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Masami Kamigaito - One of the best experts on this subject based on the ideXlab platform.
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stereospecific cationic raft polymerization of bulky vinyl ethers and stereoblock poly vinyl alcohol via mechanistic transformation to radical raft polymerization of vinyl acetate
Giant, 2021Co-Authors: Mineto Uchiyama, Kotaro Satoh, Masami KamigaitoAbstract:Abstract The simultaneous control of molecular weight and Tacticity in cationic polymerization remains challenging. Here, we propose a new approach for stereospecific living cationic polymerization by combining cationic reversible addition-fragmentation chain transfer (RAFT) polymerization with thiocarbonylthio compounds and stereospecific cationic polymerization of bulky vinyl ethers with Lewis acid catalysts. In this combined system, the molecular weight was controlled by the RAFT process between the growing cationic and dormant dithiocarbamate chain ends, whereas the Tacticity was controlled by stereospecific propagation based on the steric hindrance of bulky side groups and counteranions derived from the Lewis acid catalysts. Herein, we demonstrate the availability of this approach in the cationic polymerization of various bulky vinyl ethers, such as tert‑butyl, benzyl, trimethylsilyl, and tert‑butyldimethylsilyl vinyl ether, using dithiocarbamates and BF3•OEt2 or EtAlCl2 in toluene at –78 °C. Isotactic-rich poly(vinyl ether)s with controlled molecular weights and dithiocarbamate chain-end groups were obtained from a series of bulky vinyl ethers and were converted into molecular-weight-controlled isotactic poly(vinyl alcohol) (mm ≥ 70%) with a high melting temperature (Tm ~ 230 °C). Furthermore, isotactic-b-atactic stereoblock PVA (mm/mr/rr = 75/25/5 and 23/48/29, Tm ~ 210 °C) was synthesized by mechanistic transformation from the stereospecific cationic RAFT polymerization of trimethylsilyl vinyl ether into the radical RAFT polymerization of vinyl acetate using diphenyl dithiocarbamate as the common RAFT agent followed by simultaneous deprotection of the silyl and acetyl groups.
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stereospecific free radical and raft polymerization of bulky silyl methacrylates for Tacticity and molecular weight controlled poly methacrylic acid
Macromolecules, 2011Co-Authors: Kenji Ishitake, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:A series of silyl methacrylates [CH2═C(CH3)CO2SiR3] with varying silyl group bulkiness [R3Si: Me3Si, Et3Si, Me2tBuSi, iPr3Si, Ph2tBuSi, Ph3Si, and (Me3Si)3Si] were synthesized and radically polymerized to efficiently give soluble polymers with the exception of the highly bulky tris(trimethylsilyl)silyl methacrylate (TTMSSMA), which resulted in insoluble polymers. All the polymers can easily be converted into poly(methacrylic acid) (PMAA) via acid- or fluoride-induced deprotection of the silyl groups and further into poly(methyl methacrylate) (PMMA) via methylation with trimethylsilyldiazomethane for the analysis of molecular weight and Tacticity. The Tacticity was dependent on the bulkiness of the silyl substituents; the isoTacticity increased with increasing bulkiness. Thus, a series of PMAAs and PMMAs with various tacticities ranging from syndiotactic-rich (rr = 74%; Me2tBuSi) to atactic (mr = 50%; iPr3Si) and highly isotactic [mm = 93%; (Me3Si)3Si] enchainment were obtained by conventional radical poly...
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triple hydrogen bonding for stereospecific radical polymerization of a dad monomer and simultaneous control of Tacticity and molecular weight
Macromolecules, 2006Co-Authors: Decheng Wan, Kotaro Satoh, Masami KamigaitoAbstract:A triple hydrogen bonding interaction effectively controlled the stereochemistry during radical polymerization of acylamide derivatives. An acrylamide monomer, in which amide (proton donor site, D) and pyridine (proton acceptor site, A) moieties were arrayed in the DAD sequence, was polymerized in the presence of a cyclic imide as the ADA-type receptor in CHCl3 to give syndiotactic polymers (r = 72%) even at 60 °C while atactic polymers (r = 43%) were obtained without the mediator. Furthermore, the simultaneous control of the Tacticity and the molecular weights of the polymers were attained by RAFT polymerization in the presence of the mediator.
