The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Takaji Yasui - One of the best experts on this subject based on the ideXlab platform.
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Stereoselective isomerization of chiral cobalt(III) complexes
Polyhedron, 1994Co-Authors: Takaji Yasui, Hiroshi KawaguchiAbstract:Abstract The isomerization reactions among the geometrical isomers of chiral complexes, [Co(EDMA)2]+, [Co(ida)(EDMA)], and [Co(mida)(EDMA)], have been studied in a weakly basic aqueous solution. Some of the optical active isomers exhibited stereoselective isomerization without the loss of optical activity. It was suggested that the isomerization of the isomer with facially or meridionally chelated-ligands proceeded through the deprotonated five-coordinated intermediate formed by CoO bond-rupture in the conjugate-base form.
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circular dichroism spectrum of ci trans o co c s EDMA d1 2 containing chiral methylene formed by stereospecific deuteration
Bulletin of the Chemical Society of Japan, 1991Co-Authors: Takaji Yasui, Jinsai HidakaAbstract:Ci-trans(O)-[Co(C(S)-EDMA-d1)2]+ was prepared by way of the stereospecific deuteration of the facially coordinated EDMA (ethylenediamine-N-acetate) in (−)543CD-C2-trans(O)-[Co(EDMA)2]+. The vicinal CD spectrum due to the C(S)-EDMA-d1 in the Ci-trans(O) complex was investigated in connection with the D→H exchange in the ligands, suggesting a two-step mechanism.
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stereoselective isomerization and racemization of n methyliminodiacetato ethylenediamine n acetato cobalt iii co mida EDMA in a basic aqueous solution
Bulletin of the Chemical Society of Japan, 1990Co-Authors: Hiroshi Kawaguchi, Kenji Tsuji, Takaji YasuiAbstract:Isomerization reactions of four geometrical isomers (pink, violet, brown, and light-brown) of [Co(mida)(EDMA)] were studied in a basic aqueous solution. In a reaction of the (−)565CD-pink isomer, two isomers of (−)561CD-brown and racemic light-brown formed simultaneously. The light-brown isomer isomerized mainly to the brown isomer. In reactions of the (+)572CD-violet and (+)561CD-brown isomers, the formations of other isomers were not observed but the racemizations occurred. The racemization reaction of the (+)572CD-violet isomer proceeded at a considerable rate. These reactions are discussed in connection with those for the [Co(ida)(EDMA)] system.
Hiroshi Kawaguchi - One of the best experts on this subject based on the ideXlab platform.
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Stereoselective isomerization of chiral cobalt(III) complexes
Polyhedron, 1994Co-Authors: Takaji Yasui, Hiroshi KawaguchiAbstract:Abstract The isomerization reactions among the geometrical isomers of chiral complexes, [Co(EDMA)2]+, [Co(ida)(EDMA)], and [Co(mida)(EDMA)], have been studied in a weakly basic aqueous solution. Some of the optical active isomers exhibited stereoselective isomerization without the loss of optical activity. It was suggested that the isomerization of the isomer with facially or meridionally chelated-ligands proceeded through the deprotonated five-coordinated intermediate formed by CoO bond-rupture in the conjugate-base form.
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stereoselective isomerization and racemization of n methyliminodiacetato ethylenediamine n acetato cobalt iii co mida EDMA in a basic aqueous solution
Bulletin of the Chemical Society of Japan, 1990Co-Authors: Hiroshi Kawaguchi, Kenji Tsuji, Takaji YasuiAbstract:Isomerization reactions of four geometrical isomers (pink, violet, brown, and light-brown) of [Co(mida)(EDMA)] were studied in a basic aqueous solution. In a reaction of the (−)565CD-pink isomer, two isomers of (−)561CD-brown and racemic light-brown formed simultaneously. The light-brown isomer isomerized mainly to the brown isomer. In reactions of the (+)572CD-violet and (+)561CD-brown isomers, the formations of other isomers were not observed but the racemizations occurred. The racemization reaction of the (+)572CD-violet isomer proceeded at a considerable rate. These reactions are discussed in connection with those for the [Co(ida)(EDMA)] system.
Gengliang Yang - One of the best experts on this subject based on the ideXlab platform.
