The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Yasuyuki Kita - One of the best experts on this subject based on the ideXlab platform.
-
bronsted acid controlled 3 2 coupling reaction of quinone monoacetals with alkene nucleophiles a catalytic system of perfluorinated acids and hydrogen bond donor for the construction of benzofurans
Journal of Organic Chemistry, 2013Co-Authors: Tohru Kamitanaka, Toshifumi Dohi, Yusuke Mishima, Yasuyuki KitaAbstract:We have developed an efficient Bronsted acid-controlled strategy for the [3 + 2] coupling reaction of quinone monoacetals (QMAs) with nucleophilic alkenes, which is triggered by the particular use of a specific acid promoter, perfluorinated acid, and a solvent, Fluoroalcohol. This new coupling reaction smoothly proceeded with high regiospecificity in regard with QMAs for introducing π-nucleophiles to only the carbon α to the carbonyl group, thereby providing diverse dihydrobenzofurans and derivatives with high yields, up to quantitative, under mild conditions in short reaction times. The choice of Bronsted acid enabled us to avoid hydrolysis of the QMAs, which gives quinones, and the formation of discrete cationic species from the QMAs. Notably, further investigations in this study with regard to the acid have led to the findings that the originally stoichiometrically used acid could be reduced to a catalytic amount of 5 mol % loading or less and that the stoichiometry of the alkenes could be significantl...
-
one pot syntheses of diaryliodonium salts from aryl iodides using peracetic acid as green oxidant
Australian Journal of Chemistry, 2011Co-Authors: Toshifumi Dohi, Nobutaka Yamaoka, Itsuki Itani, Yasuyuki KitaAbstract:The rate-accelerating effects of Fluoroalcohol solvents for generating trivalent hypervalent iodine species and the conversion into diaryliodonium(iii) salts have been used for the first time to realize a facile and clean one-pot synthesis of diaryliodonium(iii) salts 3 from aryl iodides 1 and suitable arene partners 2 with peracetic acid (PAA). The use of PAA as a green and practical oxidant is significantly effective in Fluoroalcohol solvents. The scope and limitations of the methodology are elucidated by investigation of a wide variety of representative substrates.
-
Fluoroalcohols versatile solvents in hypervalent iodine chemistry and syntheses of diaryliodonium iii salts
ChemInform, 2010Co-Authors: Toshifumi Dohi, Nobutaka Yamaoka, Yasuyuki KitaAbstract:The present work reveals that Fluoroalcohols can positively affect the dehydrative condensation of hypervalent iodine reagents toward aromatic and heteroaromatic compounds.
-
Fluoroalcohols versatile solvents in hypervalent iodine chemistry and syntheses of diaryliodonium iii salts
Tetrahedron, 2010Co-Authors: Toshifumi Dohi, Nobutaka Yamaoka, Yasuyuki KitaAbstract:Abstract We first introduced 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE) as unique solvents for reactions involving hypervalent iodine-mediated phenolic oxidations in the 1980s, in which the Fluoroalcohols have been successfully utilized as stabilizing solvents of the reactive cationic intermediates, generated in situ by the action of phenyliodine(III) diacetate (PIDA) and phenyliodine bis(trifluoroacetate) (PIFA). This pioneering study produced a breakthrough in hypervalent iodine chemistry, and many synthetic applications that enable a variety of transformations have appeared utilizing this unique medium. For example, the single-electron-transfer (SET) oxidation ability of PIFA toward phenyl ethers has been discovered for the first time in HFIP and TFE, taking advantage of the unique acid-like behaviors to stabilize the aromatic cation radicals. More recently, the catalytic strategy of hypervalent iodine reagents has found extensive applications with the aid of the Fluoroalcohols to produce highly reactive catalytic species under mild conditions. The Fluoroalcohols are now widely used as versatile solvents not only in hypervalent iodine chemistry, but also in other organic syntheses. This manuscript for the Special Issue deals with the background of the hypervalent iodine chemistry and a new topic concerning the utility of Fluoroalcohols for the synthesis of diaryliodonium(III) salts.
