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Kwak N.-S.,Chungnam National University | Bae Sim J.,Aekyung Co. | Sun Koo J.,Chungnam National University | Sung Hwang T.,Chungnam National University | Tae Kim Y.,Korea Advanced Institute of Science and Technology
Journal of Membrane Science | Year: 2013

Novel ion-exchange membranes composed of dimethyl 5-sulfoisophthalate sodium salt (DMSIP), 1,6-hexanediol (HDO), isophthalic acid (IPA) and maleic anhydride (MA) were prepared by the synthesis of a DHIM oligomer and UV-cross-linking. The basic properties of the membranes were characterized, and a redox flow battery (RFB) test was conducted. The conversion and molecular weight of the DHIM oligomer decreased with increasing DMSIP contents; the maximum conversion and molecular weight values were 90.8% and 1335-1620g/mol, respectively. The thermal stability of the cross-linked DHIM ion-exchange membrane was 370°C. The water uptake and ion-exchange capacity increased as the DMSIP contents increased, and the maximum values were 43.1% and 1.23meq/g. The minimum values for the electrical resistance and ion transport were 0.27Ωcm2 and 0.998, respectively. Charge-discharge, voltage and energy efficiencies increased with the increasing extent of cross-linking, and their values were 90.81%, 79.92% and 71.52%, respectively. The minimum value of methanol permeability was lower than that of Nafion 117®, which indicates that the membrane has higher ion selectivity than Nafion 117®. © 2013. Source


Kwak N.-S.,Chungnam National University | Sim J.B.,Aekyung Co. | Hwang T.S.,Chungnam National University
Macromolecular Research | Year: 2013

Dimethyl 5-sulfoisophthalate sodium salt (DMSIP)-co-diethylene glycol (DEG)-co-maleic anhydride (MA)/phthalic anhydride (PA) oligomers were synthesized via condensation reaction and the corresponding membranes were prepared by UV curing. The number-average molecular weight (Mn) of the DMSIP-co-DEG-co-MA/PA (DDMP) was proportional to the concentration of DMSIP and ranged from 1,360-2,856 g/mol. A successful introduction of a -SO3Na group to the main oligomer chain was confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy and the thermal stability of the membranes up to 300 C was analyzed using thermogravimetric analysis (TGA). The water uptake values, swelling ratios, and the ion-exchange capacities of the membranes were 13%-30%, 7%-15%, and 0.7-0.9 meq/g, respectively. The electrical properties of the membrane, including the area resistance, ion transport number, and the cyclic charge-discharge current were also analyzed; these properties confirmed that these membranes were suitable for use in redox flow battery (RFB) applications. [Figure not available: see fulltext.] © 2013 The Polymer Society of Korea and Springer Sciene+Business Media Dordrecht. Source


Han D.-S.,Aekyung Co. | Han D.-S.,Korea Advanced Institute of Science and Technology | Kim Y.-M.,Aekyung Co. | Kim H.-Y.,Aekyung Co. | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

Quartz crystal microbalance with dissipation monitoring (QCM-D) was performed in order to study the adsorption behavior of monoelectrolytes (cationic surfactants: C12-16 trimethyl ammonium bromide) and polyelectrolytes (cationic starches and cationic alkyl substituted starches). An adsorption step using surfactant or polymer solutions and a desorption step of rinsing with distilled water were adopted in order to observe the adsorption behavior. The adsorbed amount of all cationic starches increased compared with that of the cationic surfactants, and the adsorption gap between the adsorption and desorption processes was remarkably small. In addition, a tendency for increased rigidity after desorption was observed. In particular, the cationic alkyl (C12-18) substituted starches had long alkyl chains as well as polymer backbones. In the results, the adsorbed layer of the cationic alkyl substituted starches increased more than the general cationic starches and exhibited more rigid properties. These results were attributed to the hydrophobic interactions among polymers originating from long alkyl chain substitutions. © 2013 Elsevier B.V. Source


Lee H.-S.,Aekyung Co. | Shin K.-H.,Aekyung Co. | Ryu G.-S.,Aekyung Co. | Cho I.-S.,Aekyung Co. | And 3 more authors.
Bulletin of the Korean Chemical Society | Year: 2013

Coumaroyl dipeptide amide, Coumaric acid-LG-NH2, was prepared successfully using the solid-phase method, and its efficacy as a skin whitening agent was studied. Coumaric acid-LG-NH2 was prepared with Rink-amide resin, and 96.354% of purity was obtained. Using MTT assay and LDH release assay, we found that it exhibited very low cytotoxicity. And, we found that Coumaric acid-LG-NH2 inhibited tyrosinase activity dose-dependently and showed superior tyrosinase inhibitory activity to well-known whitening agent, arbutin. IC50 value of Coumaric acid-LG-NH2 was 182.4 μM, and IC50 value of arbutin was 384.6 μM. Also, in measurement of melanin contents using B16F1 melanoma cell lines, Coumaric acid-LG-NH2 reduced melanin production induced by a-MSH statistically significant, and showed superior melanin inhibitory activity to p-coumaric acid or arbutin. In addition, Coumaric acid-LG-NH2 reduced MC1R mRNA expression level. Thus, we concluded that MC1R pathway is the significant pathway of Coumaric acid-LG-NH2, and Coumaric acid-LG-NH2 has great potential to be used as novel whitening agents. Source


Lee H.-S.,Aekyung Co. | Shin K.-H.,Aekyung Co. | Ryu G.-S.,Aekyung Co. | Chi G.-Y.,Aekyung Co. | And 2 more authors.
Bulletin of the Korean Chemical Society | Year: 2012

Small molecule conjugated peptides were prepared by solid-phase synthesis as potential novel whitening agents, and their melanogenesis inhibitory activities were investigated. The conjugated small molecules were well-known materials as tyrosinase inhibitors, and peptides were selected from the sequences that are known to antagonize melanocortin receptor 1 (MC1R). Most of small molecules-peptide conjugates showed superior melanin inhibition activity to kojic acid and arbutin. Among these, almost all compounds have -AR- sequence. From this study, we concluded that the small molecule conjugated peptides containing -AR- sequence have melanogenesis inhibitory activities and have potential to be used as novel whitening agents. Source

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