Showing papers on "Ionic polymerization published in 2003"
TL;DR: An overview on recent developments of oxidative polymerizations of phenols, particularly focusing on the coupling selectivity, can be found in this article, where three reaction mechanisms are discussed: coupling of free phenoxy radicals, coupling of the phenoxonium cation coordinated to catalyst complexes, and coupling through the phenoxide cation.
269 citations
TL;DR: DFT calculations suggest that the attractive interaction between a fluorine ortho to the imine nitrogen and a beta-hydrogen of a growing polymer chain is responsible for the achievement of room-temperature living propylene polymerization.
Abstract: The propylene polymerization behavior of a series of Ti complexes featuring fluorine-containing phenoxy−imine chelate ligands is reported. The Ti complexes combined with methylalumoxane (MAO) can be catalysts for living and, at the same time, stereospecific polymerization of propylene at room temperature or above. DFT calculations suggest that the attractive interaction between a fluorine ortho to the imine nitrogen and a β-hydrogen of a growing polymer chain is responsible for the achievement of room-temperature living propylene polymerization. Although the Ti complexes possess C2 symmetry, they are capable of producing highly syndiotactic polypropylenes. 13C NMR is used to demonstrate that the syndiotacticity is governed by a chain-end control mechanism and that the polymerization is initiated exclusively via 1,2-insertion followed by 2,1-insertion as the principal mode of polymerization. 13C NMR spectroscopy also elucidated that the polypropylenes produced with the Ti complexes possess regio-block stru...
259 citations
TL;DR: In this paper, a branched polystyrene was synthesized with controlled architecture in the light of the length and narrow distribution of primary chains as well as the degree and the distribution of branching along the polymer chain.
Abstract: Styrene radical polymerization was carried out in the presence of a polymerizable dithioester, benzyl 4-vinyldithiobenzoate, which possesses a dithioester group and a polymerizable double bond. Branched polystyrene was formed during the polymerization, as indicated by multimodal GPC curves of the products. The branched polystyrene contains a dithiobenzoate C(dS)S moiety at each branch point and thus can be analyzed by cleavage with amine. After cleavage, the GPC profiles became narrow. The molecular weight of the cleaved product increased linearly with monomer conversion, illustrating a living fashion of the polymerization. Solution property obtained by simultaneous online measurements of viscosity and light scattering indicates that the viscosity of the branched product decreased remarkably as compared to the linear polystyrene of equivalent molecular weight. The copolymerization behavior of styrene and benzyl 4-vinyldithiobenzoate was investigated by FT-IR monitoring during the polymerization. The results show that the latter was incorporated homogeneously into polystyrene chain. Therefore, branched polystyrene was synthesized with controlled architecture in the light of the length and narrow distribution of primary chains as well as the degree and the distribution of branching along the polymer chain.
183 citations
TL;DR: Kinetic analysis reveals the existence of two competing pathways in the organotellurium-mediated living radical polymerization (TERP) at elevated temperature, and these pathways are applicable to a variety of vinyl monomers.
Abstract: Kinetic analysis reveals the existence of two competing pathways in the organotellurium-mediated living radical polymerization (TERP) at elevated temperature. The rate-determining step, namely, the thermal dissociation process, could be bypassed by the addition of conventional radical initiators, and the polymerization proceeded at low temperature by the degenerative transfer-mediated polymerization. The polymerization conditions are applicable to a variety of vinyl monomers, and the desired polymers form in a highly controlled manner.
175 citations
TL;DR: In this article, 2-Mercaptothioxanthone (TX-SH), a hydrogen abstraction type photoinitiator for free radical polymerization, is synthesized and characterized, and its capability to act as an initiator for the polymerization of methyl methacrylate (MMA), styrene (St), and multifunctional monomers is examined.
Abstract: 2-Mercaptothioxanthone (TX-SH), a hydrogen abstraction type photoinitiator for free radical polymerization, is synthesized and characterized. Its capability to act as an initiator for the polymerization of methyl methacrylate (MMA), styrene (St), and multifunctional monomers is examined. The relative efficiencies of TX-SH, the parent thioxanthone (TX), and their combination with an amine synergist such as N-methyldiethanolamine (MDEA) are compared in the photopolymerization. The postulated mechanism is based on the intermolecular reaction of triplet, 3TX-SH*, with the thiol moiety of ground-state TX-SH. Thus, when TX-SH is irradiated in the presence of a monomer, it can serve as both a triplet photosensitizer and a hydrogen donor. The resulting thiyl radicals initiate the polymerization. Incorporation of TX-S groups into polymers was demonstrated by spectroscopic methods.
