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Controlled Radical Polymerization (controlled + radical_polymerization)
Selected AbstractsControlled Radical Polymerization of Vaporized Vinyl Monomers on Solid Surfaces under UV IrradiationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 4 2004Mikio Yasutake Abstract Summary: In order to prepare well-defined polymers on solid surfaces in the gas phase, a gas phase-assisted surface polymerization (GASP) of vinyl monomers was carried out on solid surfaces pre-coated with a photoiniferter, 2-cyanoprop-2-yl N,N,-dimethyldithiocarbamate, under UV irradiation. The GASP of methyl methacrylate (MMA) resulted in the formation of polymer on the surfaces and showed a proportional relationship between and polymer yield. Consecutive copolymerization of MMA and styrene led to the formation of a block copolymer, which was confirmed by a selective solvent fractionation method. These results demonstrate that controlled radical polymerization of vaporized monomer occurred on the solid surfaces. Expected mechanism of GASP under UV irradiation. [source] Synthesis of poly(4-vinylpyridine) by reverse atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Gregory T. Lewis Abstract Controlled radical polymerization of 4-vinylpyridine (4VP) was achieved in a 50 vol % 1-methyl-2-pyrrolidone/water solvent mixture using a 2,2,-azobis(2,4-dimethylpentanitrile) initiator and a CuCl2/2,2,-bipyridine catalyst,ligand complex, for an initial monomer concentration of [M]0 = 2.32,3.24 M and a temperature range of 70,80 °C. Radical polymerization control was achieved at catalyst to initiator molar ratios in the range of 1.3:1 to 1.6:1. First-order kinetics of the rate of polymerization (with respect to the monomer), linear increase of the number,average degree of polymerization with monomer conversion, and a polydispersity index in the range of 1.29,1.35 were indicative of controlled radical polymerization. The highest number,average degree of polymerization of 247 (number,average molecular weight = 26,000 g/mol) was achieved at a temperature of 70 °C, [M]0 = 3.24 M and a catalyst to initiator molar ratio of 1.6:1. Over the temperature range studied (70,80 °C), the initiator efficiency increased from 50 to 64% whereas the apparent polymerization rate constant increased by about 60%. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5748,5758, 2007 [source] Controlled radical polymerization of a trialkylsilyl methacrylate by reversible addition,fragmentation chain transfer polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2005M. N. Nguyen Abstract The reversible addition,fragmentation chain transfer (RAFT) polymerization of a hydrolyzable monomer (tert -butyldimethylsilyl methacrylate) with cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate as chain-transfer agents was studied in toluene solutions at 70 °C. The resulting homopolymers had low polydispersity (polydispersity index < 1.3) up to 96% monomer conversion with molecular weights at high conversions close to the theoretical prediction. The profiles of the number-average molecular weight versus the conversion revealed controlled polymerization features with chain-transfer constants expected between 1.0 and 10. A series of poly(tert -butyldimethylsilyl methacrylate)s were synthesized over the molecular weight range of 1.0 × 104 to 3.0 × 104, as determined by size exclusion chromatography. As strong differences of hydrodynamic volumes in tetrahydrofuran between poly(methyl methacrylate), polystyrene standards, and poly(tert -butyldimethylsilyl methacrylate) were observed, true molecular weights were obtained from a light scattering detector equipped in a triple-detector size exclusion chromatograph. The Mark,Houwink,Sakurada parameters for poly(tert -butyldimethylsilyl methacrylate) were assessed to obtain directly true molecular weight values from size exclusion chromatography with universal calibration. In addition, a RAFT agent efficiency above 94% was confirmed at high conversions by both light scattering detection and 1H NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5680,5689, 2005 [source] Controlled radical polymerization of 2-hydroxyethyl methacrylate with a hydrophilic ruthenium complex and the synthesis of amphiphilic random and block copolymers with methyl methacrylate,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2002Yusuke Fuji Abstract A hydrophilic ruthenium complex with ionic phosphine ligands {1: RuCl2[P(3-C6H4SO3Na)(C6H5)2]2} induced controlled radical polymerization of 2-hydroxyethyl methacrylate (HEMA) in methanol under homogeneous conditions; the initiator was a chloride (R-Cl) such as CHCl2COPh. The number-average molecular weights of poly(HEMA) increased in direct proportion to monomer conversion, and the molecular weight distributions were relatively narrow (Mw/Mn = 1.4,1.7). A similar living radical polymerization was possible with (MMA)2 -Cl [(CH3)2C(CO2CH3)CH2C(CH3)(CO2CH3)Cl] as an initiator coupled with amine additives such as n -Bu3N. In a similar homogeneous system in methanol, methyl methacrylate (MMA) could also be polymerized in living fashion with the R-Cl/1 initiating system. Especially for such hydrophobic polymers, the water-soluble ruthenium catalyst was readily removed from the polymers by simple washing with an aqueous dilute acid. This system can be applied to the direct synthesis of amphiphilic random and block copolymers of HEMA and MMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2055,2065, 2002 [source] Cyclic alkoxyamine-initiator tethered by azide/alkyne-"click"-chemistry enabling ring-expansion vinyl polymerization providing macrocyclic polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2010Atsushi Narumi