Showing papers by "Shiro Kobayashi published in 1998"
TL;DR: In this paper, a highly regioselective oxidative coupling of 4-phenoxyphenol (PPL) catalyzed by tyrosinase model complexes, (hydrotris(3,5-diphenyl-l-pyrazolyl)borate) copper(II) chloride (Cu(tpzb)Cl) and (l,4,7-triisopropyl- l, 4, 7-triazacyclonononane) copper dichloride (cu(tacn)Cl 2 ),
Abstract: A highly regioselective oxidative coupling of 4-phenoxyphenol (PPL) catalyzed by tyrosinase model complexes, (hydrotris(3,5-diphenyl-l-pyrazolyl)borate) copper(II) chloride (Cu(tpzb)Cl) and (l,4,7-triisopropyl-l,4,7-triazacyclononane) copper(II) dichloride (Cu(tacn)Cl 2 ), is described. The polymerization of PPL oxidized by an equimolar of 2,2'-azobisisobutyronitrile in toluene, regarded as a model system of free phenoxy radical coupling, gave C-C coupling dimers besides C-0 coupling dimers at the initial polymerization stage and yielded the polymer having no melting point. However, the polymerization of PPL catalyzed by Cu(tpzb)Cl and Cu(tacn)Cl2 under dioxygen in toluene gave no C-C coupling dimers, and hence, yielded poly(l,4-phenylene oxide) showing crystallinity with melting points.
93 citations
TL;DR: A new method to determine directly and rapidly the degree of acetylation of chitin/chitosan was developed based on reactive pyrolysis-gas chromatography in the presence of an oxalic acid aqueous solution and observed values were in good agreement with those obtained by (1)H NMR and the other methods.
Abstract: A new method to determine directly and rapidly the degree of acetylation of chitin/chitosan was developed based on reactive pyrolysis-gas chromatography in the presence of an oxalic acid aqueous solution. The degree of acetylation was precisely evaluated on the basis of peak intensities of the characteristic products such as acetonitrile, acetic acid, and acetamide originating from the N-acetyl group of N-acetyl-d-glucosamine units of chitin/chitosan. The observed values were in good agreement with those obtained by (1)H NMR and the other methods. Moreover, the proposed technique was applicable to any kinds of chitin/chitosan samples over the whole range of acetylation including insoluble chitin/chitosan and perfectly acetylated artificial chitin having higher crystallinity to which (1)H NMR had been inapplicable.
91 citations
TL;DR: The relationship between the type of the solvent and the polymerization behavior was investigated and an immobilized lipase derived from Candida antarctica causes a much faster polymerization of the lactones than the powdery lipases.
Abstract: Enzymatic ring-opening polymerization of medium-size lactones, e-caprolactone (e-CL) and 6-valerolactone (δ-VL). was performed by using a lipase as a catalyst. For the polymerization of e-CL in bulk, a lipase derived from Pseudomonas fluorescens (lipase PF) showed the highest catalytic activity among the powdery lipases examined, i.e., the highest molecular weight was achieved by using lipase PF. The polymerization behavior depends on the lipase origin as well as on the polymerization condition. From 1 H and 13 C NMR analyses the polymer was found to possess one terminal carboxylic acid group and one hydroxyl group, 6-VL was enzymatically polymerized. yielding the corresponding polyester. The polymerization rate of δ-VL catalyzed by lipase PF is larger than that of e-CL. whereas the molecular weight of poly(6-VL) is lower than that of poly(e-CL) obtained under similar reaction conditions. These lactones were also enzymatically polymerized in organic solvents. The relationship between the type of the solvent and the polymerization behavior was investigated. An immobilized lipase derived from Candida antarctica causes a much faster polymerization of the lactones than the powdery lipases. The immobilized lipase can be reused as a catalyst for the polymerization of e-CL.
91 citations
TL;DR: Enzymatic ring-opening polymerization and copolymerization of a nine-membered lactone, 8-octanolide (8-OL), was performed in isooctane by using various lipases of different origin as catalyst, showing high catalytic activity toward the present polymerization.