172 citations
TL;DR: In this paper, the 2-thioxanthone-thioacetic acid and 2-carboxymethoxythioanthone, bimolecular photoinitiators for free radical polymerization, are characterized.
Abstract: The compounds 2-thioxanthone-thioacetic acid and 2-(carboxymethoxy)thioxanthone, bimolecular photoinitiators for free radical polymerization, are synthesized and characterized. Their capability to act as initiators for the polymerization of methyl methacrylate was examined. The postulated mechanism is based on the intermolecular electron-transfer reaction of the excited photoinitiator with the sulfur or oxygen atom of the ground state of the respective photoinitiator followed by decarboxylation. The resulting alkyl radicals initiate the polymerization.
Structures of the photoinitiators.
165 citations
165 citations
TL;DR: A series of five-coordinate aluminium mono alkoxide complexes supported by R1,R2BPBA (bis-3-R1-5-R2-phenoxymethyl-bisamine) ligands were synthesized to probe the effect of electronic variation in the supporting ligand on the rate of e-caprolactone polymerization.
Abstract: A series of novel five-coordinate aluminium mono alkoxide complexes supported by R1,R2BPBA (bis-3-R1-5-R2-phenoxymethyl-bisamine) ligands were synthesized to probe the effect of electronic variation in the supporting ligand on the rate of e-caprolactone polymerization. Substitution on the aromatic position para to the phenoxide donor oxygen by tert-butyl, methoxy and bromo substituents furnished aluminium complexes that catalyzed the polymerization of e-caprolactone at different rates. We propose that a subtle interplay between complex Lewis acidity and alkoxide nucleophilicity determines the overall rate of polymerization in these systems.
160 citations
TL;DR: Ti complexes incorporating fluorine-containing phenoxy-imine chelate ligands (fluorinated Ti-FI catalysts) have been demonstrated to induce an unprecedented living polymerization effect with both ethylene and propylene through an attractive interaction between the fluorine atom in the ligand and a beta-hydrogen atom on the growing polymer chain.
Abstract: Ti complexes incorporating fluorine-containing phenoxy-imine chelate ligands (fluorinated Ti-FI catalysts) have been demonstrated to induce an unprecedented living polymerization effect with both ethylene and propylene, through an attractive interaction between the fluorine atom in the ligand and a beta-hydrogen atom on the growing polymer chain. With the aid of this attractive interaction, highly controlled living ethylene polymerization, highly-syndiospecific living propylene polymerization, the synthesis of unique block copolymers from ethylene and propylene, and the catalytic production of monodisperse polyethylene and Zn-terminated polyethylene have been realized. The attractive interaction provides a conceptually new strategy for the achievement of controlled living olefin polymerization.
159 citations
TL;DR: Radical polymerization with reversible addition-fragmentation chain transfer (RAFT) as discussed by the authors can be adapted to produce a wide variety of block copolymers and other polymers of complex architecture.
Abstract: Radical polymerization with Reversible Addition-Fragmentation chain Transfer - RAFT polymerization can be adapted to produce a wide variety of block copolymers and other polymers of complex architecture. Such polymerizations require use of a suitable compound [Z-(C=X)X-R], which is selected to have a very high transfer constants in radical polymerization of the desired monomers, and appropriate choice of reaction conditions. Block and multiblock polymers, stars and grafts are available through use of precursors containing multiple thiocarbonylthio groups. Stars and microgels are also available through self assembly and crosslinking of RAFT synthesized block copolymer micelles and by a varient of the 'arm-first' approach wherein of a diene monomer is (co)polymerized in the presence of a preformed RAFT-made polymer. This paper briefly reviews RAFT polymerization then examines the scope for utilizing the technology in the construction of novel architectures.
