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Young Moo Lee - One of the best experts on this subject based on the ideXlab platform.
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Sulfonated poly(arylene ether sulfone)-silica nanocomposite membrane for direct Methanol fuel cell (DMFC)
Journal of Membrane Science, 2007Co-Authors: Chang Hyun Lee, Young Taik Hong, Kyung A. Min, Ho Bum Park, Byung Ok Jung, Young Moo LeeAbstract:Inorganic nanoparticles in nanocomposite membranes significantly affect the characteristics of those membranes, such as proton and Methanol Transport behavior, membrane durability, and electrochemical single cell result. Therefore, the inorganic nanoparticles should be deliberately chosen to fabricate composite membranes with desirable properties for DMFC. In this study, sulfonated poly(arylene ether sulfone) (SPAES) and hydrophilic fumed silica (SiO2) were used as a polymer matrix and an inorganic nanoparticle, respectively. The SiO2 nanoparticles have various surface areas (150, 200, 300, and 380 m 2 g −1 ) and average particle sizes (7, 12, and 14 nm). The SiO2 nanoparticles are evenly dispersed in the SPAES matrix by aid of a non-ionic surfactant (Pluronics ® L64). Interestingly, SiO2 particles with a high surface area and small particle size showed the best results: high proton conductivity, long membrane life time under oxidative conditions, good dimensional stability, outstanding single cell performance, and reduced Methanol crossover. Moreover, SiO2 content plays an important role in membrane microstructures and membrane properties such as proton conductivity and Methanol barrier behavior. An excessive SiO2 content caused a large aggregation of SiO2 particles, leading to the deterioration of mechanical properties in nanocomposite membranes. In the present study, optimal SiO2 content for maximizing the fuel cell performance of current nanocomposite membranes was ca. 2 wt.%. © 2007 Elsevier B.V. All rights reserved.
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preparation of organic inorganic nanocomposite membrane using a reactive polymeric dispersant and compatibilizer proton and Methanol Transport with respect to nano phase separated structure
Journal of Membrane Science, 2006Co-Authors: Juyoung Kim, Chang Hyun Lee, Ho Bum Park, Youn Suk Chung, Suresh Mulmi, Young Moo LeeAbstract:A poly(styrene–NaSS–UAN) random copolymer (PSSU) consisting of a sulfonated monomer (NaSS) and a non-sulfonated monomer (styrene) was successfully fabricated through a new copolymerization scheme using a urethane acrylate non-ionomer (UAN) as a compatibilizer to reduce solubility differences and enhance the miscibility of each monomer. The TEM image of the PSSU membranes showed that the nano-phase separated structure was comprised of hydrophilic domains dispersed within the hydrophobic polymer matrix along with a peculiar biphasic swelling behavior. UAN also played a role as a dispersant to uniformly distribute the silica nanoparticles of different hydrophilicity and to obtain subsequent sulfonated polystyrene–silica nanocomposite membranes. In the PSSU nanocomposite membranes, the use of hydrophilic silica nanoparticles improved both the hydrophilicity and Methanol barrier property of the membranes via a superior dispersion in the hydrophilic domains. Accordingly, it significantly contributed to an increase of the proton conductivity and a reduction of the Methanol permeability. On the other hand, hydrophobic silica nanoparticles, which were mainly dispersed in the hydrophobic domains, compensated for excessive water swelling with an increase in the content of ionic groups. The membrane performances in the fully hydrated state could be conveniently controlled through the direct incorporation of nano-sized silica particles using UAN.
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synthesis and characterization of sulfonated poly arylene ether sulfone copolymers containing carboxyl groups for direct Methanol fuel cells
Journal of Membrane Science, 2006Co-Authors: Dae Sik Kim, Ho Bum Park, Sang Yong Nam, Kwang Ho Shin, Youn Suk Chung, Young Moo LeeAbstract:Abstract Sulfonated poly(arylene ether sulfone) copolymers derived from sulfonated 4,4′-dichlorodiphenyl sulfone (S-DCDPS), 4,4′-dichlorodiphenyl sulfone (DCDPS) and phenolphthalin (PP) were evaluated as polymer electrolyte membranes for direct Methanol fuel cells. The change in ion exchange capacity, state of water content, proton conductivity, and Methanol permeability with S-DCDPS content are discussed. The proton conductivity increased linearly from 5.1 × 10 –3 to 4.7 × 10 –2 S cm −1 at 30 °C and 95% RH with increasing sulfonation level. However, the Methanol permeability increased linearly up to 20 mol% sulfonated monomer content, but then a sudden increase was observed, referred to as the “percolation threshold”, at sulfonated monomer content >20 mol%. The proton conductivity of the polymer membranes depended on the bound water and free water in the membrane, but their Methanol permeability depended on the free water content. The maximum selectivity (i.e. proton conductivity/Methanol permeability) of the membranes was obtained near the percolation concentration. The behavior of the proton and Methanol Transport mechanism is discussed in relation to the state of water in the membranes.