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iodine transfer radical polymerization of vinyl acetate in fluoroalcohols for simultaneous control of molecular weight stereospecificity and regiospecificity
Macromolecules, 2006Co-Authors: Kazuhiko Koumura, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:The simultaneous control of the Tacticity and molecular weight of poly(vinyl acetate) during the radical polymerization of vinyl acetate (VAc) is reported for the first time. A series of fluoroalcohols [(CF3)3COH, (CF3)2CHOH, PhC(CF3)2OH, m-C6H4{C(CF3)2OH}2] were employed as solvents for the iodine transfer radical polymerization of VAc, in which the molecular weight of the resultant polymer was determined by the monomer-to-transfer agent ratio and its Tacticity was controlled by the solvent. Among the fluoroalcohols, the use of fluorodiol, m-C6H4{C(CF3)2OH}2, not only led to a higher syndioTacticity (r ∼ 60%) but also improved the molecular weight control, resulting in narrow molecular weight distributions (MWD) (Mw/Mn ∼ 1.20) in the presence of CH2I(CO2Et) and an azo-initiator [2,2‘-azobis(4-methoxy-2,4-dimethylvaleronitrile)] at 20 °C. High molecular weight polymers (Mn > 7 × 104) with a relatively narrow MWD (Mw/Mn < 1.6) were obtained with the same system. The content of the head-to-head linkages was...
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xanthate mediated radical polymerization of n vinylpyrrolidone in fluoroalcohols for simultaneous control of molecular weight and Tacticity
Macromolecules, 2005Co-Authors: Decheng Wan, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:The simultaneous control of the Tacticity and molecular weight of poly(N-vinylpyrrolidone) during radical polymerization is reported for the first time. For molecular weight control, xanthates of (O-ethylxanthylmethyl)benzene and [1-(O-ethylxanthyl)ethyl]benzene were used as RAFT/MADIX chain transfer agents (CTAs) for the radical polymerization of N-vinylpyrrolidone (NVP). Both led to a controlled/living radical polymerization, and the latter showed higher chain transfer ability under the optimal conditions; the molecular weight distribution was 1.36 when the molecular weight was up to 26 700. The polymerization was studied between 20 and 120 °C and at various concentrations of CTA. All the polymerizations showed an induction period and rate retardation dependent on both the concentration of CTA and temperature. For Tacticity control, the polymerization was carried out in fluoroalcohols via a conventional radical process without CTAs to give syndiotactic polymers. The polymer Tacticity was dependent on th...
Yoshio Okamoto - One of the best experts on this subject based on the ideXlab platform.
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stereospecific free radical and raft polymerization of bulky silyl methacrylates for Tacticity and molecular weight controlled poly methacrylic acid
Macromolecules, 2011Co-Authors: Kenji Ishitake, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:A series of silyl methacrylates [CH2═C(CH3)CO2SiR3] with varying silyl group bulkiness [R3Si: Me3Si, Et3Si, Me2tBuSi, iPr3Si, Ph2tBuSi, Ph3Si, and (Me3Si)3Si] were synthesized and radically polymerized to efficiently give soluble polymers with the exception of the highly bulky tris(trimethylsilyl)silyl methacrylate (TTMSSMA), which resulted in insoluble polymers. All the polymers can easily be converted into poly(methacrylic acid) (PMAA) via acid- or fluoride-induced deprotection of the silyl groups and further into poly(methyl methacrylate) (PMMA) via methylation with trimethylsilyldiazomethane for the analysis of molecular weight and Tacticity. The Tacticity was dependent on the bulkiness of the silyl substituents; the isoTacticity increased with increasing bulkiness. Thus, a series of PMAAs and PMMAs with various tacticities ranging from syndiotactic-rich (rr = 74%; Me2tBuSi) to atactic (mr = 50%; iPr3Si) and highly isotactic [mm = 93%; (Me3Si)3Si] enchainment were obtained by conventional radical poly...