Abstract: Enzymatic ring-opening polymerization and copolymerization of a nine-membered lactone, 8-octanolide (8-OL), was performed in isooctane by using various lipases of different origin as catalyst. The polymerization behavior greatly depended on the lipase origin. Candida antarctica and Pseudomonas cepacia lipases (lipases CA and PC, respectively) showed high catalytic activity toward the present polymerization. Pseudomonas fluorescens lipase (lipase PF) also catalyzed the polymerization of 8-OL. The polymerization catalyzed by lipase CA proceeded much faster than that using other lipases. In the polymerization using lipase PC at 75 °C for 240 h, the polymer with number-average molecular weight of 1.6 × 104 was obtained. 8-OL monomer was recovered unchanged in the polymerization without the enzyme. The initial rate of the polymerization of lactones in different ring size was determined in the presence of 1-octanol. In case of lipase PC or PF, the rate increased with increasing ring size, whereas there was a mi...
88 citations
TL;DR: In this article, the phenolic moiety is selectively reacted in the horseradish-catalyzed polymerization of 2-(4-hydroxyphenyl)ethyl methacrylate.
Abstract: It is found that the phenolic moiety is selectively reacted in the horseradish-catalyzed polymerization of 2-(4-hydroxyphenyl)ethyl methacrylate. The polymer was thermally cross-linked at a relatively low temperature. The resulting polymer posssessed a methacryloyl group in the side chain and hence, is expected to have various applications as a highly reactive polymer
84 citations
TL;DR: In this article, the results of an Enzymatic oxidative polymerization of 4-hydroxybenzoic acid derivatives using oxidoreductases has been carried out in an aqueous organic solvent at room temperature under air.
Abstract: Enzymatic oxidative polymerization of 4-hydroxybenzoic acid derivatives using oxidoreductases has been carried out in an aqueous organic solvent at room temperature under air. The monomers used in this study were 4-hydroxybenzoic acid, 3,5-dimethoxy-4-hydroxybenzoic acid (syringic acid) and 3,5-dimethyl-4-hydroxybenzoic acid. The latter two monomers were subjected to oxidative polymerization using horseradish peroxidase (HRP), which involved elimination of carbon dioxide and hydrogen from the monomer to produce poly(1,4-oxyphenylene). Oxidoreductases, soybean and Coprinus cinerius peroxidases, Pycnoporus coccineus and Myceliophthore laccases, were active for the polymerization and the enzyme type and its origin greatly affected the polymerization behaviour. The effects of solvent composition have been systematically investigated with respect to polymer yield and molecular weight. In the case of HRP-catalysed polymerization of syringic acid, the highest molecular weight (1·5×104) was achieved in acetone/phosphate buffer (pH 7) (40: 60vol%). NMR, IR and matrix-assisted laser desorption/ionization–time of flight mass spectroscopic analyses of the polymer showed that the present polymer consisted made exclusively of 1,4-oxyphenylene unit and that the terminal structure was a carboxylic acid group at one end and a phenolic hydroxyl group at the other. © 1998 Society of Chemical Industry
75 citations
TL;DR: In vitro synthesis of aliphatic polyesters was achieved by lipase-catalysed polymerization of lactones, dicar☐ylic acid divinyl esters and glycols, in which two different types of polymerization—ring-opening polymerization and polycondensation—simultaneously occurred via the same acyl-lipase intermediate.
72 citations
TL;DR: In this article, a copper-containing oxidoreductase derived from Pycnoporus coccineus, induced the polymerization at relatively low temperature (50°C) to give a polymer of high molecular weight.
Abstract: Enzymatic polymerization of acrylamide was carried out in water. Laccase, a copper-containing oxidoreductase derived from Pycnoporus coccineus, induced the polymerization at relatively low temperature (50°C) to give a polymer of high molecular weight. In the presence of 2,4-pentanedione, laccase efficiently mediated the vinyl polymerization at room temperature.
58 citations
48 citations
TL;DR: In this article, a ring-opening polymerization of lactones using Candida antarctica lipase as catalyst to introduce the alcohol moiety at the polymer terminal (initiator method) was examined with respect to the molecular weight of the polymer and the introduced ratio of the alcohol mixture.
Abstract: Terminal-functionalized polyesters were synthesized by enzymatic ring-opening polymerization of lactones in the presence of a functional alcohol. The alcohol initiated the ring-opening polymerization of lactones using Candida antarctica lipase as catalyst to introduce the alcohol moiety at the polymer terminal (“initiator method”). Effects of the alcohol amount and monomer structure were examined with respect to the molecular weight of the polymer and the introduced ratio of the alcohol moiety by using 1-octanol initiator. ω-Unsaturated macromonomers were synthesized by using 5-hexen-1-ol or 5-hexyn-1-ol as initiator from 12-dodecanolide (DDL, 13-membered lactone), whereas the quantitative introduction of the alcohol was not achieved from e-caprolactone (7-membered lactone). In the polymerization of DDL employing 2-hydroxyethyl methacrylate as initiator, the methacryl group was quantitatively introduced at the polymer terminal to give the methacryltype polyester macromonomer.