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annealing effect of sulfonated polysulfone ionomer membranes on proton conductivity and Methanol Transport
Journal of Membrane Science, 2005Co-Authors: Ho Bum Park, Young Moo Lee, Hyun Soo Shin, Ji Won RhimAbstract:Abstract Sulfonated polysulfone (SPSU) ionomer membranes were prepared via a solution sulfonation method using mixtures of chlorosulfonic acid (HSO 3 Cl) and chlorotrimethylsilane ((CH 3 ) 3 SiCl) as sulfonating agent. Ion exchange capacities (IECs) of SPSU ionomer membranes were controlled by varying the amount of HSO 3 Cl. In the present study, we investigated the thermal transition behavior of SPSU membranes annealed at different temperatures (60 and 150 °C) below glass transition temperature ( T g ) of SPSU ionomer membranes, and also studied the annealing effect on the proton conductivity and Methanol Transport through these ionomer membranes. The changes in T g (°C), ion exchange capacity (IEC, mmol/g), water uptake content (%), proton conductivity (S/cm), and Methanol permeability (cm 2 /s) were reported and discussed. The heat-treatment of SPSU membranes at higher temperature led to the increase in T g and simultaneously the decrease in water uptake, proton conductivity and Methanol permeability. Here, it was found that the annealing below T g accelerated the equilibrium process and physical aging of SPSU ionomer membranes and subsequently induced more compact chain packing structure, which eventually affected the proton and Methanol Transport through these ionomer membranes.
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proton conductivity and Methanol Transport behavior of cross linked pva paa silica hybrid membranes
Solid State Ionics, 2005Co-Authors: Dae Sik Kim, Ho Bum Park, Ji Won Rhim, Young Moo LeeAbstract:Abstract Cross-linked poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA)/silica hybrid membranes were prepared to evaluate the possibility of use as a proton exchange membrane for direct Methanol fuel cell (DMFC). A chemical cross-linking agent having sulfonic acid group (–SO3H) was used to increase proton conductivity, and simultaneously to prevent Methanol Transport through the cross-linked membranes. In addition, silica particles were dispersed into polymer matrices via sol–gel reaction under acidic conditions, expecting the barrier to the Methanol Transport. The proton and the Methanol Transport were investigated in terms of PVA/PAA compositions and cross-linker (sulfosuccinic acid, SSA) concentration. It was found that the compositions of PVA/PAA and the cross-linker concentration affected the Transport properties of the membranes. Particularly, the concentration of cross-linker markedly affected the proton and the Methanol Transport because SSA was used not only as a chemical cross-linker but also as a donor of fixed anionic group (–SO3−H+). The proton conductivities of the hybrid membrane were in the range of 10−3–10−2 S/cm, and the Methanol permeabilities ranged between 10−8 and 10−7 cm2/s. Noticeably, the Methanol permeabilities were reduced by cross-linking between PVA, PAA and SSA chains without a large sacrifice of proton conductivity. Moreover, the silica particles embedded in the cross-linked polymer membranes acted as a reducing material for fraction of free water as well as a Methanol barrier to hinder pathway from penetrating Methanol molecules.
Dae Sik Kim - One of the best experts on this subject based on the ideXlab platform.
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effect of organo clay content on proton conductivity and Methanol Transport through crosslinked pva hybrid membrane for direct Methanol fuel cell
Journal of Industrial and Engineering Chemistry, 2009Co-Authors: Dae Sik Kim, In Cheol Park, Hyun Il Cho, Dae Hoon Kim, Go Young Moon, Hyung Keun Lee, Ji Won RhimAbstract:Abstract In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared using poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA) (PVA:PSSA_MA = 1:7). The PSSA_MA was used both as a crosslinking agent and as a donor of the hydrophilic group (–SO3H and/or –COOH). The hybrid membranes were prepared by modified clay such as Clay Na+, Clay 30B, and Clay 15A. The thermal, water uptake, proton and Methanol Transport properties of the hybrid membrane were found to be sensitive to the clay type and content. The hybrid membrane with Clay 30B shows higher proton conductivity than other hybrid membranes due to hydroxyethyl group. The membrane with Clay 15A showed the lowest Methanol permeability due to lower specific gravity than other clay. Compared to the membrane without modified, the PVA/PSSA_MA/Clay 15A containing 4 wt% of Clay 15A showed both high proton conductivity (0.023 S/cm) and low Methanol permeability (2.19 × 10−7 cm2/s).