145 citations
TL;DR: In this paper, the authors investigated the mechanism behind the termination of polymer growth and showed that at high concentrations of radicals, termination by radical recombination limits film growth, and that the removal of radical recombinations may also limit the film thickness.
Abstract: Although atom transfer radical polymerization (ATRP) is often a controlled/living process, the growth rate of polymer films during surface-initiated ATRP frequently decreases with time. This article investigates the mechanism behind the termination of film growth. Studies of methyl methacrylate and methyl acrylate polymerization with a Cu/tris[2-(dimethylamino)ethyl]amine catalyst system show a constant but slow growth rate at low catalyst concentrations and rapid growth followed by early termination at higher catalyst concentrations. For a given polymerization time, there is, therefore, an optimum intermediate catalyst concentration for achieving maximum film thickness. Simulations of polymerization that consider activation, deactivation, and termination show trends similar to those of the experimental data, and the addition of Cu(II) to polymerization solutions results in a more constant rate of film growth by decreasing the concentration of radicals on the surface. Taken together, these studies suggest that at high concentrations of radicals, termination of polymerization by radical recombination limits film growth. Interestingly, stirring of polymerization solutions decreases film thickness in some cases, presumably because chain motion facilitates radical recombination. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 386–394, 2003
TL;DR: In this article, the reaction of the 2,5-disubstituted amino-p-benzoquinone bridging ligand with trans-bis(triphenylphosphane)phenylnickel(II) chloride results in the binuclear complexes 2a−e, which show high activities for ethylene polymerization without any cocatalysts.
TL;DR: In this paper, a strategy for polymerization catalyst design based on the steric and electronic analogy of bulky phosphinimides to cyclopentadienyl ligands was developed.
TL;DR: Several controlled/living radical polymerization (CRP) techniques (ATRP, nitroxide-mediated polymerization, NMP, IDTP, and reversible addition−fragmentation transfer polymerization) were studied for alternating copolymerization of a donor monomer and an acceptor monomer (methyl methacrylate or methyl acrylate) complexed with Lewis acid as discussed by the authors.
Abstract: Several controlled/living radical polymerization (CRP) techniques (atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), iodide degenerative transfer polymerization (IDTP), and reversible addition−fragmentation transfer polymerization (RAFT)) were studied for the alternating copolymerization of a donor monomer (styrene) and an acceptor monomer (methyl methacrylate or methyl acrylate) complexed with Lewis acid. RAFT polymerization was found to be the most versatile system. The combination of RAFT and Lewis acids complexation techniques allows synthesis of well-defined alternating copolymers poly(styrene-alt-methyl methacrylate) with controlled molecular weight (up to Mn = 70 000 g mol-1), low polydispersities (Mw/Mn < 1.3), and controlled comonomer sequences (∼90% of alternating triads). These results were obtained in the presence of diethylaluminum chloride and ethylaluminum sesquichloride. Moreover, the alternating copolymers obtained in such copolymerizations retain chain...
TL;DR: In this paper, the preparation of block copolymers with acrylonitrile (AN) and n-butyl acrylate (n-BA) was examined using two controlled radical polymerization (CRP) processes.
Abstract: The preparation of block copolymers with acrylonitrile (AN) and n-butyl acrylate (n-BA) was examined using two controlled radical polymerization (CRP) processes: atom transfer radical polymerization (ATRP) and nitroxide mediated polymerization (NMP). When crossing from poly(n-butyl acrylate) (PBA) to polymerization of AN, the use of halogen exchange in an ATRP process improved control of polymerization. However, when switching from polyacrylonitrile (PAN) to n-BA, the cross-propagation was well controlled without halogen exchange. These differences in blocking efficiency can be explained by differences in the bond dissociation energy of the terminal carbon-halogen bond. In NMP, an efficient transition from a preformed PBA block to AN polymerization required the presence of excess of nitroxide. However, chain-extension from PAN to PBA, even under homogeneous conditions and with an excess nitroxide, was less efficient, and GPC traces showed bimodality.
TL;DR: A facile synthesis of nickel salicylaldimine complexes with labile dissociating ligands is described, producing highly active ethylene polymerization catalysts and important insights into the effect of ligand size on catalyst stability and information on the mechanism of polymerization are provided.
