The Experts below are selected from a list of 11700 Experts worldwide ranked by ideXlab platform
Bernard Boutevin - One of the best experts on this subject based on the ideXlab platform.
-
atom transfer radical coupling of polystyrene and poly Methyl Acrylate synthesized by reverse iodine transfer polymerization
Polymer, 2007Co-Authors: Benjamin Nottelet, Patrick Lacroixdesmazes, Bernard BoutevinAbstract:Iodo-terminated polystyrene and poly(Methyl Acrylate) (PMA-I) were synthesized by reverse iodine transfer polymerization. The resulting polymers were coupled by atom transfer radical coupling using Cu(I)/linear amino-ligand catalysts in the presence of reducing Cu(0). The efficiency of the coupling reaction is discussed as a function of various factors, namely, the Cu(0) particle sizes, the number of nitrogen present in the ligand structure, the type of halogen associated with Cu(I) (CuX, X = I, Br, Cl), the nature of the polymer and the nature of the chain ends. In particular, a quantitative coupling (100%) was obtained with a CuBr/HMTETA system in the presence of nanosized Cu(0) for PMA-I, thus opening for the first time a facile route to telechelic and multiblock poly(Acrylate)-based structures.
-
reverse iodine transfer polymerization of Methyl Acrylate and n butyl Acrylate
Macromolecules, 2005Co-Authors: Patrick Lacroixdesmazes, Romain Severac, Bernard BoutevinAbstract:Solution polymerization of Methyl Acrylate initiated by 2,2‘-azobis(isobutyronitrile) (AIBN) at 65 °C in the presence of molecular iodine I2 has been studied. The process, called reverse iodine transfer polymerization (RITP), efficiently controls the molecular weight (determined by size exclusion chromatography, SEC) and the structure of the polymer. For instance, poly(Methyl Acrylate) samples of Mn,SEC = 5700 g mol-1 and Mw/Mn = 1.79 (Mn,theoretical = 5500 g mol-1), Mn,SEC = 10 900 g mol-1 and Mw/Mn = 1.91 (Mn,theoretical = 10 500 g mol-1), and Mn,SEC = 21 800 g mol-1 and Mw/Mn = 1.98 (Mn,theoretical = 20 700 g mol-1) were successfully prepared. The polymerization was followed by on-line 1H NMR spectroscopy to investigate the evolution of several compounds in the reaction medium, especially the adduct between primary radicals and iodine (A−I, where A stands for the radical fragment from the initiator), the monoadduct A−M1−I (where M stands for the monomer unit), and the monomer conversion. The iodine-end...
-
reversible addition fragmentation chain transfer raft copolymerization of vinylidene chloride and Methyl Acrylate
Polymer International, 2002Co-Authors: Romain Severac, Patrick Lacroixdesmazes, Bernard BoutevinAbstract:The reversible addition-fragmentation chain-transfer (RAFT) copolymerization of vinylidene chloride and Methyl Acrylate was investigated at 70°C in benzene. Three dithioesters were synthesized in high yield by a simple and straightforward transesterification method. These dithioesters were successfully used as reversible chain-transfer agents, as demonstrated by the increase of molecular weight with conversion, a relatively low polydispersity index (I p =1.5) in comparison with a blank experiment (J p = 1.9), first-order polymerization kinetics and efficient chain extension. Nevertheless, a transfer reaction to vinylidene chloride monomer was considered to address the limitations of the RAFT process for this system. Moreover, a retardation effect was noticeable on the kinetics, depending on the structure and concentration of the transfer agent, leading to lower rate of polymerization for lower targeted molecular weights.
Thomas P. Davis - One of the best experts on this subject based on the ideXlab platform.