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iodine transfer radical polymerization of vinyl acetate in fluoroalcohols for simultaneous control of molecular weight stereospecificity and regiospecificity
Macromolecules, 2006Co-Authors: Kazuhiko Koumura, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:The simultaneous control of the Tacticity and molecular weight of poly(vinyl acetate) during the radical polymerization of vinyl acetate (VAc) is reported for the first time. A series of fluoroalcohols [(CF3)3COH, (CF3)2CHOH, PhC(CF3)2OH, m-C6H4{C(CF3)2OH}2] were employed as solvents for the iodine transfer radical polymerization of VAc, in which the molecular weight of the resultant polymer was determined by the monomer-to-transfer agent ratio and its Tacticity was controlled by the solvent. Among the fluoroalcohols, the use of fluorodiol, m-C6H4{C(CF3)2OH}2, not only led to a higher syndioTacticity (r ∼ 60%) but also improved the molecular weight control, resulting in narrow molecular weight distributions (MWD) (Mw/Mn ∼ 1.20) in the presence of CH2I(CO2Et) and an azo-initiator [2,2‘-azobis(4-methoxy-2,4-dimethylvaleronitrile)] at 20 °C. High molecular weight polymers (Mn > 7 × 104) with a relatively narrow MWD (Mw/Mn < 1.6) were obtained with the same system. The content of the head-to-head linkages was...
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xanthate mediated radical polymerization of n vinylpyrrolidone in fluoroalcohols for simultaneous control of molecular weight and Tacticity
Macromolecules, 2005Co-Authors: Decheng Wan, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:The simultaneous control of the Tacticity and molecular weight of poly(N-vinylpyrrolidone) during radical polymerization is reported for the first time. For molecular weight control, xanthates of (O-ethylxanthylmethyl)benzene and [1-(O-ethylxanthyl)ethyl]benzene were used as RAFT/MADIX chain transfer agents (CTAs) for the radical polymerization of N-vinylpyrrolidone (NVP). Both led to a controlled/living radical polymerization, and the latter showed higher chain transfer ability under the optimal conditions; the molecular weight distribution was 1.36 when the molecular weight was up to 26 700. The polymerization was studied between 20 and 120 °C and at various concentrations of CTA. All the polymerizations showed an induction period and rate retardation dependent on both the concentration of CTA and temperature. For Tacticity control, the polymerization was carried out in fluoroalcohols via a conventional radical process without CTAs to give syndiotactic polymers. The polymer Tacticity was dependent on th...
Kotaro Satoh - One of the best experts on this subject based on the ideXlab platform.
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stereospecific cationic raft polymerization of bulky vinyl ethers and stereoblock poly vinyl alcohol via mechanistic transformation to radical raft polymerization of vinyl acetate
Giant, 2021Co-Authors: Mineto Uchiyama, Kotaro Satoh, Masami KamigaitoAbstract:Abstract The simultaneous control of molecular weight and Tacticity in cationic polymerization remains challenging. Here, we propose a new approach for stereospecific living cationic polymerization by combining cationic reversible addition-fragmentation chain transfer (RAFT) polymerization with thiocarbonylthio compounds and stereospecific cationic polymerization of bulky vinyl ethers with Lewis acid catalysts. In this combined system, the molecular weight was controlled by the RAFT process between the growing cationic and dormant dithiocarbamate chain ends, whereas the Tacticity was controlled by stereospecific propagation based on the steric hindrance of bulky side groups and counteranions derived from the Lewis acid catalysts. Herein, we demonstrate the availability of this approach in the cationic polymerization of various bulky vinyl ethers, such as tert‑butyl, benzyl, trimethylsilyl, and tert‑butyldimethylsilyl vinyl ether, using dithiocarbamates and BF3•OEt2 or EtAlCl2 in toluene at –78 °C. Isotactic-rich poly(vinyl ether)s with controlled molecular weights and dithiocarbamate chain-end groups were obtained from a series of bulky vinyl ethers and were converted into molecular-weight-controlled isotactic poly(vinyl alcohol) (mm ≥ 70%) with a high melting temperature (Tm ~ 230 °C). Furthermore, isotactic-b-atactic stereoblock PVA (mm/mr/rr = 75/25/5 and 23/48/29, Tm ~ 210 °C) was synthesized by mechanistic transformation from the stereospecific cationic RAFT polymerization of trimethylsilyl vinyl ether into the radical RAFT polymerization of vinyl acetate using diphenyl dithiocarbamate as the common RAFT agent followed by simultaneous deprotection of the silyl and acetyl groups.
