• 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.

• Membrane Journal
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• v.13 no.2
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• pp.110-117
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• 2003

Sulfonated polyimides had been utilized and studied widely as available materials in chloro-alkali electrolysis, cationic exchange resins, and so on. However, a slow decrease in performance during experiments had been reported, which could be attributed to a loss of ionic conductivity related to either a continuous dehydration or polymer degradation. One of main reasons to account for the degradation of sulfonated polymers is the hydrolysis leading to polymer chain scission and decrement of molecular weight. Therefore, the objective of our study was to investigate possible imide cycle and additional ester bond cleavage connected with $SO_3$H presence under hydrated condition. In order to confirm and obtain as clear information as possible about breakages of bonds via $^1H\; and \;^{13}C$ NMR and IR spectroscopic analyses, our study was performed by model compound. Consequently, model compounds with both phthalic and naphthalenic imide ring and ester bonds were synthesized to evaluate the hydrolysis stability of sulfonated polyimide. The experiments were performed for prepared model compounds before and after aging in deionized water at $80^{\circ}C$ and were terminated by lyophilization technique. The aging products were finally analyzed by NMR and IR spectroscopy.

• Polymer(Korea)
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• v.33 no.6
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• pp.555-560
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• 2009

Sulfonic acid of the sulfonated 6FDA-based polyimides were exchanged with the monovalent ($Li^+$, $Na^+$, $K^+$) and divalent ($Mg^{2+}$, $Ca^{2+}$, $Ba^{2+}$) ions. The effect of metal cations exchanged sulfonated polyimides was investigated in terms of gas permeability and selectivity for $CO_2$, $O_2$ and $N_2$ gases. Thermogravimetric analysis showed that thermal stability of sulfonated polyimide was improved by exchanged metal cations. The permeabilities of monovalent cation-exchanged, sulfonated polyimide were reduced as the ion radius reduced [$Li^+$(0.059 nm)>$Na^+$(0.102 nm)>$K^+$(0.138 nm)], and those of divalent cations exchanged were determined by the ionic radii and electrostatic crosslinking between the polymer and metal cations, whereas the selectivities of all the metal cation-exchanged, sulfonated polyimides for $CO_2/N_2$ and $O_2/N_2$, were higher than those of sulfonated polyimide membranes. The sulfonated polyimide exchanged with the potassium cation showed the $O_2$ permeability of 89.98 Barrer [$1\times10^{-10}\;cm^3$(STP) $cm/cm^2{\cdot}s{\cdot}cmHg$] and the sulfonated polyimide exchanged with the lithium cation showed the $O_2/N_2$ selectivity of 12.9.

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.245-250
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• 2009

Crosslinked membrane based on sulfonated polyimide was prepared by the introduction of crosslinkable monomer in polymerization process and crosslinking during membrane casting. Crosslinked membranes showed different properties from non-crosslinked membranes. Crosslinking decreased methanol crossover and therefore unit cell using crosslinked membrane showed increased open circuit voltage, 0.81 V, in comparison with unit cell using noncrosslinked membrane, 0.71 V. In addition, water uptake of crosslinked membrane, 40.5%, was lower than that of non-crosslinked membrane, 57.0%, and this resulted in improved dimensional stability. However, proton conductivity of crosslinked membranes showed rather low relative to non-crosslinked membrane due to reduced water uptake.

• 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.

• Polymer(Korea)
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• v.36 no.4
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• pp.486-493
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• 2012

Photocurable sulfonated polyimide (SPI) polyelectrolyte containing chalcone group was prepared and fabricated on an alumina electrode pretreated with chalcone-containing silane-coupling agent. SPI films with bis(tetramethyl)ammonium 2,2'-benzidinedisulfonate ($Me_4N$-BDS)/4,4'-diaminochalcone (DAC)/pyromellitic dianhydride (PA)= 90/10/100 possessed very linear response(Y = -0.04528X+7.69446, $R^2=0.99675$) and showed resistance changing from 4.48 to $2.1k{\Omega}$ between 20 and 95 %RH. The response time for absorption and desorption measurements between 33 and 94 %RH% was about 79 s, which affirmed the high efficiency of crosslinked SPI film for rapid detection of humidity. A negative temperature coefficient showing $-0.49%RH/^{\circ}C$ was found and proper temperature compensation should be considered in future applications. Moreover, pretreatment of the substrates with chalcone-containing silane-coupling agent was performed to improve the water durability and the stability of the humidity sensors at a high humidity and a high temperature and long-term stability for 480 h. The crosslinked SPI films anchored to electrode substrate could be a promising material for the fabrication of efficient humidity sensors with superior characteristics compared to the commercially available sensors.

• 한국전기화학회:학술대회논문집
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• 2002.07a
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• pp.219-222
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• 2002

• Proceedings of the Membrane Society of Korea Conference
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• 2001.11a
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• pp.75-78
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• 2001

• Membrane Journal
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• v.19 no.3
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• pp.237-243
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• 2009

Polyimides synthesized by using 2,2'-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and 4,4'-diaminodiphenylmethane (DAM) were sulfonated according to reaction times, 5 min to 20 min. And the resulting polyimide membranes were investigated in terms of permeability and separation factor for $N_2$, $O_2$, and $CO_2$ gases. The introduction of bulky group, $-{SO_3}H$, leads to the decreases of both diffusivities and solubilities for all the range of reaction times. At 20 min of sulfonation, the diffusivity and solubility of $N_2$ decrease up to 21% and 26%, respectively. Overall separation efficiencies for $O_2/N_2$ and $CO_2/N_2$ increase as the reaction time increases to 20 min.

• Macromolecular Research
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• v.17 no.10
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• pp.725-728
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• 2009