-
access to chain length dependent termination rate coefficients of Methyl Acrylate via reversible addition fragmentation chain transfer polymerization
Macromolecules, 2005Co-Authors: Alexander Theis, Thomas P. Davis, Achim Feldermann, Nathalie Charton, Martina H. Stenzel, Christopher BarnerkowollikAbstract:The reversible addition−fragmentation chain transferchain length dependenttermination (RAFT-CLD-T) method is employed to map out the chain length dependence of the termination rate coefficient in Methyl Acrylate (MA) bulk free radical polymerizations at 80 °C. Methoxycarbonylethyl phenyldithioacetate (MCEPDA)a novel RAFT agent carrying a Methyl acryl leaving groupis identified as suitable for the RAFT-CLD-T method applied to Methyl Acrylate, as interfering inhibition and rate retardation effects are avoided. The chain length dependency of the termination rate coefficient was constructed in a stepwise fashion since the MA/MCEPDA system displays hybrid behavior (between conventional and living free radical polymerization), resulting in initial high molecular weight polymers formed at low RAFT agent concentrations. The chain length dependency of kt in the MA system for chain lengths, i, ranging from 5 to 800 at 80 °C may be described by a value for α of 0.36 ± 0.05 (where α is the slope of the associated log...
-
origin of inhibition effects in the reversible addition fragmentation chain transfer raft polymerization of Methyl Acrylate
Institute for Future Environments; Science & Engineering Faculty, 2002Co-Authors: Sebastien Perrier, Christopher Barnerkowollik, John F Quinn, Philipp Vana, Thomas P. DavisAbstract:The reversible addition fragmentation chain transfer (RAFT) bulk polymerization of a fast propagating monomer (Methyl Acrylate, MA) has been studied using 1-phenylethyl dithiobenzoate (1-PEDB) and 2-(2-cyanopropyl) dithiobenzoate (CPDB) as RAFT agents at 60 °C. Rate retardation with increasing initial RAFT agent concentrations is common to both 1-PEDB- and CPDB-mediated MA polymerizations and occurs in comparable magnitude. A pronounced inhibition period is observed in 1-PEDB-mediated MA polymerizations, whereas the corresponding CPDB-mediated polymerizations show considerably less inhibition. The cause for this inhibition may either be associated with the leaving group of the initial RAFT agent or with the slow fragmentation of the initial intermediate macroRAFT radical. The present experimental data suggest that slow fragmentation is the probable cause for inhibition. We conclude that the radical intermediate formed by addition of radicals to the initial RAFT agent is different in stability than the macroRAFT radical formed analogously from macroRAFT agent. The inhibition period is effectively reduced by the use of CPDB as the initial RAFT agent in Methyl Acrylate polymerizations.
-
direct observation of cobalt carbon bond formation in the catalytic chain transfer polymerization of Methyl Acrylate using matrix assisted laser desorption ionization time of flight mass spectrometry
Macromolecules, 2000Co-Authors: Evan G Roberts, Johan P A Heuts, Thomas P. DavisAbstract:A preliminary study into the mechanism of catalytic chain transfer polymerization of Methyl Acrylate with BF2-bridged cobaloxime is reported. The reaction kinetics indicate two distinct phases of the reaction: an induction time followed by a steady-state polymerization. In the polymerization phase chain transfer occurs. Low molecular weight polymer chains formed during the induction period were isolated and analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI). The MALDI spectra clearly indicated poly(Methyl Acrylate) chains bound to a single cobaloxime molecule. The poly(Methyl Acrylate)−Co chains were then further reacted with α-Methylstyrene at 60 °C. MALDI analyses of the polymer from the second reaction stage indicated a displacement of cobaloxime from the chain end by an α-Methylstyrene unit.
Patrick Lacroixdesmazes - One of the best experts on this subject based on the ideXlab platform.
-
atom transfer radical coupling of polystyrene and poly Methyl Acrylate synthesized by reverse iodine transfer polymerization
Polymer, 2007Co-Authors: Benjamin Nottelet, Patrick Lacroixdesmazes, Bernard BoutevinAbstract:Iodo-terminated polystyrene and poly(Methyl Acrylate) (PMA-I) were synthesized by reverse iodine transfer polymerization. The resulting polymers were coupled by atom transfer radical coupling using Cu(I)/linear amino-ligand catalysts in the presence of reducing Cu(0). The efficiency of the coupling reaction is discussed as a function of various factors, namely, the Cu(0) particle sizes, the number of nitrogen present in the ligand structure, the type of halogen associated with Cu(I) (CuX, X = I, Br, Cl), the nature of the polymer and the nature of the chain ends. In particular, a quantitative coupling (100%) was obtained with a CuBr/HMTETA system in the presence of nanosized Cu(0) for PMA-I, thus opening for the first time a facile route to telechelic and multiblock poly(Acrylate)-based structures.