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the fabrication of monolithic capillary column based on poly bisphenol a epoxy vinyl ester resin co ethylene glycol dimethacrylate and its applications for the separation of small molecules in high performance liquid chromatography
Journal of Chromatography A, 2013Co-Authors: Lijuan Wang, Gengliang YangAbstract:Abstract A new polymeric monolith was synthesized in fused-silica capillary by in situ polymerization technique. In the polymerization, bisphenol A epoxy vinyl ester resin (VER) was used as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the crosslinking monomer, 1,4-butanediol, 1-propanol and water as the co-porogens, and azobisisobutyronitrile (AIBN) as the initiator. The conditions of polymerization have been optimized. Morphology of the prepared poly (VER-co-EDMA) monolith was investigated by the scanning electron microscopy (SEM); pore properties were assayed by mercury porosimetry and nitrogen adsorption. The optimized poly (VER-co-EDMA) monolith showed a uniform structure, good permeability and mechanical stability. Then, the column was used as the stationary phase of high performance liquid chromatography (HPLC) to separate the mixture of benzene derivatives. The best column efficiency achieved for phenol was 235 790 theoretical plates per meter. Baseline separations of benzene derivatives and halogenated benzene compounds under optimized isocratic mode conditions were achieved with high column efficiency. The column showed good reproducibility: the relative standard deviation (RSD) values based on the retention times (n = 3) for run-to-run, column-to-column and batch-to-batch were less than 0.98, 1.68, 5.48%, respectively. Compared with poly (BMA-co-EDMA) monolithic column, the proposed monolith exhibited more efficiency in the separation of small molecules.
Lai Nanju - One of the best experts on this subject based on the ideXlab platform.
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synthesis and properties of a water soluble am aa nvp EDMA tetra copolymer for oil displacement
Chemical Research and Application, 2014Co-Authors: Lai NanjuAbstract:Firstly,a functional monomer( EDMA) was prepared by ethylenediamine and maleic anhydride,and a water-soluble AM /AA / NVP / EDMA tetra-copolymer was polymerized by free radical polymerization using acrylamide( AM),acrylic acid( AA),functional monomer( EDMA),and N-vinyl pyrrolidone( NVP) as raw materials. AM / AA / NVP / EDMA copolymer was characterized by infrared( IR) spectroscopy and1H Nuclear Magnetic Resonance(1HNMR). Discussed the relationship of viscosity and concentration,the heat resistance,shearing resistance and the enhanced oil recovery( EOR) of the copolymer. It was found that under the same concentration of tetra-copolymer viscosity increasing more than HPAM; and the viscosity of 5000 mg·L-1AM / AA / NVP / EDMA was881. 0 mPa·s at high temperature 90℃. It was also found that when the shear rate is 500s-1the viscosity is 807mPa·s after 2 min sheared. Core flooding experiments show that the EOR of this copolymer was up to 17. 7% by 0. 3PV 0. 15wt% tetra-copolymer solution and later water flooding at 70℃.
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Synthesis and properties of a water-soluble AM/AA/NVP/EDMA Tetra-copolymer for oil displacement
Chemical Research and Application, 2014Co-Authors: Lai NanjuAbstract:Firstly,a functional monomer( EDMA) was prepared by ethylenediamine and maleic anhydride,and a water-soluble AM /AA / NVP / EDMA tetra-copolymer was polymerized by free radical polymerization using acrylamide( AM),acrylic acid( AA),functional monomer( EDMA),and N-vinyl pyrrolidone( NVP) as raw materials. AM / AA / NVP / EDMA copolymer was characterized by infrared( IR) spectroscopy and1H Nuclear Magnetic Resonance(1HNMR). Discussed the relationship of viscosity and concentration,the heat resistance,shearing resistance and the enhanced oil recovery( EOR) of the copolymer. It was found that under the same concentration of tetra-copolymer viscosity increasing more than HPAM; and the viscosity of 5000 mg·L-1AM / AA / NVP / EDMA was881. 0 mPa·s at high temperature 90℃. It was also found that when the shear rate is 500s-1the viscosity is 807mPa·s after 2 min sheared. Core flooding experiments show that the EOR of this copolymer was up to 17. 7% by 0. 3PV 0. 15wt% tetra-copolymer solution and later water flooding at 70℃.
Hiroyuki Aota - One of the best experts on this subject based on the ideXlab platform.