-
enhanced reactivity of hydroxy tosyloxy iodo benzene in Fluoroalcohol media efficient direct synthesis of thienyl aryl iodonium salts
Molecules, 2010Co-Authors: Motoki Ito, Toshifumi Dohi, Hiromichi Fujioka, Nobutaka Yamaoka, Chieko Ogawa, Yasuyuki KitaAbstract:In this manuscript, we report clear evidence for the generation of aromatic cation radicals produced by using [hydroxy(tosyloxy)iodo]benzene (HTIB) in Fluoroalcohol solvents such as 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). The single-electron-transfer (SET) oxidation ability of HTIB to give cation radicals was first established by ESR and UV measurements. The reaction was broadly applied to various thiophenes, and unique thienyliodonium salts were directly synthesized by this method in excellent yields without the production of any harmful byproducts.
Yoshio Okamoto - One of the best experts on this subject based on the ideXlab platform.
-
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...
-
synthesis of well defined syndiotactic poly methyl methacrylate with low temperature atom transfer radical polymerization in Fluoroalcohol
Journal of Polymer Science Part A, 2006Co-Authors: Yutaka Miura, Yoshio Okamoto, Toshifumi Satoh, Atsushi Narumi, Osamu Nishizawa, Toyoji KakuchiAbstract:The copper-mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2-(dimethylamino)ethyl]amine (Me6TREN) as a ligand was performed even at −78°C with a number-average molecular weight (Mn) of 13,400 and a polydispersity (weight-average molecular weight/number-average molecular weight) of 1.31, although the measured Mn's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr2) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]0/[methyl α-bromoisobutyrate]0/[CuBr]0/[CuBr2]0/[Me6TREN]0 = 200/1/1/0.2/1.2 at −20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of CuIBr/Me6TREN in HFIP, there were [Cu(Me6TREN)Br]+ and [Cu(Me6TREN)OCH(CF3)2]+, indicating that HFIP should coordinate to the CuI/Me6TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for −78°C, 77% for −30°C, 75% for −20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006
-
free radical copolymerization of vinyl esters using Fluoroalcohols as solvents the solvent effect on the monomer reactivity ratio
Journal of Polymer Science Part A, 2000Co-Authors: Kazunobu Yamada, Tamaki Nakano, Yoshio OkamotoAbstract:Free-radical copolymerizations of vinyl acetate (VAc = M1) and other vinyl esters (= M2) including vinyl pivalate (VPi), vinyl 2,2-bis(trifluoromethyl)propionate (VF6Pi), and vinyl benzoate (VBz) with Fluoroalcohols and tetrahydrofuran (THF) as the solvents were investigated. The Fluoroalcohols affected not only the stereochemistry but also the polymerization rate. The polymerization rate was higher in the Fluoroalcohols than in THF. The accelerating effect of the Fluoroalcohols on the polymerization was probably due to the interaction of the solvents with the ester side groups of the monomers and growing radical species. The difference in the monomer reactivity ratios (r1, r2) in THF and 2,2,2-trifluoroethanol was relatively small for all reaction conditions and for the monomers tested in this work, whereas r1 increased in the VAc-VF6Pi copolymerization and r2 decreased in the VAc-VPi copolymerization when perfluoro-tert-butyl alcohol was used as the solvent. These results were ascribed to steric and monomer-activating effects due to the hydrogen bonding between the monomers and solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 220–228, 2000
-
stereospecific free radical polymerization of vinyl esters using Fluoroalcohols as solvents
Macromolecules, 1998Co-Authors: Kazunobu Yamada, Tamaki Nakano, Yoshio OkamotoAbstract:Solvent effects on the stereochemistry of free radical polymerization of vinyl acetate (VAc) and vinyl pivalate (VPi) were investigated. In the polymerization of VAc, an alcoholic solvent with a smaller pKa and higher bulkiness afforded a polymer having a higher syndiotacticity. The polymerization of VAc in perfluoro-tert-butyl alcohol ((CF3)3COH) at −78 °C led to a diad syndiotacticity r of 72%, which is the highest for the radical polymerization of vinyl esters. On the other hand, the polymerization of VPi in Fluoroalcohol at a low temperature afforded a polymer rich in heterotacticity (up to mr = 61%). Synthesis of a heterotactic homopolymer by the free radical polymerization of monosubstituted vinyl monomers is unprecedented. The stereochemical effects observed in this study may be due to hydrogen-bond interaction between the Fluoroalcohol molecules and the ester groups of the vinyl ester monomer and the side chain of the growing polymer. Mechanisms of stereoregulation were proposed.