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stereospecific free radical and raft polymerization of bulky silyl methacrylates for Tacticity and molecular weight controlled poly methacrylic acid
Macromolecules, 2011Co-Authors: Kenji Ishitake, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:A series of silyl methacrylates [CH2═C(CH3)CO2SiR3] with varying silyl group bulkiness [R3Si: Me3Si, Et3Si, Me2tBuSi, iPr3Si, Ph2tBuSi, Ph3Si, and (Me3Si)3Si] were synthesized and radically polymerized to efficiently give soluble polymers with the exception of the highly bulky tris(trimethylsilyl)silyl methacrylate (TTMSSMA), which resulted in insoluble polymers. All the polymers can easily be converted into poly(methacrylic acid) (PMAA) via acid- or fluoride-induced deprotection of the silyl groups and further into poly(methyl methacrylate) (PMMA) via methylation with trimethylsilyldiazomethane for the analysis of molecular weight and Tacticity. The Tacticity was dependent on the bulkiness of the silyl substituents; the isoTacticity increased with increasing bulkiness. Thus, a series of PMAAs and PMMAs with various tacticities ranging from syndiotactic-rich (rr = 74%; Me2tBuSi) to atactic (mr = 50%; iPr3Si) and highly isotactic [mm = 93%; (Me3Si)3Si] enchainment were obtained by conventional radical poly...
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triple hydrogen bonding for stereospecific radical polymerization of a dad monomer and simultaneous control of Tacticity and molecular weight
Macromolecules, 2006Co-Authors: Decheng Wan, Kotaro Satoh, Masami KamigaitoAbstract:A triple hydrogen bonding interaction effectively controlled the stereochemistry during radical polymerization of acylamide derivatives. An acrylamide monomer, in which amide (proton donor site, D) and pyridine (proton acceptor site, A) moieties were arrayed in the DAD sequence, was polymerized in the presence of a cyclic imide as the ADA-type receptor in CHCl3 to give syndiotactic polymers (r = 72%) even at 60 °C while atactic polymers (r = 43%) were obtained without the mediator. Furthermore, the simultaneous control of the Tacticity and the molecular weights of the polymers were attained by RAFT polymerization in the presence of the mediator.
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iodine transfer radical polymerization of vinyl acetate in fluoroalcohols for simultaneous control of molecular weight stereospecificity and regiospecificity
Macromolecules, 2006Co-Authors: Kazuhiko Koumura, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:The simultaneous control of the Tacticity and molecular weight of poly(vinyl acetate) during the radical polymerization of vinyl acetate (VAc) is reported for the first time. A series of fluoroalcohols [(CF3)3COH, (CF3)2CHOH, PhC(CF3)2OH, m-C6H4{C(CF3)2OH}2] were employed as solvents for the iodine transfer radical polymerization of VAc, in which the molecular weight of the resultant polymer was determined by the monomer-to-transfer agent ratio and its Tacticity was controlled by the solvent. Among the fluoroalcohols, the use of fluorodiol, m-C6H4{C(CF3)2OH}2, not only led to a higher syndioTacticity (r ∼ 60%) but also improved the molecular weight control, resulting in narrow molecular weight distributions (MWD) (Mw/Mn ∼ 1.20) in the presence of CH2I(CO2Et) and an azo-initiator [2,2‘-azobis(4-methoxy-2,4-dimethylvaleronitrile)] at 20 °C. High molecular weight polymers (Mn > 7 × 104) with a relatively narrow MWD (Mw/Mn < 1.6) were obtained with the same system. The content of the head-to-head linkages was...
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xanthate mediated radical polymerization of n vinylpyrrolidone in fluoroalcohols for simultaneous control of molecular weight and Tacticity
Macromolecules, 2005Co-Authors: Decheng Wan, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:The simultaneous control of the Tacticity and molecular weight of poly(N-vinylpyrrolidone) during radical polymerization is reported for the first time. For molecular weight control, xanthates of (O-ethylxanthylmethyl)benzene and [1-(O-ethylxanthyl)ethyl]benzene were used as RAFT/MADIX chain transfer agents (CTAs) for the radical polymerization of N-vinylpyrrolidone (NVP). Both led to a controlled/living radical polymerization, and the latter showed higher chain transfer ability under the optimal conditions; the molecular weight distribution was 1.36 when the molecular weight was up to 26 700. The polymerization was studied between 20 and 120 °C and at various concentrations of CTA. All the polymerizations showed an induction period and rate retardation dependent on both the concentration of CTA and temperature. For Tacticity control, the polymerization was carried out in fluoroalcohols via a conventional radical process without CTAs to give syndiotactic polymers. The polymer Tacticity was dependent on th...