TL;DR: In this article, the polymerization rate and morphological structure of polypyrrole films formed on the anode were affected, and the electroconductivity was significantly increased, which was applied to a matrix for hosting catalyst particles electrodeposited.
TL;DR: In this paper, the authors used dodecylbenzenesulfonic acid (DBSA) to slow down the interfacial anionic polymerization of n-BCA through reversible termination.
Abstract: The manufacture and polymerization of stable n-butyl cyanoacrylate (BCA) miniemulsions were achieved in the presence of dodecylbenzenesulfonic acid (DBSA). This surfactant, by releasing protons at the interface, slows down the interfacial anionic polymerization of n-BCA through (reversible) termination. Preliminary emulsion experiments showed that adequate DBSA/monomer ratios and stirring rates are required to avoid the generation of long polymer chains through uncontrolled polymerization. By sonicating the original mixture to produce a miniemulsion, a fair control of oligomer generation is exerted. In all experiments, however, the final oligomer distribution is mainly composed of three to five units, with the equilibrium value imposed by interfacial polymerization/depolymerization events. As a consequence, particles quickly destabilize by Ostwald ripening of the partly water-soluble hydroxylated oligomers. Decreasing the acid content after sonication by adding hydroxide sodium permits the formation of lo...
TL;DR: In this article, a ring-opening polymerization of rac-lactide was performed using a dianionic Fe(II) alkoxide/aryloxide initiator.
Abstract: Hetero-bimetallic Fe(II) alkoxide/aryloxides were evaluated as initiators for the ring-opening polymerization of rac-lactide. [(THF)NaFe(OtBu)3]2 (1) and [(THF)4Na2Fe(2,6-diisopropylphenolate)4] (2) (THF = tetrahydrofuran) both polymerized lactide efficiently at room temperature, with complex 1 affording better control over the molecular weight parameters of the resultant polymer. At conversions below 70%, a linear increase in molecular weight with conversion was observed, indicative of a well-controlled polymerization process. Complex 2 is the first example of a dianionic Fe(II) alkoxide and has been structurally characterized to reveal a distorted square planar FeO4 array in which both Na counterions bridge two aryloxide ligands and are further complexed by two THF ligands. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3798–3803, 2003
TL;DR: In this paper, the application of ionic liquids (organic salts that are liquid at ambient temperatures) as solvents for atom transfer radical polymerization (ATRP) of acrylic monomers is described.
Abstract: Application of ionic liquids (organic salts that are liquid at ambient temperatures) as solvents for atom transfer radical polymerization (ATRP) of acrylic monomers is described. Ionic liquids dissolve several inorganic and organic compounds, are highly polar and non-volatile. It has been shown that their application as solvents in ATRP of acrylates allows the reduction of side-reactions when compared against bulk polymerizations. When chiral ionic liquid was used as a solvent a small but clear effect on polymer tacticity was observed.
TL;DR: In this paper, a radical emulsion polymerization of alkylcyanoacrylates (ACA) has been investigated to produce core−shell nanoparticles coated with polysaccharides.
Abstract: A radical emulsion polymerization of alkylcyanoacrylates (ACA) has been investigated to produce core−shell nanoparticles coated with polysaccharides. It was initiated by dextran on which a radical was created by reaction with cerium(IV) ions in an aqueous acidic medium. The redox radical polymerization developed in this study occurred much faster at pH 1 than the spontaneous anionic polymerization of ACA. It was applied to several ACA and has led to the formation of very stable suspensions of nanoparticles. The mean diameter of the nanoparticles depended on the monomer. Different analysis showed that the polymer forming the nanoparticles was an amphiphilic dextran based copolymer of poly(alkylcyanoacrylate). This copolymer exhibited surfactant properties. The size, morphology, and ζ potential of the nanoparticles have been determined as well as the mobility of the polysaccharide chains at the nanoparticle surface, which was investigated by electron paramagnetic resonance.
TL;DR: In this paper, Nitroxide-mediated poly(N,N-dimethylacrylamide) copolymers were derived by sequential polymerization of the two corresponding monomers.