-
stereospecific polymerization of vinyl acetate in Fluoroalcohols synthesis of syndiotactic poly vinyl alcohol
Proceedings of the Japan Academy. Series B Physical and biological sciences, 1998Co-Authors: Kazunobu Yamada, Tamaki Nakano, Yoshio OkamotoAbstract:The free-radical polymerization of vinyl acetate (VAc) was carried out in various alcoholic solvents. Fluoroalcohols with a lower pKa and higher bulkiness were effective in enhancing the syndiotactic specificity of the polymerization. The polymerization of VAc in perfluoro-tert-butyl alcohol ((CF3)3COH) at -78°C led to a dyad syndiotacticity of 72%, which is the highest value reported for the radical polymerization of vinyl esters. Hydrogen-bonding between the acetyl groups of VAc and polymer and the Fluoroalcohol molecule may be responsible for the enhancement of the syndiotactic specific propagation.
Toshifumi Dohi - One of the best experts on this subject based on the ideXlab platform.
-
nucleophilic arylation of halopurines facilitated by bronsted acid in Fluoroalcohol
Molecules, 2019Co-Authors: Naoko Takenaga, Toshitaka Shoji, Takayuki Menjo, Akiko Hirai, Shohei Ueda, Kotaro Kikushima, Tomonori Hanasaki, Toshifumi DohiAbstract:Various aryl-substituted purine derivatives were synthesized through the direct arylation of halopurines with aromatic compounds, facilitated by the combination of triflic acid and Fluoroalcohol. This metal-free method is complementary to conventional coupling reactions using metal catalysts and reagents for the syntheses of aryl-substituted purine analogues.
-
bronsted acid controlled 3 2 coupling reaction of quinone monoacetals with alkene nucleophiles a catalytic system of perfluorinated acids and hydrogen bond donor for the construction of benzofurans
Journal of Organic Chemistry, 2013Co-Authors: Tohru Kamitanaka, Toshifumi Dohi, Yusuke Mishima, Yasuyuki KitaAbstract:We have developed an efficient Bronsted acid-controlled strategy for the [3 + 2] coupling reaction of quinone monoacetals (QMAs) with nucleophilic alkenes, which is triggered by the particular use of a specific acid promoter, perfluorinated acid, and a solvent, Fluoroalcohol. This new coupling reaction smoothly proceeded with high regiospecificity in regard with QMAs for introducing π-nucleophiles to only the carbon α to the carbonyl group, thereby providing diverse dihydrobenzofurans and derivatives with high yields, up to quantitative, under mild conditions in short reaction times. The choice of Bronsted acid enabled us to avoid hydrolysis of the QMAs, which gives quinones, and the formation of discrete cationic species from the QMAs. Notably, further investigations in this study with regard to the acid have led to the findings that the originally stoichiometrically used acid could be reduced to a catalytic amount of 5 mol % loading or less and that the stoichiometry of the alkenes could be significantl...
-
one pot syntheses of diaryliodonium salts from aryl iodides using peracetic acid as green oxidant
Australian Journal of Chemistry, 2011Co-Authors: Toshifumi Dohi, Nobutaka Yamaoka, Itsuki Itani, Yasuyuki KitaAbstract:The rate-accelerating effects of Fluoroalcohol solvents for generating trivalent hypervalent iodine species and the conversion into diaryliodonium(iii) salts have been used for the first time to realize a facile and clean one-pot synthesis of diaryliodonium(iii) salts 3 from aryl iodides 1 and suitable arene partners 2 with peracetic acid (PAA). The use of PAA as a green and practical oxidant is significantly effective in Fluoroalcohol solvents. The scope and limitations of the methodology are elucidated by investigation of a wide variety of representative substrates.
-
Fluoroalcohols versatile solvents in hypervalent iodine chemistry and syntheses of diaryliodonium iii salts
ChemInform, 2010Co-Authors: Toshifumi Dohi, Nobutaka Yamaoka, Yasuyuki KitaAbstract:The present work reveals that Fluoroalcohols can positively affect the dehydrative condensation of hypervalent iodine reagents toward aromatic and heteroaromatic compounds.