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Effect of primary polymer chain rigidity on intramolecular cyclization and intramolecular crosslinking in free‐radical crosslinking monomethacrylate/dimethacrylate copolymerizations
Journal of Applied Polymer Science, 2020Co-Authors: Jun-ichi Ikeda, Yasuhide Hasei, Yuduri Yasuda, Hiroyuki Aota, Akira MatsumotoAbstract:d-Bornyl methacrylate (BoMA) was chosen as a typical example of bulky monomethacrylate monomers, the polymerization of which led to the formation of a rigid polymer chain. To discuss the effect of primary polymer chain rigidity on intramolecular cyclization, we compared the solution copolymerization results of BoMA with 1 mol % ethylene dimethacrylate (EDMA; n = 1) and poly(ethylene glycol dimethacrylate) [CH2C(CH3)CO(OCH2CH2)nOCOC(CH3)CH2, n = 9 (PEGDMA-9)] with those of methyl methacrylate (MMA) with 1 mol % EDMA and PEGDMA-9; the dependence of the weight-average degree of polymerization on conversion for the former BoMA copolymerization systems was completely opposed to that for the latter MMA systems, and this was a reflection of a reduced occurrence of intramolecular cyclization caused by the rigidity of the primary polymer chain. The effect of primary polymer chain rigidity on intramolecular crosslinking was discussed through a comparison of both BoMA/EDMA and MMA/EDMA copolymerizations. The correlations of the intrinsic viscosity, root-mean-square (rms) radius of gyration, and second virial coefficient with the molecular weight were examined for both BoMA/EDMA (90/10) and MMA/EDMA (90/10) copolymerizations in a dilute solution because microgelation was observed in solution MMA/EDMA (90/10) copolymerization as a reflection of a locally extensive occurrence of intramolecular crosslinking. The logarithmic plots of both the intrinsic viscosity and rms radius of gyration versus the molecular weight for MMA/EDMA copolymerization were compared with those for the corresponding BoMA/EDMA copolymerizations. The second virial coefficients were greater than 10−5 mol cm3 g−2 for BoMA/EDMA copolymers, even when the conversion was very close to the gel point, whereas they were quite low, that is, less than 10−5 mol cm3 g−2, for an MMA/EDMA copolymer obtained at more than 15% conversion. These were ascribed to a suppressed occurrence of intramolecular crosslinking, a reflection of the lessened flexibility of the polymer main chain and a steric effect due to the bulky d-bornyl groups. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1086–1093, 2004
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Electron spin resonance spectroscopic studies on microheterogeneity of crosslinked polymers. IV. Correlation between void evaluation of crosslinked resin and microgelation in monomethacrylate/dimethacrylate copolymerizations
Journal of Applied Polymer Science, 2020Co-Authors: Akira Matsumoto, Kazuyoshi Nishizawa, Yukihiko Yamashita, Takehiko Morita, Hiroyuki AotaAbstract:Electron spin resonance spectroscopic studies on the microheterogeneity of crosslinked polymers were performed to ascertain the correlation of the void evaluation of monomethacrylate/dimethacrylate (DMA) cured resins with the microgel formation before gelation in their crosslinking copolymerizations. Lauryl methacrylate (LMA) was added to methyl MA (MMA)/ethylene DMA (EDMA) copolymerization because the addition of LMA reduces the occurrence of intramolecular crosslinking by the steric hindrance of bulky long-chain alkyl groups, leading to the formation of a less densely crosslinked microgel core and a less microheterogeneously crosslinked resin. Then MMA/vinyl laurate (VL)/EDMA terpolymerization was performed because the polymerizability of conjugated methacryloyl groups belonging to MMA and EDMA is markedly high compared with the unconjugated vinyloxycarbonyl group of VL. Thus, enhanced microheterogeneity for MMA/VL/EDMA terpolymerization would be induced as compared with MMA/EDMA copolymerization. Finally, allyl MA (AMA) and vinyl MA (VMA) crosslinkers were used in place of EDMA because in the polymerizations of AMA and VMA having two types of carbon–carbon double bonds of different reactivities there was no microgelation observed up to the gel-point conversion. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1187–1192, 2001
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Electron Spin Resonance Spectroscopic Pursuit of Network Formation Processes in Free-Radical Crosslinking Polymerizations I. Microscopic Environmental Evaluation around Copper(II) Tetraphenylporphyrin Spin Probe Incorporated into or Excluded from Pol
Polymer Journal, 1996Co-Authors: Hiroyuki Aota, Akira Matsumoto, Yasuyuki Sanai, Mikiharu KamachiAbstract:The microheterogeneous network formation processes in the free-radical copolymerization of methyl methacrylate (MMA) with ethylene dimethacrylate (EDMA) were pursued Electron spin resonance (ESR)-spectroscopically by using copper tetraphenylporphyrin (CuTPP) and copper methacryloyloxyphenyl triphenylporphyrin (CuMAOTPP) as spin probes. Thus, CuTPP could be a useful tool to evaluate the mobility of low-molecular-weight molecules in the gelled system. In the MMA-EDMA copolymerization containing CuMAOTPP, three types of CuTPP moieties existed in the polymerization solution as immobilized in the densely crosslinked network, incorporated into the loosely crosslinked network, and unreacted monomer; their proportion was estimated by a semi-quantitative spectral simulation. For example, in the MMA-EDMA (70:30)-CuMAOTPP terpolymerization in a dilution of 1/10 in benzene, 30% of CuMAOTPP was immobilized at 76% conversion by the densely crosslinked network or microgel, just like as in a frozen state, while no restricted mobility was observed for unreacted CuMAOTPP in spite of a complete loss of fluidity of the polymerization solution.