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comb shaped poly arylene ether sulfone s as proton exchange membranes
Macromolecules, 2008Co-Authors: Dae Sik Kim, Gilles P Robertson, Michael D. GuiverAbstract:A new sulfonated side-chain grafting unit containing two or four sulfonic acid groups was synthesized using sulfonated 4-fluorobenzophenone (FBP) and 1,1-bis(4-hydroxyphenyl)-1,4-((4-fluorophenyl)thio)phenyl-2,2,2-trifluoroethane (3FBPT). A conventional aromatic nucleophilic substitution (SNAr) was used for copolymerization of poly(arylene ether sulfone) containing a methoxy group. After converting the methoxy group to the reactive hydroxyl group, this functionalized copolymer was reacted to graft the sulfonated side chains to make the comb-shaped sulfonated poly(arylene ether sulfone) copolymers. All the polymers were characterized by 1H NMR, thermogravimetric analysis (TGA), the water uptake, and proton and Methanol Transport for fuel cell applications. These comb-shaped sulfonated polymers had good properties as polyelectrolyte membrane materials. The comb-shaped copolymers with two or four sulfonic acid groups show high proton conductivity in the range of 34−147 and 63−125 mS/cm, respectively. The met...
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preparation of ion exchange membranes for fuel cell based on crosslinked poly vinyl alcohol with poly styrene sulfonic acid co maleic acid
Journal of Membrane Science, 2006Co-Authors: Dae Sik Kim, Michael D. Guiver, Sang Yong Nam, Tae Il Yun, Mu Young Seo, Se Jin Kim, Ho Sang Hwang, Ji Won RhimAbstract:Crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at various crosslinking temperatures using poly(acrylic acid-co-maleic acid) (PAM) containing different PAM contents. The thermal properties of these PVA/PAM membranes prepared at various reaction temperatures were characterized using differential scanning calorimetry (DSC). The proton conductivity and Methanol permeability of PVA/PAM membranes were then investigated as PAM content was varied from 3 to 13 wt%. It was found that the proton and Methanol Transport were dependent on PAM content in their function both as crosslinking agent and as donor of hydrophilic -COOH groups. Both these properties decreased monotonously with increasing PAM concentration. The proton conductivities of these PVA/PAM membranes were in the range from 10−3 to 10−2S/cm and the Methanol permeabilities from 10−7 to 10−6cm2/sec. In addition, the effect of operating temperature up to 80 °C on ion conductivity was examined for three selected membranes: 7, 9 and 11 wt% PAM membranes. Ion conductivity increased with increasing operating temperature and showed and S/cm at 80 °C, respectively. The effects of crosslinking and ionomer group concentration were also examined in terms of water content, ion exchange capacity (IEC), and fixed ion concentration. In addition, the number of water molecules per ionomer site was calculated using both water contents and IEC values. With overall consideration for all the properties measured in this study, 7∼9 wt% PAM membrane prepared at 140 °C exhibited the best performance. These characteristics of PVA/PAM membranes are desirable in applications related to the direct Methanol fuel cell (DMFC).
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synthesis and characterization of sulfonated poly arylene ether sulfone copolymers containing carboxyl groups for direct Methanol fuel cells
Journal of Membrane Science, 2006Co-Authors: Dae Sik Kim, Ho Bum Park, Sang Yong Nam, Kwang Ho Shin, Youn Suk Chung, Young Moo LeeAbstract:Abstract Sulfonated poly(arylene ether sulfone) copolymers derived from sulfonated 4,4′-dichlorodiphenyl sulfone (S-DCDPS), 4,4′-dichlorodiphenyl sulfone (DCDPS) and phenolphthalin (PP) were evaluated as polymer electrolyte membranes for direct Methanol fuel cells. The change in ion exchange capacity, state of water content, proton conductivity, and Methanol permeability with S-DCDPS content are discussed. The proton conductivity increased linearly from 5.1 × 10 –3 to 4.7 × 10 –2 S cm −1 at 30 °C and 95% RH with increasing sulfonation level. However, the Methanol permeability increased linearly up to 20 mol% sulfonated monomer content, but then a sudden increase was observed, referred to as the “percolation threshold”, at sulfonated monomer content >20 mol%. The proton conductivity of the polymer membranes depended on the bound water and free water in the membrane, but their Methanol permeability depended on the free water content. The maximum selectivity (i.e. proton conductivity/Methanol permeability) of the membranes was obtained near the percolation concentration. The behavior of the proton and Methanol Transport mechanism is discussed in relation to the state of water in the membranes.
