• Macromolecular Research
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• v.15 no.2
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• pp.160-166
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• 2007

Novel multiblock copolymers, based on segmented sulfonated hydrophilic-hydrophobic blocks, were synthesized and investigated for their application as proton exchange membranes. A series of segmented sulfonated poly(arylene ether sulfone)-b-polyimide multiblock copolymers, with various block lengths, were synthesized via the coupling reaction between the terminal amine moieties on the hydrophilic blocks and naphthalene anhydride functionalized hydrophobic blocks. Successful imidization reactions required a mixed solvent system, comprised of NMP and m-cresol, in the presence of catalysts. Proton conductivity measurements revealed that the proton conductivity improved with increasing hydrophilic and hydrophobic block lengths. The morphological structure of the multiblock copolymers was investigated using tapping mode atomic force microscopy (TM-AFM). The AFM images of the copolymers demonstrated well-defined nanophase separated morphologies, with the changes in the block length having a pronounced effect on the phase separated morphologies of the system. The self diffusion coefficient of water, as measured by $^1H$ NMR, provided a better understanding of the transport process. Thus, the block copolymers showed higher values than Nafion, and comparable proton conductivities in liquid water, as well as under partially hydrated conditions at $80^{\circ}C$. The new materials are strong candidates for use in PEM systems.

• Korean Membrane Journal
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• v.11 no.1
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• pp.1-7
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• 2009

This work reports the preparation of proton conductive crosslinked polymer electrolyte membranes by blending poly(vinyl chloride)-g-poly(hydroxyl ethyl acrylate) (PVC-g-PHEA) and poly(vinyl alcohol) (PVA). The PHEA chains of the graft copolymer were crosslinked with PVA using sulfosuccinic acid (SA) via the esterification reaction between -OH of polymer matrix and -COOH of SA. The PVC-g-PHEA graft copolymer was synthesized via atom transfer radical polymerization (ATRP) using direct initiation of the secondary chlorines of PVC backbones. Ion exchange capacity (IEC) continuously increased with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. However, the water uptake increased up to 20.0 wt% of SA concentration above which it decreased monotonically. The membrane exhibited a maximum proton conductivity of 0.026 S/cm at 20.0 wt% of SA concentration, which is presumably due to competitive effect between the increase of ionic sites and the crosslinking reaction.

• Korean Membrane Journal
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• v.9 no.1
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• pp.52-56
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• 2007

A proton exchange membrane was prepared by ${\gamma}-irradiation-induced$ grafting of styrene into poly(tetrafluoro-ethylene-co-perfluoropropyl vinyl ether) (PFA) and subsequent sulfonation reaction. The degree of grafting (DOG) increased with an increase in the absorbed dose. The prepared membranes showed high ion exchange capacity reaching 3.0 meq/g, which exceeded the performance of commercially available perfluorosulfonic acid membranes such as Nafion. The proton conductivity of PFA-g-PSSA membrane increased with the DOG and reached 0.17 S/cm for the highest sample at room temperature. The DMFC performance of the prepared membranes with 50% DOG was comparable to that of Nafion membrane.

• Membrane Journal
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• v.14 no.1
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• pp.44-52
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• 2004

This paper concerns the development of a cationic polymeric membranes for direct methanol fuel cell. The crosslinked poly(vinyl alcohol) (PVA) membranes with poly(acrylic acid-co-maleic acid) (PAM) and hydroquinonesulfonic acid (HQSA) as the crosslinking agents were prepared according to the amount of crosslinking agents. The resulting membranes were characterized in terms of methanol permeability, proton conductivity, water content and ion exchange capacity. The methanol permeability and proton conductivity increased with increasing PAM content up to 9 wt% and then decreased. This trend is considered the effect of the cross linking rather than the introduction of hydrophilic groups. When the HQSA contents were varied, no interesting increases of proton conductivity, water content and ion exchange capacity were found.