-
Fluoroalcohols versatile solvents in hypervalent iodine chemistry and syntheses of diaryliodonium iii salts
Tetrahedron, 2010Co-Authors: Toshifumi Dohi, Nobutaka Yamaoka, Yasuyuki KitaAbstract:Abstract We first introduced 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE) as unique solvents for reactions involving hypervalent iodine-mediated phenolic oxidations in the 1980s, in which the Fluoroalcohols have been successfully utilized as stabilizing solvents of the reactive cationic intermediates, generated in situ by the action of phenyliodine(III) diacetate (PIDA) and phenyliodine bis(trifluoroacetate) (PIFA). This pioneering study produced a breakthrough in hypervalent iodine chemistry, and many synthetic applications that enable a variety of transformations have appeared utilizing this unique medium. For example, the single-electron-transfer (SET) oxidation ability of PIFA toward phenyl ethers has been discovered for the first time in HFIP and TFE, taking advantage of the unique acid-like behaviors to stabilize the aromatic cation radicals. More recently, the catalytic strategy of hypervalent iodine reagents has found extensive applications with the aid of the Fluoroalcohols to produce highly reactive catalytic species under mild conditions. The Fluoroalcohols are now widely used as versatile solvents not only in hypervalent iodine chemistry, but also in other organic syntheses. This manuscript for the Special Issue deals with the background of the hypervalent iodine chemistry and a new topic concerning the utility of Fluoroalcohols for the synthesis of diaryliodonium(III) salts.
Masami Kamigaito - One of the best experts on this subject based on the ideXlab platform.
-
bab random c monomer sequence via radical terpolymerization of limonene a maleimide b and methacrylate c terpene polymers with randomly distributed periodic sequences
Angewandte Chemie, 2017Co-Authors: Masataka Ojika, Kotaro Satoh, Masami KamigaitoAbstract:A naturally abundant terpene, limonene (A), was radically polymerized with a maleimide derivative (B) and methacrylate (C) in a fluorinated alcohol to give terpolymers with unprecedented BAB-random-C sequences in which the BAB monomer sequence was randomly copolymerized with a C unit. In each binary system, limonene was hardly copolymerized with methacrylate while it was efficiently copolymerized with maleimide to result in a 1:2-alternating BAB periodic sequence, in part due to the penultimate effects and hydrogen-bonding interactions with Fluoroalcohol. Methacrylate and maleimide were randomly copolymerized to give copolymers rich in methacrylate units with minimal amounts of maleimide–maleimide sequences. Their terpolymerization resulted in a BAB-r-C sequence as a consequence of the selective BAB polymerization between limonene and maleimide, the random copolymerization between methacrylate and maleimide, and the lack of copolymerization between limonene and methacrylate.
-
renewable β methylstyrenes for bio based heat resistant styrenic copolymers radical copolymerization enhanced by Fluoroalcohol and controlled living copolymerization by raft
Polymer Chemistry, 2014Co-Authors: Yoshiki Nonoyama, Kotaro Satoh, Masami KamigaitoAbstract:Naturally occurring β-methylstyrenes, such as anethole (Ane), isosafrole (ISa), methyl isoeugenol (MIEu), and acetyl isoeugenol (AcIEu), which are phenylpropanoids and possess electron-donating alkoxy substituents on an aromatic ring, were copolymerized with common acrylic monomers, such as methyl (MA), n-butyl (nBA), and tert-butyl acrylates (tBA), N,N-dimethylacrylamide and diethyl fumarate in toluene and Fluoroalcohols. The copolymerizations of β-methylstyrenes (M1) and acrylic monomers (M2) were fitted well by the chain-end model. The relative reactivity of β-methylstyrenes with the acrylic radicals (1/r2) was enhanced up to 3 times in m-C6H4[C(CF3)2OH]2 compared to toluene, whereas no homo-propagation of β-methylstyrenes occurred in any solvent (r1 ∼ 0) because of the sterically hindered 1,2-disubstituted vinyl structure of β-methylstyrenes. The copolymerizability was also dependent on the substituents of both monomers: the relative reactivity of the β-methylstyrenes generally increased with the decreasing bulkiness of both β-methylstyrenes [1/r2 = 1/1.07 (AcIEu/MA), 1/0.62 (MIEu/MA), 1/0.53 (ISa/MA), 1/0.46 (Ane/MA)] (bulkiness: AcIEu > MIEu > Isa > Ane) and acrylates [1/r2 = 1/0.87 (Ane/tBA), 1/0.67 (Ane/nBA), 1/0.46 (Ane/MA)] (bulkiness: tBA > nBA > MA). The reversible addition–fragmentation chain-transfer copolymerization of Ane or ISa with MA proceeded in both toluene and m-C6H4[C(CF3)2OH]2, allowing molecular weight control of the copolymers. The incorporation of β-methylstyrene units into the copolymers was thus increased up to ∼45 mol% (∼60 wt%) by Fluoroalcohol, resulting in high-performance polymers with relatively high glass transition temperatures (Tg > 100 °C), even when using common alkyl acrylates as the comonomers.