47 citations
01 Jan 1998
TL;DR: In this paper, an enzymatic ring-opening polymerization of a 17-membered lactone, 16-hexadecanolide (HDL), was performed in bulk by using lipases of different origin as catalyst.
Abstract: Enzymatic ring-opening polymerization of a 17-membered lactone, 16-hexadecanolide (HDL), was performed in bulk by using lipases of different origin as catalyst. Pseudomonas fluorescens lipase exhibited high catalytic activity toward the polymerization, producing the corresponding polymer in high yields. A higher polymerization temperature (75°C) resulted in the formation of the polymer with molecular weight of more than 5×103. HDL monomer was recovered unchanged in the polymerization without the enzyme. Michaelis-Menten kinetics of lactones in five different ring size showed that HDL had the largest enzymatic polymerizability among the lactones examined.
TL;DR: Immobilized lipase derived from Candida antarctica is active in the polymerization of both monomers to give the corresponding aliphatic polyester having a hydroxy group at one end and a carboxylic acid group at the other.
Abstract: Lipase-catalyzed ring-opening polymerization of α-methyl-substituted medium-size lactones, α-methyl-δ-valerolactone and α-methyl-e-caprolactone, were carried in bulk Immobilized lipase derived from Candida antarctica is active in the polymerization of both monomers The polymerization proceeds under mild reaction conditions to give the corresponding aliphatic polyester having a hydroxy group at one end and a carboxylic acid group at the other
TL;DR: In this paper, the SBP-catalyzed polymerization of bisphenol-A was carried out in an aqueous organic solvent using horseradish and soybean peroxidases (HRP and SBP, respectively) as catalysts.
Abstract: Enzymatic oxidative polymerization of bisphenol-A was carried out in an aqueous organic solvent using horseradish and soybean peroxidases (HRP and SBP, respectively) as catalysts. The SBP-catalyzed polymerization in an equivolume mixture of methanol and phosphate buffer (pH 7.0) affords a new class of polyphenol quantitatively, which is readily soluble in polar organic solvents such as acetone, methanol, N,N-dimethylformamide, and dimethyl sulfoxide, but insoluble in chloroform, diethyl ether, and water. NMR and IR analyses show that the polymer is mainly composed of a mixture of phenylene and oxyphenylene units. The effects of the type of enzyme and the solvent composition were systematically investigated in respect to the yield and molecular weight of the polymer. The thermal treatment of the polymer produces an insoluble product and the curing temperature and the molecular weight of the starting polymer affect the thermal properties of the product. Crosslinking reaction of the present polyphenol with an epoxide resin affords insoluble polymeric material showing high thermal stability.
TL;DR: In this paper, the authors propose a method to improve the quality of the data collected by the data collection system of a data collection service. But, the results show that the system is ineffective.
Abstract: フッ化グリコシルを糖供与体とし、酵素触媒を用いる重縮合反応により、非天然型オリゴ糖を合成する手法を開発した。重縮合反応は完全に位置および立体選択的に進行するため、明確な構造を有するオリゴ糖の合成が可能である。得られたオリゴ糖は、糖水酸基の保護基を用いる従来の化学合成では合成困難なものばかりである。
TL;DR: In this article, a solvent-free polymerization of a dicarboxylic acid and glycol in a solvent free system, despite the heterogeneous mixture of the monomers and catalyst, was reported.
Abstract: Candida antarctica lipase induced polymerization of a dicarboxylic acid and glycol in a solvent-free system, despite the heterogeneous mixture of the monomers and catalyst. The chain length of the monomers strongly affected the yield and molecular weight of the product polyester.
TL;DR: In this paper, the effects of the concentration and molecular weight of the stabilizer on the particle size and size distribution have been investigated and the buffer pH and mixed ratio of the buffer and 1,4-dioxane also affected the particle formation.
