• YAKHAK HOEJI
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• v.33 no.5
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• pp.296-299
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• 1989

The synthetic study of 2', 3'-diazido and difluoro secouridines toward development of new antiviral agents is discribed. These acyclic nucleosides were synthesized from uridine by the method of ring opening reaction of sugar moiety.

• Polymer(Korea)
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• v.34 no.6
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• pp.574-578
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• 2010

In this study, the caprolactone modified hydroxy acrylates (CHAs) were synthesized by ring-opening reaction of caprolactone and 2-hydroxyethyl acrylate (2-HEA) as initiator. Also, the caprolactone modified urethane acrylate (UA) oligomers were synthesized by condensation reaction of previously synthesized CHAs, 2-hydroxyethyl acrylate (2-HEA) and hexamethylene diisocyanate trimer (HDT). Using the hydroxy number of CHAs, the molecular weights of the CHAs were calculated easily and their molecular weight was similar to the theoretical molecular weight of them. The viscosity of UA oligomers decreased as increasing a content of CHA in the UA oligomer. Cure films were prepared from UA oligomer, reactive diluents, and UV initiator to investigate their physical properties. The thermal stability and color difference on high temperature for the cured film were improved as increasing the crosslinking density. Their surface hardness was also increased as increasing crosslinking density of the cured films, but their elongation at break was decreased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.417-421
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• 2005

Novel two synthetic technics using cationic ring-opening copolymerization of tetrahydrofuran (THF) and ethylene oxide (EO), or just polymerized EO on Poly-THF, could lead to random hydroxyl-terminated poly(EO-ran-THF) or tri-block PEG-PTHF-PEC, respectively. These reactions were carried out using $BF_3O(C_2H_5)_2$ as catalyst, 1,4-butanediol or PTHF as diol initiator. Copolymer structures were controlled by monomer feed ratio, or initial PTHF and EO monomer added amount. The molecular weight of polymer was merely dependant on the ratio of [monomer]/[diol], but not on catalyst. Well-defined random and block hydroxyl-terminated copolyether was found to be as the prepolymer for the propellant binder from the experiment to polyurethane with them.

• Polymer(Korea)
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• v.37 no.3
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• pp.332-341
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• 2013

H-shaped amphiphilic pentablock copolymers $(PSt)_2-b-PCL-b-PEO-b-PCL-b-(PSt)_2$ was synthesized via chemoenzymatic method by combining enzyme-catalyzed ring-opening polymerization (eROP) of ${\varepsilon}$-caprolactone (${\varepsilon}$-CL) and atom transfer radical polymerization (ATRP) of styrene. By this process, we obtained copolymers with controlled molecular weight and low polydispersity. The structure and composition of the obtained copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and infrared spectroscopy analysis (IR). The crystallization behavior of the copolymers was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The crystallization behavior of the H-shaped block copolymers demonstrated a PCL dominate crystallization. The self-assembly behavior of the copolymers was investigated in aqueous media. The hydrodynamic diameters of the copolymer micelles in aqueous solution were measured by dynamic light scattering (DLS). The morphology of the copolymer micelles was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The hydrodynamic diameters of spherical micelles declined gradually with the increase of the hydrophobic chain lengths of the copolymers. The critical micelle concentration (CMC) values were determined from fluorescence emission, and it was found that the CMCs decreased with an increase of PSt hydrophobic block lengths.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.228-235
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• 2009

We synthesized glycidyl azide monomer(GAM) as a monomer for polymerization of glycidy azide polymer(GAP) which is a promising energetic prepolymer for a plastic-bonded explosive. Using quantitative real-tim in-situ infrared(in-situ IR) spectroscopy, kinetic study on the cationic ring opening polymerization of GAM was carried out. The reaction rate was obtained from monitoring the change of ether C-O stretching band($1050cm^{-1}$) in series IR spectra. The reaction was in accordance with the first-order reaction law for each of reaction temperature at 100/1 mole ratio of [GAM]/[$BF_3*etherate$]. In the ring opening polymerization of GAM, with ratio of [GAM]/[$BF_3*etherate$] to equal 100/1 at various temperature, the activation parameters obtained from the evaluation of kinetic data were ${\Delta}H^*$=14.34kcal/mol, ${\Delta}S^*=-12.31cal/mol{\cdot}K$ and $E_a$=14.89kcal/mol.