-
aab sequence living radical chain copolymerization of naturally occurring limonene with maleimide an end to end sequence regulated copolymer
Journal of the American Chemical Society, 2010Co-Authors: Kotaro Satoh, Masaru Matsuda, Kanji Nagai, Masami KamigaitoAbstract:Sequence control in chain-growth polymerization is still one of the most challenging topics in synthetic polymer chemistry in contrast to natural macromolecules with completely sequence-regulated structures like proteins and DNA. Here, we report the quantitative and highly selective 1:2 sequence-regulated radical copolymerization of naturally occurring (+)-d-limonene (L) and a maleimide (M) in Fluoroalcohol giving chiral copolymers with high glass transition temperatures (220−250 °C) originating from the specific rigid cyclic structures of the monomers. Furthermore, the combination with a reversible addition−fragmentation chain transfer (RAFT) agent (C−S) via the controlled/living radical polymerization resulted in end-to-end sequence-regulated copolymers [C-(M-M-L)n-M-S] with both highly sequenced chain ends and main-chain repeating units as well as controlled molecular weights.
-
mn2 co 10 induced controlled living radical copolymerization of methyl acrylate and 1 hexene in Fluoroalcohol high α olefin content copolymers with controlled molecular weights
Macromolecules, 2009Co-Authors: Kazuhiko Koumura, Kotaro Satoh, Masami KamigaitoAbstract:A highly active manganese complex [Mn2(CO)10] efficiently induced the controlled/living radical copolymerizations of a conjugated polar vinyl monomer, methyl acrylate (MA), and an unconjugated nonpolar olefin, 1-hexene (1-Hex), in the presence of ethyl 2-iodoisobutyrate (EMA−I) as an initiator under weak visible light at 40 °C to give the copolymers with controlled molecular weights. The further use of protic Fluoroalcohols as solvents enhanced the copolymerization without losing the molecular weight control to result in a high 1-Hex content up to 50 mol %, for which the predominant alternating sequences were confirmed by the 13C NMR analysis of the copolymers. The kinetic analysis of the copolymerizations revealed an increase in the reactivity of the MA-radical to the 1-Hex monomer in the Fluoroalcohol [1/rMA = 0.49 in (CF3)2CHOH vs 0.081 in toluene], which can be attributed to the 1:1 hydrogen-bonding interaction between the MA unit and the Fluoroalcohol as suggested by the 13C NMR analysis of the MA−fl...
-
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...
Atsushi Takahara - One of the best experts on this subject based on the ideXlab platform.
-
direct controlled polymerization of ionic monomers by surface initiated atrp using a Fluoroalcohol and ionic liquids
Israel Journal of Chemistry, 2012Co-Authors: Motoyasu Kobayashi, Masami Terada, Yuki Terayama, Moriya Kikuchi, Atsushi TakaharaAbstract:Surface-initiated atom transfer radical polymerization (ATRP) of (2-methacryloyloxyethyl)trimethylammonium chloride (MTAC), 3-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatopropanesulfonate) (MAPS), and 2-methacryloyloxyethyl phosphorylcholine (MPC) was carried out in 2,2,2-trifluoroethanol (TFE) containing a small amount of 1-hexyl-3-methylimidazolium chloride at 60 °C to produce well-defined ionic polymer brushes and the corresponding free polymers with predictable number-average molecular weight (Mn, 1×104−3×105 g mol−1) and narrow molecular weight dispersity (Mw/Mn<1.2). A first-order kinetic plot for ATRP of MTAC and MAPS revealed a linear relationship between the monomer conversion index (ln([M]0/[M])) and polymerization time. Reduction in polymerization rates was observed with an increase in ionic liquid concentration. The Mn of both poly(MTAC) and poly(MAPS) increased in proportion to the conversion. The sequential polymerization of MAPS initiated with the chain ends of poly(MAPS) produced the postpolymer with quantitative efficiency. The thickness of the polymer brush was controllable from 5 to 100 nm based on the Mn of the polymer. These results suggest the successful control of the polymerization of sulfobetaine-type methacrylates owing to the TFE and ionic liquids. In particular, the high affinity of TFE for the sulfobetaine monomers and polymers yielded a homogeneous polymerization media to improve surface-initiated polymerization generating the polymer brushes on the substrate surface as well as the free polymers formed in the solution. The effect on ATRP of the chemical structure of ionic liquids and ligands for copper catalyst was also investigated.