-
reverse iodine transfer polymerization of Methyl Acrylate and n butyl Acrylate
Macromolecules, 2005Co-Authors: Patrick Lacroixdesmazes, Romain Severac, Bernard BoutevinAbstract:Solution polymerization of Methyl Acrylate initiated by 2,2‘-azobis(isobutyronitrile) (AIBN) at 65 °C in the presence of molecular iodine I2 has been studied. The process, called reverse iodine transfer polymerization (RITP), efficiently controls the molecular weight (determined by size exclusion chromatography, SEC) and the structure of the polymer. For instance, poly(Methyl Acrylate) samples of Mn,SEC = 5700 g mol-1 and Mw/Mn = 1.79 (Mn,theoretical = 5500 g mol-1), Mn,SEC = 10 900 g mol-1 and Mw/Mn = 1.91 (Mn,theoretical = 10 500 g mol-1), and Mn,SEC = 21 800 g mol-1 and Mw/Mn = 1.98 (Mn,theoretical = 20 700 g mol-1) were successfully prepared. The polymerization was followed by on-line 1H NMR spectroscopy to investigate the evolution of several compounds in the reaction medium, especially the adduct between primary radicals and iodine (A−I, where A stands for the radical fragment from the initiator), the monoadduct A−M1−I (where M stands for the monomer unit), and the monomer conversion. The iodine-end...
-
reversible addition fragmentation chain transfer raft copolymerization of vinylidene chloride and Methyl Acrylate
Polymer International, 2002Co-Authors: Romain Severac, Patrick Lacroixdesmazes, Bernard BoutevinAbstract:The reversible addition-fragmentation chain-transfer (RAFT) copolymerization of vinylidene chloride and Methyl Acrylate was investigated at 70°C in benzene. Three dithioesters were synthesized in high yield by a simple and straightforward transesterification method. These dithioesters were successfully used as reversible chain-transfer agents, as demonstrated by the increase of molecular weight with conversion, a relatively low polydispersity index (I p =1.5) in comparison with a blank experiment (J p = 1.9), first-order polymerization kinetics and efficient chain extension. Nevertheless, a transfer reaction to vinylidene chloride monomer was considered to address the limitations of the RAFT process for this system. Moreover, a retardation effect was noticeable on the kinetics, depending on the structure and concentration of the transfer agent, leading to lower rate of polymerization for lower targeted molecular weights.
Romain Severac - One of the best experts on this subject based on the ideXlab platform.
-
reverse iodine transfer polymerization of Methyl Acrylate and n butyl Acrylate
Macromolecules, 2005Co-Authors: Patrick Lacroixdesmazes, Romain Severac, Bernard BoutevinAbstract:Solution polymerization of Methyl Acrylate initiated by 2,2‘-azobis(isobutyronitrile) (AIBN) at 65 °C in the presence of molecular iodine I2 has been studied. The process, called reverse iodine transfer polymerization (RITP), efficiently controls the molecular weight (determined by size exclusion chromatography, SEC) and the structure of the polymer. For instance, poly(Methyl Acrylate) samples of Mn,SEC = 5700 g mol-1 and Mw/Mn = 1.79 (Mn,theoretical = 5500 g mol-1), Mn,SEC = 10 900 g mol-1 and Mw/Mn = 1.91 (Mn,theoretical = 10 500 g mol-1), and Mn,SEC = 21 800 g mol-1 and Mw/Mn = 1.98 (Mn,theoretical = 20 700 g mol-1) were successfully prepared. The polymerization was followed by on-line 1H NMR spectroscopy to investigate the evolution of several compounds in the reaction medium, especially the adduct between primary radicals and iodine (A−I, where A stands for the radical fragment from the initiator), the monoadduct A−M1−I (where M stands for the monomer unit), and the monomer conversion. The iodine-end...