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proton conductivity and Methanol Transport behavior of cross linked pva paa silica hybrid membranes
Solid State Ionics, 2005Co-Authors: Dae Sik Kim, Ho Bum Park, Ji Won Rhim, Young Moo LeeAbstract:Abstract Cross-linked poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA)/silica hybrid membranes were prepared to evaluate the possibility of use as a proton exchange membrane for direct Methanol fuel cell (DMFC). A chemical cross-linking agent having sulfonic acid group (–SO3H) was used to increase proton conductivity, and simultaneously to prevent Methanol Transport through the cross-linked membranes. In addition, silica particles were dispersed into polymer matrices via sol–gel reaction under acidic conditions, expecting the barrier to the Methanol Transport. The proton and the Methanol Transport were investigated in terms of PVA/PAA compositions and cross-linker (sulfosuccinic acid, SSA) concentration. It was found that the compositions of PVA/PAA and the cross-linker concentration affected the Transport properties of the membranes. Particularly, the concentration of cross-linker markedly affected the proton and the Methanol Transport because SSA was used not only as a chemical cross-linker but also as a donor of fixed anionic group (–SO3−H+). The proton conductivities of the hybrid membrane were in the range of 10−3–10−2 S/cm, and the Methanol permeabilities ranged between 10−8 and 10−7 cm2/s. Noticeably, the Methanol permeabilities were reduced by cross-linking between PVA, PAA and SSA chains without a large sacrifice of proton conductivity. Moreover, the silica particles embedded in the cross-linked polymer membranes acted as a reducing material for fraction of free water as well as a Methanol barrier to hinder pathway from penetrating Methanol molecules.
Michael D. Guiver - One of the best experts on this subject based on the ideXlab platform.
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fluorene based poly arylene ether sulfone s containing clustered flexible pendant sulfonic acids as proton exchange membranes
Macromolecules, 2011Co-Authors: Chenyi Wang, Na Rae Kang, Dong-won Shin, Nanwen Li, Michael D. GuiverAbstract:A new bisphenol monomer, 9,9-bis(3,5-dimethoxy-4-hydroxyphenyl) fluorene, was synthesized and polymerized to form fluorene-based poly(arylene ether sulfone) copolymers containing tetra-methoxy groups (MPAES). After converting the methoxy group to the reactive hydroxyl group, the respective side-chain type sulfonated copolymers (SPAES) were obtained by sulfobutylation. The polymers were characterized by 1H NMR, thermogravimetric analysis (TGA), water uptake, and proton and Methanol Transport for fuel cell applications. These SPAES copolymers had good overall properties as polymer electrolyte membrane (PEM) materials, having high proton conductivity in the range of 0.061–0.209 and 0.146–0.365 S/cm at 30 and 80 °C (under hydrated conditions), respectively. SPAES-39 (IEC = 1.93 mequiv/g) showed higher or comparable proton conductivity than that of Nafion 117 at 50–95% RH (relative humidity). The Methanol permeabilities of these membranes were in the range of 3.22 to 13.1 × 10–7 cm2/s, which is lower than Nafi...
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comb shaped poly arylene ether sulfone s as proton exchange membranes
Macromolecules, 2008Co-Authors: Dae Sik Kim, Gilles P Robertson, Michael D. GuiverAbstract:A new sulfonated side-chain grafting unit containing two or four sulfonic acid groups was synthesized using sulfonated 4-fluorobenzophenone (FBP) and 1,1-bis(4-hydroxyphenyl)-1,4-((4-fluorophenyl)thio)phenyl-2,2,2-trifluoroethane (3FBPT). A conventional aromatic nucleophilic substitution (SNAr) was used for copolymerization of poly(arylene ether sulfone) containing a methoxy group. After converting the methoxy group to the reactive hydroxyl group, this functionalized copolymer was reacted to graft the sulfonated side chains to make the comb-shaped sulfonated poly(arylene ether sulfone) copolymers. All the polymers were characterized by 1H NMR, thermogravimetric analysis (TGA), the water uptake, and proton and Methanol Transport for fuel cell applications. These comb-shaped sulfonated polymers had good properties as polyelectrolyte membrane materials. The comb-shaped copolymers with two or four sulfonic acid groups show high proton conductivity in the range of 34−147 and 63−125 mS/cm, respectively. The met...