Takashi Uemura - One of the best experts on this subject based on the ideXlab platform.
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thermal ring opening polymerization of an unsymmetrical silicon bridged 1 ferrocenophane in coordination nanochannels
Chemical Communications, 2017Co-Authors: Yuichiro Kobayashi, Susumu Kitagawa, Kayako Honjo, Jessica Gwyther, Ian Manners, Takashi UemuraAbstract:Thermal ring-opening polymerization of the unsymmetrically substituted [1]ferrocenophane was performed in one-dimensional nanochannels of porous coordination polymers (PCPs). In contrast to conventional thermal polymerization in bulk, formation of cyclic polymer was inhibited in the channels. In addition, the Tacticity of the resulting polymer was dependent on the pore size of PCPs.
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functionalization of coordination nanochannels for controlling Tacticity in radical vinyl polymerization
Journal of the American Chemical Society, 2010Co-Authors: Takashi Uemura, Yukari Ono, Yuh Hijikata, Susumu KitagawaAbstract:Systematic functionalization of porous coordination polymers (PCPs), [Cu2(L)2(ted)]n (where L = dicarboxylates and ted = triethylenediamine), by introducing various substituents onto the component organic ligand, L, was performed to regulate the radical polymerization of methyl methacrylate (MMA) in the nanochannels. The effect of the substituent groups on stereoregularity of the resulting poly(methyl methacrylate) (PMMA) was observed, where the Tacticity of the PMMA strongly depended on the number and position of the substituent. In particular, polymerization of MMA in [Cu2(2,5-dimethoxyterephthalate)2(ted)]n gave PMMA with high isotactic and heterotactic triad fractions, which is one of the most effective systems for changing the Tacticity of PMMA in radical polymerization. To understand the mechanism of this drastic stereoregularity change, a variety of experimental and theoretical analyses, such as IR, N2 adsorption, a statics study, and molecular dynamics (MD) calculations, were performed. Accurate M...
Decheng Wan - One of the best experts on this subject based on the ideXlab platform.
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triple hydrogen bonding for stereospecific radical polymerization of a dad monomer and simultaneous control of Tacticity and molecular weight
Macromolecules, 2006Co-Authors: Decheng Wan, Kotaro Satoh, Masami KamigaitoAbstract:A triple hydrogen bonding interaction effectively controlled the stereochemistry during radical polymerization of acylamide derivatives. An acrylamide monomer, in which amide (proton donor site, D) and pyridine (proton acceptor site, A) moieties were arrayed in the DAD sequence, was polymerized in the presence of a cyclic imide as the ADA-type receptor in CHCl3 to give syndiotactic polymers (r = 72%) even at 60 °C while atactic polymers (r = 43%) were obtained without the mediator. Furthermore, the simultaneous control of the Tacticity and the molecular weights of the polymers were attained by RAFT polymerization in the presence of the mediator.
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xanthate mediated radical polymerization of n vinylpyrrolidone in fluoroalcohols for simultaneous control of molecular weight and Tacticity
Macromolecules, 2005Co-Authors: Decheng Wan, Masami Kamigaito, Kotaro Satoh, Yoshio OkamotoAbstract:The simultaneous control of the Tacticity and molecular weight of poly(N-vinylpyrrolidone) during radical polymerization is reported for the first time. For molecular weight control, xanthates of (O-ethylxanthylmethyl)benzene and [1-(O-ethylxanthyl)ethyl]benzene were used as RAFT/MADIX chain transfer agents (CTAs) for the radical polymerization of N-vinylpyrrolidone (NVP). Both led to a controlled/living radical polymerization, and the latter showed higher chain transfer ability under the optimal conditions; the molecular weight distribution was 1.36 when the molecular weight was up to 26 700. The polymerization was studied between 20 and 120 °C and at various concentrations of CTA. All the polymerizations showed an induction period and rate retardation dependent on both the concentration of CTA and temperature. For Tacticity control, the polymerization was carried out in fluoroalcohols via a conventional radical process without CTAs to give syndiotactic polymers. The polymer Tacticity was dependent on th...