• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.58-59
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• 2006

Less than a decade ago, most alternate membrane materials for fuel cells relied upon a post-sulfonation process to generate ionic groups capable of transporting protons from the anode to the cathode. These random post sulfonations showed some promise, but in general they produced materials that were not sufficiently stable or protonically conductive at ion exchange capacities where aqueous swelling could be restricted. Our group began to synthesize disulfonated monomers that could be used to incorporate into random copolymer proton exchange membranes. The expected limitation was that the aromatic polymers might not be stable enough to withstand fuel cell conditions. However, this was mostly based upon an accelerated test known was the Fenton's Reagent Test, which did not seem to this author as being a reliable predictor of performance. A much better approach has been to evaluate the open circuit voltage (OCV) for alternate membranes, as well as the benchmark perfluorosulfonic acid systems. When this is done, the aromatic ionomers of this study, primarily based upon disulfonated polyarylene ether sulfones, show up quite well. Real time 3000 hours DMFC results have also been generated. Obtaining conductive materials at low humidities is another major issue where alternate membranes have not been particularly successful. In order to address this problem, multiblock copolymers with relatively high water diffusion coefficients have been designed, which show promise for conductivity at lowered humidity.

• Korean Chemical Engineering Research
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• 제61권1호
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• pp.26-31
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• 2023

고분자 전해질 연료전지(Polymer electrolyte membrane fuel cell, PEMFC) 고분자막의 내구성 향상을 위해서 빠른 시간에 내구성을 평가할 수 있는 가속 내구 평가법들이 연구 개발되었다. 그러나 트럭, 버스 등 대형 상용차용 연료전지 수명은 승용차보다 3배 이상 요구되어 화학적 가속 내구 평가(Accelerated stress test, AST) 시간도 길어져서 1,500 시간 이상이 되었다. 그래서 본 연구에서는 단 시간내에 고분자막의 화학적 내구성을 평가하기 위한 방법으로 막 초기 특성으로 내구성을 예측할 수 있을지 검토하였다. 초기 특성으로 수소투과전류밀도(Hydrogen crossover current density, HCCD)와 단락 저항(Short resistance, SR)을 그리고 3시간의 셀 밖 실험으로 가능한 Fenton 실험을 통해 AST 시간을 예측하였다. HCCD와 불소 이온 유출 농도가 증가하면 AST 시간이 선형적으로 짧아지는 경향을 보였으나 편차가 있었다(R² ≒0.65). SR이 감소하면 AST 시간이 선형적으로 증가하는 상관관계를 보였으며 정확도가 높아(R² =0.93) 고분 자막 초기 SR로 AST 시간을 예측할 수 있었다.

• 한국수소및신에너지학회논문집
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• 제28권4호
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• pp.338-344
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• 2017

Polyoxometal molybdophosphoric acid (MoPA) bonded polyether ether ketone (PEEK) composite membrane for water electrolysis has been investigated. The composited membrane, covalently cross linked (CL) sulfonated polyether ether ketone (SPEEK) with a bonded MoPA, was prepared in sulfonation of PEEK, cross linkage reaction with 1,4-diiodobutane, and addition with MoPA. PEEK was covalently cross-linked with 1,4-diiodobutane to improve mechanical strength and was added with MoPA to increase proton conductivity. MoPA should be fixed to back bone of SPEEK to prevent bleeding out. Therefore, the carbonyl group of SPEEK was reduced with NaBH4 and 3-isocyanatepropyltriethoxysilane (ICPTES) was added. The MoPA bonded composite was produced in the reaction of MoPA with 3-mercaptopropyltrimethoxvsilane (MPTMS). In conclusion, MoPA bonded CL-SPEEK composite membrane featured 0.129 S/cm of proton conductivity at $80^{\circ}C$, and 2,156 hours of chemical stability in Fenton test. These properties are better than those of membranes of other SPEEK system.