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preparation of ion exchange membranes for fuel cell based on crosslinked poly vinyl alcohol with poly styrene sulfonic acid co maleic acid
Journal of Membrane Science, 2006Co-Authors: Dae Sik Kim, Michael D. Guiver, Sang Yong Nam, Tae Il Yun, Mu Young Seo, Se Jin Kim, Ho Sang Hwang, Ji Won RhimAbstract:Crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at various crosslinking temperatures using poly(acrylic acid-co-maleic acid) (PAM) containing different PAM contents. The thermal properties of these PVA/PAM membranes prepared at various reaction temperatures were characterized using differential scanning calorimetry (DSC). The proton conductivity and Methanol permeability of PVA/PAM membranes were then investigated as PAM content was varied from 3 to 13 wt%. It was found that the proton and Methanol Transport were dependent on PAM content in their function both as crosslinking agent and as donor of hydrophilic -COOH groups. Both these properties decreased monotonously with increasing PAM concentration. The proton conductivities of these PVA/PAM membranes were in the range from 10−3 to 10−2S/cm and the Methanol permeabilities from 10−7 to 10−6cm2/sec. In addition, the effect of operating temperature up to 80 °C on ion conductivity was examined for three selected membranes: 7, 9 and 11 wt% PAM membranes. Ion conductivity increased with increasing operating temperature and showed and S/cm at 80 °C, respectively. The effects of crosslinking and ionomer group concentration were also examined in terms of water content, ion exchange capacity (IEC), and fixed ion concentration. In addition, the number of water molecules per ionomer site was calculated using both water contents and IEC values. With overall consideration for all the properties measured in this study, 7∼9 wt% PAM membrane prepared at 140 °C exhibited the best performance. These characteristics of PVA/PAM membranes are desirable in applications related to the direct Methanol fuel cell (DMFC).
Ho Bum Park - One of the best experts on this subject based on the ideXlab platform.
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Sulfonated poly(arylene ether sulfone)-silica nanocomposite membrane for direct Methanol fuel cell (DMFC)
Journal of Membrane Science, 2007Co-Authors: Chang Hyun Lee, Young Taik Hong, Kyung A. Min, Ho Bum Park, Byung Ok Jung, Young Moo LeeAbstract:Inorganic nanoparticles in nanocomposite membranes significantly affect the characteristics of those membranes, such as proton and Methanol Transport behavior, membrane durability, and electrochemical single cell result. Therefore, the inorganic nanoparticles should be deliberately chosen to fabricate composite membranes with desirable properties for DMFC. In this study, sulfonated poly(arylene ether sulfone) (SPAES) and hydrophilic fumed silica (SiO2) were used as a polymer matrix and an inorganic nanoparticle, respectively. The SiO2 nanoparticles have various surface areas (150, 200, 300, and 380 m 2 g −1 ) and average particle sizes (7, 12, and 14 nm). The SiO2 nanoparticles are evenly dispersed in the SPAES matrix by aid of a non-ionic surfactant (Pluronics ® L64). Interestingly, SiO2 particles with a high surface area and small particle size showed the best results: high proton conductivity, long membrane life time under oxidative conditions, good dimensional stability, outstanding single cell performance, and reduced Methanol crossover. Moreover, SiO2 content plays an important role in membrane microstructures and membrane properties such as proton conductivity and Methanol barrier behavior. An excessive SiO2 content caused a large aggregation of SiO2 particles, leading to the deterioration of mechanical properties in nanocomposite membranes. In the present study, optimal SiO2 content for maximizing the fuel cell performance of current nanocomposite membranes was ca. 2 wt.%. © 2007 Elsevier B.V. All rights reserved.
