerization (ATRP), 4‐(2‐bromo‐2‐methylpropionyloxy)‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (Br‐TEMPO), was synthesized by the reaction of 4‐hydroxyl‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy with 2‐bromo‐2‐methylpropionyl bromide. Stable free radical polymerization of styrene was then carried out using a conventional thermal initiator, dibenzoyl peroxide, along with Br‐TEMPO. The obtained polystyrene had an active bromine atom for ATRP at the ω‐end of the chain and was used as the macroinitiator for ATRP of methyl acrylate and ethyl acrylate to prepare block copolymers. The molecular weights of the resulting block copolymers at different monomer conversions shifted to higher molecular weights and increased with monomer conversion. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2468–2475, 2006     

A bidirectional ATRP‐NMRP initiator: The effect of nitroxide size on the rate of nitroxide‐mediated polymerization

An N‐alkoxyamine macroinitiator bearing a polymeric nitroxide cap was synthesized and used to investigate the effect of nitroxide size on the rate of nitroxide‐mediated radical polymerization (NMRP). This macroinitiator was prepared from asymmetric double‐headed initiator 9 , which contains both an α‐bromoester and an N‐alkoxyamine functionality. Poly(methyl methacrylate) was grown by atom transfer radical polymerization from the α‐bromoester end of this initiator, resulting in a macroinitiator (M_n = 31,000; PDI = 1.34) bearing a nitroxide cap permanently attached to a polymer chain. The polymerization kinetics of this macroinitiator in NMRP were compared with known N‐alkoxyamine initiator 1 . It was found that the rate of polymerization was unaffected by the size of the macromolecular nitroxide cap. It was confirmed that NMRP using this macroinitiator is a “living” process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2015–2025, 2007     

N‐alkoxy pyridinium ion terminated polystyrenes: A facile route to photoinduced block copolymerization

Photoactive N‐alkoxy 4‐phenyl pyridinium and N‐alkoxy isoquinolinium ion terminated polystyrenes with hexafluoroantimonate counter anion were prepared and characterized. For this purpose, mono‐ and dibrominated polystyrenes were prepared by atom transfer radical polymerization (ATRP). The reaction of these polymers with silver hexafluoroantimonate in the presence of 4‐phenylpyridine N‐oxide and isoquinoline N‐oxide in dichloromethane produced desired polymeric salts with the corresponding functionalities. Irradiation of these photoactive polystyrenes produced alkoxy radicals at chain ends capable of initiating free radical polymerization of methyl methacrylate (MMA). This way, depending on the number of functionality, AB or ABA type block copolymers were formed which were characterized with the aid of gel permeation chromatography and ¹H NMR spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 423–428, 2007.     

Reverse atom transfer radical polymerization of butyl methacrylate in a miniemulsion stabilized with a cationic surfactant

The miniemulsion reverse atom transfer radical polymerization of butyl methacrylate was carried out with cetyltrimethylammonium bromide (CTAB) as the sole surfactant. The polymerizations were initiated with 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane] dihydrochloride and mediated with copper(II) bromide/tris[2‐di(2‐ethylhexyl acrylate)aminoethyl]amine. The living character was demonstrated by the linear increase in the number‐average molecular weight with conversion and the decreasing polydispersity index with conversion. The polymerizations were conducted at 90 °C with 1 wt % CTAB with respect to the monomer and produced a coagulum‐free latex with a mean particle diameter of 155 nm. The resulting latexes exhibited good shelf‐life stability. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1628–1634, 2006     

Novel miktofunctional initiator for the preparation of an ABC‐type miktoarm star polymer via a combination of controlled polymerization techniques

An ABC‐type miktoarm star polymer was prepared with a core‐out method via a combination of ring‐opening polymerization (ROP), stable free‐radical polymerization (SFRP), and atom transfer radical polymerization (ATRP). First, ROP of ϵ‐caprolactone was carried out with a miktofunctional initiator, 2‐(2‐bromo‐2‐methyl‐propionyloxymethyl)‐3‐hydroxy‐2‐methyl‐propionic acid 2‐phenyl‐2‐(2,2,6,6‐tetramethyl‐piperidin‐1‐yl oxy)‐ethyl ester, at 110 °C. Second, previously obtained poly(ϵ‐caprolactone) (PCL) was used as a macroinitiator for SFRP of styrene at 125 °C. As a third step, this PCL–polystyrene (PSt) precursor with a bromine functionality in the core was used as a macroinitiator for ATRP of tert‐butyl acrylate in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 100 °C. This produced an ABC‐type miktoarm star polymer [PCL–PSt–poly(tert‐butyl acrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.37). The obtained polymers were characterized with gel permeation chromatography and ¹H NMR. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4228–4236, 2004