Abstract A cyclic initiator for the nitroxide-mediated controlled radical polymerization (NMP) is a powerful tool for the preparation of macrocyclic polymers via a ring-expansion vinyl polymerization mechanism. For this purpose, we prepared a Hawker-type NMP-initiator that includes an azide and a terminal alkyne as an acyclic precursor, which is subsequently tethered via an intramolecular azide/alkyne-"click"-reaction, producing the final cyclic NMP-initiator. The polymerization reactions of styrene with cyclic initiator were demonstrated and the resultant polymers were characterized by the gel permeation chromatography (GPC) and the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). These results prove that the ring-expansion polymerization of styrene occurred together with the radical ring-crossover reactions originating from the exchange of the inherent nitroxides generating macrocyclic polystyrenes with higher expanded rings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3402,3416, 2010 [source] Synthesis and kinetic analysis of DPE controlled radical polymerization of MMAJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009Ying-Da Luo Abstract The 1,1-diphenylethene (DPE) controlled radical polymerization of methyl methacrylate was performed at 80 °C by using AIBN as an initiator and DPE as a control agent. It was found that the molecular weight of polymer remained constant with monomer conversion throughout the polymerization regardless of the amounts of DPE and initiator in formulation. To understand the result of constant molecular weight of living polymers in DPE controlled radical polymerization, a living kinetic model was established in this research to evaluate all the rate constants involved in the DPE mechanism. The rate constant k2, corresponding to the reactivation reaction of the DPE capped dormant chains, was found to be very small at 80 °C (1 × 10,5 s,1), that accounted for the result of constant molecular weight of polymers throughout the polymerization, analogous to a traditional free radical polymerization system that polymer chains were terminated by chain transfer. The polydispersity index (PDI) of living polymers was well controlled <1.5. The low PDI of obtained living polymers was due to the fact that the rate of growing chains capped by DPE was comparable with the rate of propagation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source] Synthesis of PMMA- b -PBA block copolymer in homogeneous and miniemulsion systems by DPE controlled radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2009Ying-Da Luo Abstract In this research, poly(methyl methacrylate)- b -poly(butyl acrylate) (PMMA- b -PBA) block copolymers were prepared by 1,1-diphenylethene (DPE) controlled radical polymerization in homogeneous and miniemulsion systems. First, monomer methyl methacrylate (MMA), initiator 2,2,-azobisisobutyronitrile (AIBN) and a control agent DPE were bulk polymerized to form the DPE-containing PMMA macroinitiator. Then the DPE-containing PMMA was heated in the presence of a second monomer BA, the block copolymer was synthesized successfully. The effects of solvent and polymerization methods (homogeneous polymerization or miniemulsion polymerization) on the reaction rate, controlled living character, molecular weight (Mn) and molecular weight distribution (PDI) of polymers throughout the polymerization were studied and discussed. The results showed that, increasing the amounts of solvent reduced the reaction rate and viscosity of the polymerization system. It allowed more activation,deactivation cycles to occur at a given conversion thus better controlled living character and narrower molecular weight distribution of polymers were demonstrated throughout the polymerization. Furthermore, the polymerization carried out in miniemulsion system exhibited higher reaction rate and better controlled living character than those in homogeneous system. It was attributed to the compartmentalization of growing radicals and the enhanced deactivation reaction of DPE controlled radical polymerization in miniemulsified droplets. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4435,4445, 2009 [source] Chain Transfer to Polymer and Branching in Controlled Radical Polymerizations of n -Butyl AcrylateMACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2009Nasir M. Ahmad Abstract Chain transfer to polymer (CTP) in conventional free-radical polymerizations (FRPs) and controlled radical polymerizations (ATRP, RAFT and NMP) of n -butyl acrylate (BA) has been investigated using 13C NMR measurements of branching in the poly(n -butyl acrylate) produced. The mol-% branches are reduced significantly in the controlled radical polymerizations as compared to conventional FRPs. Several possible explanations for this observation are discussed critically and all except one refuted. The observations are explained in terms of differences in the concentration of highly reactive short-chain radicals which can be expected to undergo both intra- and inter-molecular CTP at much higher rates than long-chain radicals. In conventional FRP, the distribution of radical concentrations is broad and there always is present a significant proportion of short-chain radicals, whereas in controlled radical polymerizations, the distribution is narrow with only a small proportion of short-chain radicals which diminishes as the living chains grow. Hence, irrespective of the type of control, controlled radical polymerizations give rise to lower levels of branching, when performed under otherwise similar conditions to conventional FRP. Similar observations are expected for other acrylates and monomers that undergo chain transfer to polymer during radical polymerization. [source] | ||||||||||