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preparation of organic inorganic nanocomposite membrane using a reactive polymeric dispersant and compatibilizer proton and Methanol Transport with respect to nano phase separated structure
Journal of Membrane Science, 2006Co-Authors: Juyoung Kim, Chang Hyun Lee, Ho Bum Park, Youn Suk Chung, Suresh Mulmi, Young Moo LeeAbstract:A poly(styrene–NaSS–UAN) random copolymer (PSSU) consisting of a sulfonated monomer (NaSS) and a non-sulfonated monomer (styrene) was successfully fabricated through a new copolymerization scheme using a urethane acrylate non-ionomer (UAN) as a compatibilizer to reduce solubility differences and enhance the miscibility of each monomer. The TEM image of the PSSU membranes showed that the nano-phase separated structure was comprised of hydrophilic domains dispersed within the hydrophobic polymer matrix along with a peculiar biphasic swelling behavior. UAN also played a role as a dispersant to uniformly distribute the silica nanoparticles of different hydrophilicity and to obtain subsequent sulfonated polystyrene–silica nanocomposite membranes. In the PSSU nanocomposite membranes, the use of hydrophilic silica nanoparticles improved both the hydrophilicity and Methanol barrier property of the membranes via a superior dispersion in the hydrophilic domains. Accordingly, it significantly contributed to an increase of the proton conductivity and a reduction of the Methanol permeability. On the other hand, hydrophobic silica nanoparticles, which were mainly dispersed in the hydrophobic domains, compensated for excessive water swelling with an increase in the content of ionic groups. The membrane performances in the fully hydrated state could be conveniently controlled through the direct incorporation of nano-sized silica particles using UAN.
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synthesis and characterization of sulfonated poly arylene ether sulfone copolymers containing carboxyl groups for direct Methanol fuel cells
Journal of Membrane Science, 2006Co-Authors: Dae Sik Kim, Ho Bum Park, Sang Yong Nam, Kwang Ho Shin, Youn Suk Chung, Young Moo LeeAbstract:Abstract Sulfonated poly(arylene ether sulfone) copolymers derived from sulfonated 4,4′-dichlorodiphenyl sulfone (S-DCDPS), 4,4′-dichlorodiphenyl sulfone (DCDPS) and phenolphthalin (PP) were evaluated as polymer electrolyte membranes for direct Methanol fuel cells. The change in ion exchange capacity, state of water content, proton conductivity, and Methanol permeability with S-DCDPS content are discussed. The proton conductivity increased linearly from 5.1 × 10 –3 to 4.7 × 10 –2 S cm −1 at 30 °C and 95% RH with increasing sulfonation level. However, the Methanol permeability increased linearly up to 20 mol% sulfonated monomer content, but then a sudden increase was observed, referred to as the “percolation threshold”, at sulfonated monomer content >20 mol%. The proton conductivity of the polymer membranes depended on the bound water and free water in the membrane, but their Methanol permeability depended on the free water content. The maximum selectivity (i.e. proton conductivity/Methanol permeability) of the membranes was obtained near the percolation concentration. The behavior of the proton and Methanol Transport mechanism is discussed in relation to the state of water in the membranes.
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annealing effect of sulfonated polysulfone ionomer membranes on proton conductivity and Methanol Transport
Journal of Membrane Science, 2005Co-Authors: Ho Bum Park, Young Moo Lee, Hyun Soo Shin, Ji Won RhimAbstract:Abstract Sulfonated polysulfone (SPSU) ionomer membranes were prepared via a solution sulfonation method using mixtures of chlorosulfonic acid (HSO 3 Cl) and chlorotrimethylsilane ((CH 3 ) 3 SiCl) as sulfonating agent. Ion exchange capacities (IECs) of SPSU ionomer membranes were controlled by varying the amount of HSO 3 Cl. In the present study, we investigated the thermal transition behavior of SPSU membranes annealed at different temperatures (60 and 150 °C) below glass transition temperature ( T g ) of SPSU ionomer membranes, and also studied the annealing effect on the proton conductivity and Methanol Transport through these ionomer membranes. The changes in T g (°C), ion exchange capacity (IEC, mmol/g), water uptake content (%), proton conductivity (S/cm), and Methanol permeability (cm 2 /s) were reported and discussed. The heat-treatment of SPSU membranes at higher temperature led to the increase in T g and simultaneously the decrease in water uptake, proton conductivity and Methanol permeability. Here, it was found that the annealing below T g accelerated the equilibrium process and physical aging of SPSU ionomer membranes and subsequently induced more compact chain packing structure, which eventually affected the proton and Methanol Transport through these ionomer membranes.