• Polymer(Korea)
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• v.34 no.2
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• pp.126-132
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• 2010

A cation-exchange nanofiber poly(vinylidene fluoride) (PVdF) membrane was prepared by a radiation-induced graft polymerization (RIGP) of sodium styrene sulfonate (NaSS) in the presence of the polymerizable access agents in methanol solution. The used polymerizable access agents include styrene, acrylic acid, and vinyl pyrrolidone. The anion-exchange nanofiber PVdF membrane was also prepared by RIGP of glycidyl methacrylate (GMA) and its subsequent chemical modification. The successful preparations of cation- and anion-exchange PVdF membranes were confirmed via SEM, XPS and thermal analysis. The content of the grafting yield, ion-exchange group, and water uptake was in the range of 30.0~32.3%, 2.81~3.01 mmol/g and 66.6~147%, respectively. The proton conductivity at 20$^{\circ}C$ was in the range of 0.020~0.053 S/cm. From the result, the prepared ionexchange PVdF membrane can be used as a separator in battery cells.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.167-172
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• 2009

Direct methanol fuel cells(DMFCs) are receiving significant attention in the portable power source and electric vehicular transportation because of its high energy efficiency as liquid fuel, low cost, and no requirement of fuel reforming process. In this study, we synthesized the Sulfonated poly(ether ether ketone) (SPEEK) to evaluate the possibility of use as a proton exchange membrane for DMFC. And poly(vinylidienedifluoride) (PVDF) was used to increase proton conductivity in SPEEK and simultaneously to prevent methanol transport through the cross linked membrane. Furthermore, in order to improve the electrical composite properties for DMFC applications.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1255-1257
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• 1997

In order to obtain key technologies for a kW class internal humidifying proton-exchange-membrane fuel cell (PEMFC) a single cell with a large electrode area has been designed and manufactured and the performance of large area membrane/electrode assemblies (MEAs) has been evaluated by using the single cell. A small area MEA made of commercial E-TEK electrode and Nafion 117 membrane showed a performance of 0.7V, $300mA/cm^2$ whereas large area MEA made of catalyst layer on carbon support and Nafion 117 showed a lower performance. To improve the performance of large MEA direct coating of catalyst was carried out on the membrane using a screen printer.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.11a
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• pp.61-63
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• 2003

A major research objective related to proton exchange membrane(PEM) for DMFC is to achieve high proton conductivity over 10$^{-2}$ S/cm, high hydrolytic stability and low methanol permeability with low cost base materials. for the purpose, a lot of thermoplastic polymers such as polysulfones, polyethersulfone, polyetherketones, polyimides, polyoxadiazole, polyphosphazene and polybenzimidazol have been investigated. Amongst those polymers, polyimides have been suggested as a potential PEM due to their excellent thermal, chemical stability and good mechanical properties. Generally, polyimides are synthesized by polycondensation with numerious diamines and dianhydriedes. In our study, polyimide was prepared using non-sulfonated diamine, sulfonated diamine directly synthesized by fuming sulfuric acid, and naphthalenic dianhydride to improve the hydrolysis stability under acidic condition. Through monomer sulfonation-subsequent polymerization method, the high proton conducting capability and the desired sulfonation level were effectively controlled at the same time. To reduce severe methanol transport through the membrane, the chemical crosslinking among polymer chains was introduced using various crosslinking agents with different chain lengths. The crosslinked sulfonated polyimide membranes showed high proton conductivity up to 8.09$\times$10$^{-2}$ S/cm and from crosslinking effect methanol transport through the membranes was considerably reduced as compared with unmodified membranes. For increase of chain length of crosslinker, methanol permeability was adversely reduced to 10$^{-8}$ $\textrm{cm}^2$/s due to decrease of IEC and increase of crosslinking desity.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.151-157
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• 2011

Crosslinked SPEEK/PVDF membrane were prepared by EB radiation method with various contents of PVDF. The prepared membranes were subjected to a comparative study of proton exchange membranes for fuel cell appreciations. The crosslinked SPEEK/PVDF membranes were characterized by using DMA, DSC and SAXS. The DMA data indicate that the ionic modulus values and cluster $T_g$ decrease with increasing PVDF content. Thus, it was suggested that the number of clustering in the crosslinked membranes can be reduced with increasing PVDF content. The DSC results were shown that the degree of crystalline of the membrane increased with increasing PVDF content. The morphology of the crosslinkied membranes was shown that with increasing PVDF content, the number of crystalline domain of the SPEEK/PVDF membranes increased but ionic aggregation of the membranes decreased. The water uptake behavior, ionic exchange capacity (IEC) and proton conductivity were decreased with increasing PVDF content. The overall findings suggest that the crosslinked membranes offer the possibility for improving the performance of PEMFC, provided that the membranes have thermal and hydration stability.

• Proceedings of the Membrane Society of Korea Conference
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• 2002.05a
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• pp.59-61
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• 2002

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