• Membrane Journal
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• v.28 no.3
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• pp.169-179
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• 2018

The purposes of this paper were to improve both fouling and chlorine resistance by increasing the hydrophilicity of the reverse osmosis membrane. In order to improve chlorine resistance, the surface of RO membrane was activated by ultraviolet irradiation, and then it was modified by the sol-gel method using Octyltriethoxysilane (OcTES) such as the silane coupling agent to low sensitivity to chlorine, thereby the polyamide active layer was protected and chlorine resistance was improved. In addition, polyglycerol polyglycidyl ether (PGPE) and sorbitol polyglycidyl ether (SPE) coating with different number of epoxides, ring opening reaction of epoxide improved the anti-fouling resistance. The surface modification condition was optimized by FT-IR, XPS, and contact angle analysis. As a result, the permeability reduction rate of the silane-epoxy modified membrane after the fouling test was decreased about 1.5 times as compared with that of the commercial membrane. And the salt rejection was maintained over 90% at $20,000ppm{\times}hr$ even after chlorine resistance test.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.490-494
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• 2016

This paper describes the very efficient and highly enantioselective ring opening of terminal epoxides with alkyl and arene sulfonic acid. The dinuclear chiral (salen) Co complexes bearing Lewis acids of Al, Ga and In catalyze the reaction enantioselectively in the presence of tetrabutylammonium chloride using tert-butyl methyl ether as a solvent. The variation of the anion of the tetra butyl ammonium salt has significant impact on the reactivity and selectivity of the asymmetric ring opening of phenyl glycidyl ether with p-toluenesulfonic acid. The order of reactivity and selectivity was found to be $Cl^-$ > $l^-$ > $Br^-$ > $OH^-$. Strong synergistic effects of the different Lewis acid centers of Co-Al, Co-Ga and Co-In complexes were observed in the catalytic process. The dinuclear chiral salen catalyst containing $AlCl_3$ was found to be most active and highly enantioselective (91% ee).

• Clean Technology
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• v.17 no.4
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• pp.325-328
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• 2011

Atom-efficient preparation of 9, 9'-bis[4-(2'-hydroxy-3'-acryloyloxypropoxy) phenyl]fluorene (3), the extensively used building block for fluorene-containing acrylic epoxy polymers has been described. The epoxide ring opening esterification of 9, 9-bis[4-(glycidyloxy)phenyl]fluorene (1) with acrylic acid was catalyzed by some onium salts such as quaternary ammonium and phosphonium salts. While the coupling reactions depend greatly on the kind of the onium salts, the reaction of 9, 9-bis[4-(glycidyloxy)phenyl]fluorene (1) with acrylic acid proceed most efficiently in the presence of a catalytic amount of tetrabutylphosphonium bromide at $110^{\circ}C$ with 90% yield. This reaction is a cleaner reaction that minimizes the use of reactants and the production of chemical wastes.

• Polymer(Korea)
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• v.37 no.5
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• pp.606-612
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• 2013

Glycidol-poly(lactide) (Gly-PLA) were synthesized via L-lactide ring opening polymerization with glycidol as an initiator and $Al(O-i-Pr)_3$ catalyst. The structure of Gly-PLA was analyzed and successfully confirmed by 1H NMR. The OH group of glycidol in Gly-PLA was absent according to the $^1H$ NMR analysis, indicating that the terminal OH group of glycidol successfully served as an initiator in the L-lactide polymerization. The solution and bulk polymerizations of L-lactide with glycidol were performed to examine the effect of L-lactide/glycidol molar ratio, polymerization temperature and time on the molecular characteristics of Gly-PLA. The conversion and molecular weight increased with an increase in L-lactide/glycidol molar ratio. Gly-PLA showed the bimodal type DSC curve. The low $T_m$ peak of low molecular weight reduced but the high $T_m$ peak of high molecular weight increased as L-lactide/glycidol molar ratio increased.

• Polymer(Korea)
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• v.38 no.6
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• pp.714-719
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• 2014

Bio-based nylon 6-morpholinone random copolymers were prepared by the anionic ring opening polymerization of ${\varepsilon}$-caprolactam and morpholinone, both of which were prepared from lysine and glucose, respectively. From this work, a new biomass based nylon 6 with improved hydrophilicity was prepared. Optimizing the polymerization condition, copolymer with a viscosity-average molecular weight of 30000 g/mol was prepared, with a yield of 80%. It was possible to improve the hydrophilicity of nylon 6 by its copolymerization with morpholinone. The prepared nylon 6-morpholinone random copolymers were then characterized using several analytical methods such as DSC, TGA, XRD, viscosity measurement with U-shaped glass capillary viscometer and contact angle measurement.