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proton conductivity and Methanol Transport behavior of cross linked pva paa silica hybrid membranes
Solid State Ionics, 2005Co-Authors: Dae Sik Kim, Ho Bum Park, Ji Won Rhim, Young Moo LeeAbstract:Abstract Cross-linked poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA)/silica hybrid membranes were prepared to evaluate the possibility of use as a proton exchange membrane for direct Methanol fuel cell (DMFC). A chemical cross-linking agent having sulfonic acid group (–SO3H) was used to increase proton conductivity, and simultaneously to prevent Methanol Transport through the cross-linked membranes. In addition, silica particles were dispersed into polymer matrices via sol–gel reaction under acidic conditions, expecting the barrier to the Methanol Transport. The proton and the Methanol Transport were investigated in terms of PVA/PAA compositions and cross-linker (sulfosuccinic acid, SSA) concentration. It was found that the compositions of PVA/PAA and the cross-linker concentration affected the Transport properties of the membranes. Particularly, the concentration of cross-linker markedly affected the proton and the Methanol Transport because SSA was used not only as a chemical cross-linker but also as a donor of fixed anionic group (–SO3−H+). The proton conductivities of the hybrid membrane were in the range of 10−3–10−2 S/cm, and the Methanol permeabilities ranged between 10−8 and 10−7 cm2/s. Noticeably, the Methanol permeabilities were reduced by cross-linking between PVA, PAA and SSA chains without a large sacrifice of proton conductivity. Moreover, the silica particles embedded in the cross-linked polymer membranes acted as a reducing material for fraction of free water as well as a Methanol barrier to hinder pathway from penetrating Methanol molecules.
Ji Won Rhim - One of the best experts on this subject based on the ideXlab platform.
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effect of organo clay content on proton conductivity and Methanol Transport through crosslinked pva hybrid membrane for direct Methanol fuel cell
Journal of Industrial and Engineering Chemistry, 2009Co-Authors: Dae Sik Kim, In Cheol Park, Hyun Il Cho, Dae Hoon Kim, Go Young Moon, Hyung Keun Lee, Ji Won RhimAbstract:Abstract In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared using poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA) (PVA:PSSA_MA = 1:7). The PSSA_MA was used both as a crosslinking agent and as a donor of the hydrophilic group (–SO3H and/or –COOH). The hybrid membranes were prepared by modified clay such as Clay Na+, Clay 30B, and Clay 15A. The thermal, water uptake, proton and Methanol Transport properties of the hybrid membrane were found to be sensitive to the clay type and content. The hybrid membrane with Clay 30B shows higher proton conductivity than other hybrid membranes due to hydroxyethyl group. The membrane with Clay 15A showed the lowest Methanol permeability due to lower specific gravity than other clay. Compared to the membrane without modified, the PVA/PSSA_MA/Clay 15A containing 4 wt% of Clay 15A showed both high proton conductivity (0.023 S/cm) and low Methanol permeability (2.19 × 10−7 cm2/s).
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preparation of ion exchange membranes for fuel cell based on crosslinked poly vinyl alcohol with poly styrene sulfonic acid co maleic acid
Journal of Membrane Science, 2006Co-Authors: Dae Sik Kim, Michael D. Guiver, Sang Yong Nam, Tae Il Yun, Mu Young Seo, Se Jin Kim, Ho Sang Hwang, Ji Won RhimAbstract:Crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at various crosslinking temperatures using poly(acrylic acid-co-maleic acid) (PAM) containing different PAM contents. The thermal properties of these PVA/PAM membranes prepared at various reaction temperatures were characterized using differential scanning calorimetry (DSC). The proton conductivity and Methanol permeability of PVA/PAM membranes were then investigated as PAM content was varied from 3 to 13 wt%. It was found that the proton and Methanol Transport were dependent on PAM content in their function both as crosslinking agent and as donor of hydrophilic -COOH groups. Both these properties decreased monotonously with increasing PAM concentration. The proton conductivities of these PVA/PAM membranes were in the range from 10−3 to 10−2S/cm and the Methanol permeabilities from 10−7 to 10−6cm2/sec. In addition, the effect of operating temperature up to 80 °C on ion conductivity was examined for three selected membranes: 7, 9 and 11 wt% PAM membranes. Ion conductivity increased with increasing operating temperature and showed and S/cm at 80 °C, respectively. The effects of crosslinking and ionomer group concentration were also examined in terms of water content, ion exchange capacity (IEC), and fixed ion concentration. In addition, the number of water molecules per ionomer site was calculated using both water contents and IEC values. With overall consideration for all the properties measured in this study, 7∼9 wt% PAM membrane prepared at 140 °C exhibited the best performance. These characteristics of PVA/PAM membranes are desirable in applications related to the direct Methanol fuel cell (DMFC).