-
well defined poly sulfobetaine brushes prepared by surface initiated atrp using a Fluoroalcohol and ionic liquids as the solvents
Macromolecules, 2011Co-Authors: Yuki Terayama, Motoyasu Kobayashi, Moriya Kikuchi, Atsushi TakaharaAbstract:Surface-initiated atom transfer radical polymerization (ATRP) of 2-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatoethanesulfonate) (MAES), 3-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatopropanesulfonate) (MAPS), and 4-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatobutanesulfonate) (MABS) was carried out in 2,2,2-trifluoroethanol (TFE) containing a small amount of 1-hexyl-3-methylimidazolium chloride at 60 °C to produce well-defined poly(sulfobetaine) brushes and the corresponding free polymers with predictable number-average molecular weight (Mn, 1 × 104 to 3 × 105 g mol−1) and narrow molecular weight distributions (Mw/Mn < 1.2). A first-order kinetic plot for ATRP of MAPS revealed a linear relationship between the monomer conversion index (ln([M]0/[M])) and polymerization time. The polymerization rates decreased with increasing ionic liquid concentration. The Mn of poly(MAPS) increased in proportion to the conversion. The sequential polymerization of MAPS initiated with the chain ends of poly(MAPS) ...
-
SURFACE-INITIATED ATRP OF IMIDAZOLIUM SALT- CONTAINING MONOMER IN Fluoroalcohol
2011Co-Authors: T. Ishikawa, M. Kikuchi, M. Kobayashi, Atsushi TakaharaAbstract:, indicating satisfactory control of the polymerization. The role of imidazolium ionic liquids in controlled polymerization of electrolyte monomers does not clarified, however, previous results suggested that the combination of TFE and imidazolium salts were effective to control the polymerization of methacrylate monomers bearing functional groups. Polymers bearing ionic liquid moieties are expected to be used as solidstate polymeric electrolytes and are of significant interest in the field of electrochemistry because they may avoid some disadvantages of liquid electrolytes, such as leakage and flammability, in the application areas of batteries and fuel cells. Therefore, synthesis of well-defined polymer brushes with ionic liquid moieties can be applied to precise surface modification utilizing characteristics of polyelectrolytes. In this study, SI-ATRP of MMA and methacrylate derivatives bearing imidazolium salt moiety in TFE and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) were demonstrated to understand the effect of imidazolium salt on the coppercatalyzed ATRP. Experimental Synthesis procedure of 1-(2-methacryloyloxy)ethyl-3-ethylimidazolium
-
direct synthesis of well defined poly 2 methacryloyloxy ethyl trimethylammonium chloride brush via surface initiated atom transfer radical polymerization in Fluoroalcohol
Macromolecules, 2010Co-Authors: Motoyasu Kobayashi, Masami Terada, Yuki Terayama, Moriya Kikuchi, Atsushi TakaharaAbstract:A well-defined cationic polymer and polymer brush were simultaneously prepared by copper-catalyzed atom transfer radical polymerization (ATRP) of 2-(methacryloxy)ethyltrimethylammonium chloride (MTAC) in 2,2,2-trifluoroethanol (TFE) at 60 °C initiated with ethyl 2-bromoisobutylate and the corresponding alkylbromide immobilized on silicon wafer. ATRP of MTAC in TFE as well as aqueous solution proceeded quickly but in a poorly controlled manner, leading to a relatively higher molecular weight distribution (MWD) than Mw/Mn = 1.3, where Mw and Mn are weight-average and number-average molecular weights, respectively. Addition of a small amount of isopropyl alcohol to the TFE-based reaction mixture reduced the polymerization rate and produced a poly(MTAC) with predictable molecular weight and narrower MWD than 1.19. The Mn of poly(MTAC) was controllable in the range 104−105 g mol−1 based on the molar ratio of monomer and initiator in the feed. The Mn of the brush on a flat silicon wafer matched that of the free...