Abstract: Preparation of polyphenol particles has been carried out by dispersion polymerization using horseradish peroxidase as catalyst in an aqueous 1,4-dioxane. The polymerization of phenol using poly(vinyl methyl ether) as steric stabilizer in 40% phosphate buffer (pH 7) solution afforded relatively monodisperse particles in the sub-micron range. Effects of the concentration and molecular weight of the stabilizer on the particle size and size distribution have been investigated. The buffer pH and mixed ratio of the buffer and 1,4-dioxane also affected the particle formation. From m- and p-cresols and p-phenylphenol, sub-micron size microspheres were obtained. The thermal treatment of the polyphenol particles at 1000°C under nitrogen afforded the particles of carbonized polymer.
TL;DR: In this article, the authors described the preparation of reactive monodisperse particles in the Micron range by Dispersion Polymerization of Glycidyl Methacrylate.
Abstract: Preparation of Reactive Monodisperse Particles in the Micron Range by Dispersion Polymerization of Glycidyl Methacrylate
TL;DR: In this article, a poly(phenylene oxide) copolymer with carboxylic acid at one end and a phenolic hydroxy group at the other using triphenylphosphine / hexachloroethane as coupling agent was shown to have relatively high thermal stability.
Abstract: Poly(phenylene oxide) (PPO) — aromatic polyester multiblock copolymers were synthesized by polycondensation of bisphenol-A / isophthalic acid or m- and p-hydroxybenzoic acids in the presence of PPO having a carboxylic acid at one end and a phenolic hydroxy group at the other using triphenylphosphine / hexachloroethane as coupling agent. TG analysis showed that the multiblock copolymer showed relatively high thermal stability.
TL;DR: In this paper, the in vitro synthesis of chitin via a nonbiosynthetic path has been achieved for the first time by enzymatic ring-opening polyaddition of a chitobiose oxazoline monomer (C20).
Abstract: The in vitro synthesis of chitin via a nonbiosynthetic path has been achieved for the first time by enzymatic ring-opening polyaddition of a chitobiose oxazoline monomer (C20). Chitinase, a hydrolysis enzyme of chitin, recognized and polymerized the monomer regio- and stereoselectively. The structure of artificial chitin was confirmed by comparison with an authentic natural chitin sample with the use of CP/MAS 13 C NMR and IR spectroscopy. X-ray diffraction as well as NMR analysis showed its crystal structure of α-chitin. Characteristic features of the present polymerization are described.
TL;DR: In this article, an immobilized lipase derived from Candida antarctica was used as catalyst for the ring opening polymerization of lactones, and a small amount of the immobilized enzyme showed the extremely efficient catalysis in the lactone polymerization.
Abstract: An immobilized lipase derived from Candida antarctica was used as catalyst for the ring opening polymerization of lactones. A small amount of the immobilized enzyme showed the extremely efficient catalysis in the lactone polymerization. The polymerization in the presence of 1-octanol enhanced the rate of reaction.
TL;DR: In this article, a seed dispersion polymerization of styrene in the presence of the seed particles produced monodisperse PMMA-polystyrene particles in the micron range.
Abstract: Seed dispersion polymerization of methyl methacrylate (MMA) in the presence of monodisperse PMMA particles was carried out in an aqueous methanol using poly(methacrylic acid) stabilizer. The polymerization using 2. 5 μ. m-sized seed particles gave monodisperse PMMA particles in the diameter up to 4. 9 μm. The solvent composition and monomer concentration greatly affected the polymerization behavior. Under appropriate conditions, monodisperse PMMA particles in the diameter up to 8. 9 μ, m was prepared from 4. 6 μm-sized seed particles. The seed dispersion polymerization of styrene in the presence of the seed particles produced monodisperse PMMA-polystyrene particles in the micron range. The particles were supposed to have a structure consisting of PMMA-core and polystyrene-shell from ESCA analysis.
TL;DR: In this paper, a novel germanium containing polymer, poly(germanium enolate), has been synthesized by the reaction of a divalent Germanium compound, germylene, with a cyclic α,β-unsaturated ketone in the presence of a catalytic amount of a lithium compound.
Abstract: A novel germanium containing polymer, poly(germanium enolate), has been synthesized by the reaction of a divalent germanium compound, germylene, with a cyclic α,β-unsaturated ketone in the presence of a catalytic amount of a lithium compound. The germylene was also copolymerized with a cyclic α,β-unsaturated lactone, affording an unstable polymer having a ketene acetal structure in the main chain. The resulting polymers are the first example having a metal enolate structure as repeating unit.