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annealing effect of sulfonated polysulfone ionomer membranes on proton conductivity and Methanol Transport
Journal of Membrane Science, 2005Co-Authors: Ho Bum Park, Young Moo Lee, Hyun Soo Shin, Ji Won RhimAbstract:Abstract Sulfonated polysulfone (SPSU) ionomer membranes were prepared via a solution sulfonation method using mixtures of chlorosulfonic acid (HSO 3 Cl) and chlorotrimethylsilane ((CH 3 ) 3 SiCl) as sulfonating agent. Ion exchange capacities (IECs) of SPSU ionomer membranes were controlled by varying the amount of HSO 3 Cl. In the present study, we investigated the thermal transition behavior of SPSU membranes annealed at different temperatures (60 and 150 °C) below glass transition temperature ( T g ) of SPSU ionomer membranes, and also studied the annealing effect on the proton conductivity and Methanol Transport through these ionomer membranes. The changes in T g (°C), ion exchange capacity (IEC, mmol/g), water uptake content (%), proton conductivity (S/cm), and Methanol permeability (cm 2 /s) were reported and discussed. The heat-treatment of SPSU membranes at higher temperature led to the increase in T g and simultaneously the decrease in water uptake, proton conductivity and Methanol permeability. Here, it was found that the annealing below T g accelerated the equilibrium process and physical aging of SPSU ionomer membranes and subsequently induced more compact chain packing structure, which eventually affected the proton and Methanol Transport through these ionomer membranes.
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proton conductivity and Methanol Transport behavior of cross linked pva paa silica hybrid membranes
Solid State Ionics, 2005Co-Authors: Dae Sik Kim, Ho Bum Park, Ji Won Rhim, Young Moo LeeAbstract:Abstract Cross-linked poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA)/silica hybrid membranes were prepared to evaluate the possibility of use as a proton exchange membrane for direct Methanol fuel cell (DMFC). A chemical cross-linking agent having sulfonic acid group (–SO3H) was used to increase proton conductivity, and simultaneously to prevent Methanol Transport through the cross-linked membranes. In addition, silica particles were dispersed into polymer matrices via sol–gel reaction under acidic conditions, expecting the barrier to the Methanol Transport. The proton and the Methanol Transport were investigated in terms of PVA/PAA compositions and cross-linker (sulfosuccinic acid, SSA) concentration. It was found that the compositions of PVA/PAA and the cross-linker concentration affected the Transport properties of the membranes. Particularly, the concentration of cross-linker markedly affected the proton and the Methanol Transport because SSA was used not only as a chemical cross-linker but also as a donor of fixed anionic group (–SO3−H+). The proton conductivities of the hybrid membrane were in the range of 10−3–10−2 S/cm, and the Methanol permeabilities ranged between 10−8 and 10−7 cm2/s. Noticeably, the Methanol permeabilities were reduced by cross-linking between PVA, PAA and SSA chains without a large sacrifice of proton conductivity. Moreover, the silica particles embedded in the cross-linked polymer membranes acted as a reducing material for fraction of free water as well as a Methanol barrier to hinder pathway from penetrating Methanol molecules.
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crosslinked poly vinyl alcohol membranes containing sulfonic acid group proton and Methanol Transport through membranes
Journal of Membrane Science, 2004Co-Authors: Ji Won Rhim, Dae Sik Kim, Ho Bum Park, Choongsub Lee, Jihyun Jun, Young Moo LeeAbstract:Abstract In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared using sulfosuccinic acid (SSA) at different crosslinking temperatures. The crosslinked PVA membranes were also synthesized by varying the amount of SSA (5–30 wt.%) in order to achieve desirable proton conductive properties for fuel cell applications. The crosslinked PVA membranes were characterized using an FT-IR spectroscopy, a thermogravimetric analysis (TGA), and a differential scanning calorimetry (DSC). Ion exchange capacities (IECs) of the crosslinked PVA membranes were in the range of 0.5–2.24 mmol/g. The water content was in the range of 10–80%, depending on the amount of SSA containing sulfonic acid group. The proton conductivities and the Methanol permeabilities through the membranes were investigated in terms of various crosslinking conditions. Especially, it was found that the SSA used in this study played a decisive role in proton conduction (SO3−H+) and at the same time acted as a barrier for Methanol Transport. The proton conductivities and the Methanol permeabilities of all the membranes were in the range of 10−3 to 10−2 S/cm and 10−7 to 10−6 cm2/s in the temperature range of 25–50 °C, respectively, depending on the crosslinking conditions.