• 한국수소및신에너지학회논문집
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• 제29권4호
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• pp.331-338
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• 2018

In this study, sulfonated PAES block copolymers have been synthesized via nucleophilic substitution reaction. Hydrophobic oligomer was prepared using 2,6-dihydroxynaphthalene and bis(4-chlorophenyl) sulfone, whereas hydrophilic oligomer was prepared using sulfonated bis(4-chlorophenyl) sulfone and bis(4-hydroxyphenyl) sulfone. The chemical structure of polymers was analyzed by $^1H$ NMR, FT-IR and GPC. The thermal properties of polymers were measured by TGA and DSC. The oxidative stability of membranes was investigated by Fenton's test. Furthermore, the proton conductivity of membrane was found to be 26 mS/cm at $90^{\circ}C$. All physiochemical properties suggest that fabricated membrane have a great potential for applications in PEMFC.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.308-314
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• 2021

Chemical durability issue in polymer electrolyte membranes has been a challenge for the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). In this study, we proposed a manufacturing method of Nafion composite membrane containing a stable polyimide antioxidant to improve the chemical durability of the membrane. The thermal casting of the Nafion solution with poly (amic acid) induced polyimide reaction. We evaluated proton conductivity, oxidative stability with ex-situ Fenton's test, and fluoride ion emission to analyze the effect of polyimide antioxidants. We confirmed that incorporating the polyimide antioxidant improves the chemical durability of the Nafion membrane while maintaining inherent proton conductivity.

• 전기화학회지
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• 제17권1호
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• pp.44-48
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• 2014

양성자교환막연료전지에서 사용할 탄화수소계 전해질 막 (술폰산화 폴리아릴렌에테르설폰)의 산화안정성을 향상시키기 위하여 세륨이온이 도입된 전해질 복합막을 제조하였다. 세륨이온의 함유 농도에 따른 산화안정성의 변화를 관찰하였고, 함수율 및 수소이온전도도에 미치는 영향을 조사하였다. ICP 분석을 통해 세륨이온의 함침여부를 검증하였고, NMR 피크의 화학적 이동으로 금속이온과 술폰산 그룹과의 배위여부를 확인하였다. 세륨이온의 함량이 증가함에 따라 이온전도도 및 함수율은 감소하였으나, 산화안정성은 향상되었다. 특히, 과산화수소폭로 가속화장치를 이용하여, 기존의 펜톤산화실험에 비해 실제 연료전지운전과 매우 유사한 조건에서 전해질 막의 산화안정성을 평가하였다.

• Advances in Traditional Medicine
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• 제4권3호
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• pp.197-209
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• 2004

The study was aimed at evaluating the antioxidant and antimicrobial activities of methanol extract of Caesalpinia bonducella leaves (MECB) (Family: Caesalpiniaceae). The effect of MECB on antioxidant activity, reducing power, free radical scavenging (DPPH radical, nitric oxide radical, superoxide anion radical, hydroxyl radical and hydrogen peroxide radical scavenging), total phenolic content and antimicrobial activities were studied. The antioxidant activity of MECB increased in a dose dependent manner. About 50, 100, 250 and 500 g of MECB showed 53.4, 61.2, 69.1 and 76.2 % inhibition respectively on peroxidation of linoleic acid emulsion. Like antioxidant activity, the effect of MECB on reducing power increased in a dose dependent manner. The free radical scavenging activity of MECB was determined by DPPH radical scavenging method. The potency of this activity was increased with increased amount of extract. MECB was found to inhibit the nitric oxide radicals generated from sodium nitroprusside $(IC_{50}\;=\;102.8\;g/ml)$ whereas the $IC_{50}$ value of curcumin was 20.4 g/ml. Moreover, the MECB was found to scavenge the superoxide generated by photoreduction of Riboflavin. MECB was also found to inhibit the hydroxyl radical generated by Fenton reaction, where the $IC_{50}$ value is 104.17 g/ml compared with catechin 5 g/ml, which indicates the antioxidant activity of MECB. The MECB capable of scavenging hydrogen peroxide in a concentration-dependent manner. The amounts of total phenolic compounds were also determined. Antimicrobial activities of MECB were carried out using disc diffusion methods with five Gram positive, four Gram negative and four fungal species. The results obtained in the present study indicate that MECB leaves are potential source of natural antioxidant and antimicrobial agents.