-
reversible addition fragmentation chain transfer raft copolymerization of vinylidene chloride and Methyl Acrylate
Polymer International, 2002Co-Authors: Romain Severac, Patrick Lacroixdesmazes, Bernard BoutevinAbstract:The reversible addition-fragmentation chain-transfer (RAFT) copolymerization of vinylidene chloride and Methyl Acrylate was investigated at 70°C in benzene. Three dithioesters were synthesized in high yield by a simple and straightforward transesterification method. These dithioesters were successfully used as reversible chain-transfer agents, as demonstrated by the increase of molecular weight with conversion, a relatively low polydispersity index (I p =1.5) in comparison with a blank experiment (J p = 1.9), first-order polymerization kinetics and efficient chain extension. Nevertheless, a transfer reaction to vinylidene chloride monomer was considered to address the limitations of the RAFT process for this system. Moreover, a retardation effect was noticeable on the kinetics, depending on the structure and concentration of the transfer agent, leading to lower rate of polymerization for lower targeted molecular weights.
Christopher Barnerkowollik - One of the best experts on this subject based on the ideXlab platform.
-
access to chain length dependent termination rate coefficients of Methyl Acrylate via reversible addition fragmentation chain transfer polymerization
Macromolecules, 2005Co-Authors: Alexander Theis, Thomas P. Davis, Achim Feldermann, Nathalie Charton, Martina H. Stenzel, Christopher BarnerkowollikAbstract:The reversible addition−fragmentation chain transferchain length dependenttermination (RAFT-CLD-T) method is employed to map out the chain length dependence of the termination rate coefficient in Methyl Acrylate (MA) bulk free radical polymerizations at 80 °C. Methoxycarbonylethyl phenyldithioacetate (MCEPDA)a novel RAFT agent carrying a Methyl acryl leaving groupis identified as suitable for the RAFT-CLD-T method applied to Methyl Acrylate, as interfering inhibition and rate retardation effects are avoided. The chain length dependency of the termination rate coefficient was constructed in a stepwise fashion since the MA/MCEPDA system displays hybrid behavior (between conventional and living free radical polymerization), resulting in initial high molecular weight polymers formed at low RAFT agent concentrations. The chain length dependency of kt in the MA system for chain lengths, i, ranging from 5 to 800 at 80 °C may be described by a value for α of 0.36 ± 0.05 (where α is the slope of the associated log...
-
origin of inhibition effects in the reversible addition fragmentation chain transfer raft polymerization of Methyl Acrylate
Institute for Future Environments; Science & Engineering Faculty, 2002Co-Authors: Sebastien Perrier, Christopher Barnerkowollik, John F Quinn, Philipp Vana, Thomas P. DavisAbstract:The reversible addition fragmentation chain transfer (RAFT) bulk polymerization of a fast propagating monomer (Methyl Acrylate, MA) has been studied using 1-phenylethyl dithiobenzoate (1-PEDB) and 2-(2-cyanopropyl) dithiobenzoate (CPDB) as RAFT agents at 60 °C. Rate retardation with increasing initial RAFT agent concentrations is common to both 1-PEDB- and CPDB-mediated MA polymerizations and occurs in comparable magnitude. A pronounced inhibition period is observed in 1-PEDB-mediated MA polymerizations, whereas the corresponding CPDB-mediated polymerizations show considerably less inhibition. The cause for this inhibition may either be associated with the leaving group of the initial RAFT agent or with the slow fragmentation of the initial intermediate macroRAFT radical. The present experimental data suggest that slow fragmentation is the probable cause for inhibition. We conclude that the radical intermediate formed by addition of radicals to the initial RAFT agent is different in stability than the macroRAFT radical formed analogously from macroRAFT agent. The inhibition period is effectively reduced by the use of CPDB as the initial RAFT agent in Methyl Acrylate polymerizations.
