• Journal of Adhesion and Interface
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• v.11 no.3
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• pp.100-105
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• 2010

In this study, polyurethane dispersion was prepared by polyester polyol, 4,4-dicyclohexylmethane diisocyanate ($H_{12}MDI$), dimethylolpropionic acid (DMPA), and monomeric diol. The effect of various monomeric diol, polyol/monomeric diol molar ratio and DMPA contents on the properties of polyurethane dispersion were investigated. As the molecular weight of monomeric diol and monomeric diol molar ratio increased, $T_g$ gradually increased. And when DMPA contents increased, also $T_g$ gradually increased. In the results of mechanical properties, when the molecular weight of monomeric diol, monomeric diol molar ratio of polyol/monomeric diol and DMPA contents increased, tensile strength was increased. Finally, optimum peel strength obtained when polyol/monomeric diol ratio was 8 : 2.

• Journal of the Korean Chemical Society
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• v.56 no.6
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• pp.720-724
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• 2012

Under pseudo-first order conditions, the monomeric species of Cr(VI) was found to be kinetically active in the absence of phenanthroline (phen) whereas in the phen-promoted path, the Cr(VI)-phen complex undergoes a nucleophilic attack by etane-1,2-diol to form a ternary complex which subsequently experience a redox decomposition leading to hydroxy ethanal and Cr(III)-phen complex. The effect of the cationic surfactant (CPC), anionic surfactant (SDS) and neutral surfactant (TX-100) on the unpromoted and phen-promoted path have been studied. Micellar effects have been explained by considering the preferential partitioning of reactants between the micellar and aqueous phase. Combination of TX-100 and phenanthroline will be the ideal for chromic acid oxidation of ethane-1,2-diol in aqueous media.

• Bulletin of the Korean Chemical Society
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• v.14 no.5
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• pp.557-561
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• 1993

The interaction of vanadium(V) with various a-hydroxycarboxylate ligands in aqueous solution at pH 3.2 have been studied by $^{51}V$ and $^{13}C$ NMR spectroscopies. From the results it is supposed that vanadates mainly form the octahedral complexes with lactate, 2-hydroxybutyrate, glycerate, and malate. While, vanadates form the trigonal-bipyramidal complexes with glycolate, tartarate, and 2-hydroxy-3-methylbutyrate, and tetrahedral complexes with pyruvate(diol), 2-hydroxyisobutyrate, and 2-hydroxy-3-methylbutyrate. The bipyramidal products are formed as monomeric compounds. The octahedral products are formed as dimeric compounds with no evidence for a significant proportion of the monomeric derivatives. The complexes are mainly formed through the coordination at the carboxylate and the 2-hydroxyl groups of the ligands.

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.218-226
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• 2007

The stereoselective synthesis of chiral terminal epoxides is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new dinuclear chiral Co (salen) complexes bearing gallium-, indium- and tallium-chloride have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of dinuclear complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides having ether or ester groups by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99% ee). The dimeric structured chiral salen showed remarkably enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues. The system described in this work is very efficient for the synthesis of chiral epoxide and 1,2-diol intermediates

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.330-336
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• 2007

In this study, new dinuclear chiral Co (salen) complexes bearing $BF_3$ have been synthesized and their properties as the asymmetric catalyst have been examined. The NMR, UV and ESCA analyses were performed to determine the structure of synthesized catalysts. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99 %ee). The dimeric structured chiral salen showed remakablely enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues, and in addition no racemization happened during the separation of product epoxides. The system described in this work is very efficient for the sinthesis of chiral epoxide and 1,2-diol intermediates.