• 멤브레인
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• 제27권2호
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• pp.182-188
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• 2017

본 연구에서는 고분자 전해질 연료전지(PEFC)의 전해질막의 화학적 안정성의 향상을 위하여 3-mercaptopropyl silica gel (3MPTSG)과 poly(arylene ether sulfone)(SPAES)을 이용하여 복합막을 제조하였다. 일반적으로 방향족 탄화수소계 고분자막은 전극 부분에서 발생한 라디컬에 의한 고분자 산화가 일어나 내구성이 감소하게 되는데 이는 대부분 주쇄에 포함된 에테르 기 부분의 취약성으로 발생한다. 본 연구에서는 이러한 라디칼에 의한 고분자 주쇄의 산화를 방지하기 위해 친수성의 무기물 입자를 도입하여 이온전도도 감소율을 최소화하고 산화안정성을 높이고자 하였다. 복합막들의 물성 및 전기화학적 특성을 평가하기 위해 접촉각, FT-IR, 이온전도도, 이온교환용량(IEC), 함수율, 열안정성 등을 수행하였다. 실리카의 함량이 0에서 0.5%까지 증가함에 따라 이온전도도 및 함수율은 각각 10% 감소한 0.076 S cm-1 및 16% 감소한 24.6 wt%이었으나, 산화안정성은 10% 향상되었다.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2023년도 임시총회 및 춘계학술대회
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• pp.54-54
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• 2023

Nypa fruticans Wurmb (N. fruticans) is a plant that belongs to Araceae and N. fruticans is mainly found in tropical mangrove systems. The parts (leaves, stems, and roots) of N. fruticans are traditionally used for asthma, sore throat, and liver disease. N. fruticans contains flavonoids and polyphenols, which are substances that have inhibitory effects on cancer and oxidant. In previous studies, some pharmaceutical effects of N. fruticans on melanogenesis and inflammation have been reported. The present study is conducted to investigate the effect of the ethyl acetate fraction of N. fruticans (ENF) on oxidative DNA damage and UVB-induced DNA damage. DNA damage response (DDR) pathway is important in research on cancer, apoptosis, and so on. DDR pathways are considered a crucial factor affecting the alleviation of cellular damage. ENF could reduce oxidative DNA damage derived from reactive oxygen species by the Fenton reaction. Also, ENF reduced the intensity of intracellular ROS in the live cell image by DCFDA assay. UVB is known to cause skin and cellular damage, then finally contribute to causing the formation of tumors. As for the strategies of reducing DNA damage by UVB, inhibition of p53, H2AX, and Chk2 can be important indexes to protect the human body from DNA damage. As a result of confirming the protective effect of ENF for UVB damage, MMPs significantly decreased, and the expression of apoptosis-related factors tended to decrease. In conclusion, ENF can provide protective effects against double-stranded DNA break (DSB) caused by oxidative DNA damage and UVB-induced DNA damage. These results are considered to be closely related to the protective effect against radicals based on catechin, epicatechin, and isoquercitrin contained in ENF. Based on these results, it is thought that additional mechanism studies for inhibiting cell damage are needed.

• 한국수소및신에너지학회논문집
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• 제22권1호
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• pp.1-12
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• 2011

To improve the mechanical properties, such as durabilities and antioxidative characteristics, the covalently cross-linked (CL-) SPEEK (sulfonated polyether ether ketone)/Cs-substituted HPA (heteropoly acid) organic-inorganic composite membranes (CL-SPEEK/Cs-HPAs), have been intensively investigated. The composite membrane were prepared by blending cesium-substituted HPAs (Cs-HPAs), including tungstophosphoric acid (TPA), molybdophosphoric acid (MoPA), and tungstosilicic acid (TSiA) with cross-linking agent content of 0.01 mL. And composite electrolytes composed of Cs-HPAs, prepared by immersion (imm.) and titration (titr.) methods to increase the stability of HPAs in water, were applied to polymer electrolyte membrane electrolysis (PEME). As a result, the proton conductivity of Cs-substituted composite membranes increased rapidly over $60^{\circ}C$ but mechanical properties, such as tensile strength, decreased in accordance with added Cs content. The bleeding-out of Cs-TPA membranes by titration method (50 vol.% Cs) decreased steadily to 2.15%. In the oxidative stability test by Fenton solution, the durability of membranes with Cs-HPA significantly increased. In case of CL-SPEEK/ Cs-TPA membrane, duration time increased more than 1200 hours. It is expected that even though CL-SPEEK/Cs-MoPA membrane shows the high proton conductivity, electrocatalytic activity and cell voltage of 1.80 V for water electrolysis, the CL-SPEEK/Cs-TPA (imm.) is more suitable as an alternative membrane in real system with the satisfactory proton conductivity, mechanical properties, anti-oxidative stability and cell voltage of 1.89 V.