Abstract: Nitroxide-mediated polymerization is shown to produce well-defined poly(N,N-dimethylacrylamide) samples. In the presence of SG1, a β-phosphonylated nitroxide, the free radical polymerization of N,N-dimethylacrylamide indeed exhibits a “living”/controlled character, provided the nitroxide is used in excess and its concentration finely tuned as compared to that the free radical initiator (AIBN). Poly(N,N-dimethylacrylamide-b-butyl acrylate) diblocks copolymers were subsequently derived by sequential polymerization of the two corresponding monomers.
TL;DR: In this article, a review of aqueous ring opening metathesis polymerization, alkyne, α-olefin and diene polymerization is presented in terms of catalytic activity and polymer characteristics.
TL;DR: In this paper, a series of organic-inorganic hybrid particles were synthesized by a self-assembled layer of different initiators immobilized on silica particles and used for controlled radical polymerization.
Abstract: A series of organic-inorganic hybrid particles were synthesized by a self-assembled layer of different initiators immobilized on silica particles and used for controlled radical polymerization. We use three different initiator systems for atom-transfer radical polymerization (ATRP), unimolecular nitroxide mediated polymerization (NMP), and bimolecular NMP, for the development of the hybrid inorganic/organic particles. After preliminary qualitative characterization by X-ray spectroscopy (XPS) and Fourier-transformed infrared (FT-IR) measurements, the hybrid nanoparticles were studied by thermogravimetric analysis (TGA) to determine and discuss the initiator graft density in terms of steric hindrance.
TL;DR: A new polymer based on a functionalized benzofulvene moiety has been synthesized by spontaneous polymerization of the monomer in the solid state and shows a very high molar mass, high solubility in the most common organic solvents, and thermoreversible polymerization properties.
Abstract: A new polymer based on a functionalized benzofulvene moiety has been synthesized by spontaneous polymerization of the monomer in the solid state This polymer shows a very high molar mass, high solubility in the most common organic solvents, and thermoreversible polymerization properties An interesting application in synthesis is reported
TL;DR: In this article, the authors show that even under the best conditions (using both CuX2 and X- ion additives), the PDI is high, ca. 1.6−1.7.
Abstract: Atom transfer radical polymerization (ATRP) of acrylamide has been carried out in water or in glycerol−water (1:1 v/v) medium at 130 °C using water-soluble initiators, viz. 2-chloropropionamide (2-Cl-PA) or 2-bromopropionamide (2-Br-PA) and CuX (X = Cl, Br) bipyridine complex as catalyst. Extraneous addition of CuX2 (20 mol % of CuX) and/or excess X- ions (1 M alkali halide) in the reaction mixture helps to reduce molecular weight polydispersity (PDI). However, even under the best conditions (using both CuX2 and X- ion additives), the PDI is high, ca. 1.6−1.7. Also, the GPC traces show shoulders. The chain extension experiment, however, confirms the living nature of the polymers. Replacement of glycerol−water with water as the medium results in sluggish polymerization. The ln M0/M vs t plots are curved to start with but become linear after polymerization proceeds to variable extents depending on the additives used. The molecular weights tend to agree with the theoretical values as conversion increases. A ...
TL;DR: Dendrimers are a rich and appealing field of polymer chemistry and organic polymerization form dendritic initiators also offers a route to highly branched polymers, and indeed these have been obtained through a number of methods.
Abstract: Dendrimers are a rich and appealing field of polymer chemistry. Organic polymerization form dendritic initiators also offers a route to highly branched polymers, and indeed these have been obtained, amongest other methods, ...
TL;DR: In this article, a variety of (α-diimine)nickel(II) dibromide complexes with chlorine and methyl substituents on the ligands were studied as catalysts for the homogeneous polymerization of ethylene.
Abstract: (α-Diimine)nickel(II) dibromide complexes and their derivatives can be used for the polymerization and oligomerization of ethylene after activation with methyl-aluminoxane (MAO). The activities of these catalysts and the properties of the obtained polyethylenes depend on the structure of the used catalyst precursors. Therefore a variety of (α-diimine)nickel(II) dibromide complexes with chlorine and methyl substituents on the ligands and various substituents on the ligand backbone were studied as catalysts for the homogeneous polymerization of ethylene. The range of the polymerization products reaches from oligomers to polymers of low molecular weights.