Papers by Author: Dong Wan Seo

Abstract: Sulfonated poly (ethersulfone) s (S-PDHTPEs) were prepared from 4,4-(2,2-diphenylethenylidene) bisphenol (DHTPE), 4,4-sulfonyldiphenol, 4-fluorophenylsulfone using potassium carbonate, and followed sulfonation reaction with conc. sulfuric acid. DHTPE is a conjugated structure, which enables to form planar conformation between aromatic rings, and selectively sufonated on phenyl rings of polymer side chain. Composite membranes were prepared with copolymers and SiO₂ nanoparticles (20 nm, 4~10%wt). The composite membranes were cast from DMSO. A series of composite membranes structures and characteristic were evaluated by the ¹H-NMR spectroscopy, and thermal stabilities. The membranes were performed by ion exchange capacity (IEC), water uptake and proton conductivity as a function of degree of sulfonation.

Abstract: Sulfonated poly (diphenyl ether ketone sulfone) s, SPDPEKSs were successfully synthesized for proton exchange membranes (PEMs). Poly (diphenyl ether ketone sulfone) s, PDPEKSs were prepared by the polycondensation of 4,4'-sulfonyldiphenol with 1,2-bis (4-fluorobenzoyl)-3,6-diphenylbenzene (BFBDPB) and 4-fluorophenylsulfone respectively, at 210 °C using anhydrous potassium carbonate as catalyst in sulfolane. PDPEKSs were followed by sulfonation using chlorosulfonic acid and concentrated sulfuric acid at two step reactions. Different contents of sulfonated unit of SPDPEKS (25, 35, 45 mol% of BFBDPB) were studied by FT-IR, ¹H NMR spectroscopy, and thermogravimetric analysis (TGA). The ion exchange capacity (IEC), water uptake and proton conductivity of SPDPEKS were evaluated with increase of degree of sulfonation.

Abstract: Poly(ethersulfone)s carrying pendant sulfonated imide side group. The first step in the preparation involved nitration of poly(ethersulfone) (ultrason^®-S6010), with ammonium nitrate and trifluoroacetic anhydride resulting in the nitrated poly(ethersulfone) (NO₂-PES). In the second step, the nitro groups on polymer were reacted with tin(II)chloride and sodium iodide as reducing agents for creating the amino poly(ethersulfone) (NH₂-PES). The imide-poly(ethersulfone)s (IPES) were obtained by reaction of phthalic anhydride and the amino-poly(ethersulfone) with triethyl amine. The sulfonated imide-poly(ethersulfone)s (SIPES) were prepared by chlorosulfonic acid. The different degrees of sulfonated imide units of poly(ethersulfone) were successfully synthesized by an optimized condition. The Sulfonated imide-poly(ethersulfone)s (SIPES) were studied by FT-IR, ¹H-NMR spectroscopy and thermo gravimetric analysis(TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water. The ion exchange capacity (IEC) and proton conductivity of SIPES membranes were evaluated with increase of degree of sulfonation. The water uptake of synthesized SIPES membranes exhibit 30 ~ 65 % compared with 28 % of Nafion 211^®. The SIPES membranes exhibit proton conductivities (25 °C) of 1.21 ~ 2.62´10^-3 S/cm compared with 3.37´10^-3 S/cm of Nafion 211^®.

Abstract: Poly(ether sulfone)s (PES) containing 25-75 mol % valeric acid were prepared with bisphenol A, bis(4-chlorophenyl)sulfone and 4,4-Bis(4-hydroxylphenyl)valeric acid using potassium carbonate in DMAc (dimethylacetamide) at 160 °C. Copolymers containing carboxylacid group were reduced to hydroxy group by BH₃ solution 1M in THF and NaBH4 co-catalyst. Sulfonated poly(ether sulfone)s (S-PES) were obtained by reaction of 1,3-propanesultone and the reduced copolymer (PES-OH) with potassium t-butoxide. Composite membranes were prepared with copolymers and SiO₂ nanoparticles(20 nm, 4-10 wt%). The composite membranes were cast from DMSO.A series of composite membranes were studied by ¹H-NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol.

Abstract: Poly(ether ketone)s (PEK) containing 25-75 mol % valeric acid were prepared with bisphenol A, 4,4-dichlorobenzophenone and 4,4-Bis(4-hydroxylphenyl)valeric acid using potassium carbonate in DMAc (dimethyl acetami de) at 165 °C. Copolymers containing carboxylacid group were reduced to hydroxy group by BH3 solution 1M in THF and NaBH4 co-catalyst. Sulfonated poly(ether ketone)s (S-PEK) were obtained by reaction of 1,3-propanesultone and the reduced copolymer (PEK-OH) with sodium methoxide. A series of copolymers were studied by 1H-NMR spectroscopy, differential scanning calorimeter (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The S-PEK membranes exhibited proton conductivities from 1.31  10-3 to 3.52  10-3 S/cm, water swell from 12.70 to 35.50 %, IEC from 0.45 to 0.75 meq/g and methanol diffusion coefficients from 3.65  10-7 to 5.10  10-7 cm2/S at 25 °C.

Abstract: Organic-inorganic Nano composite membranes were prepared by Sulfonated amine-poly(ether sulfone)s (S-APES)s and SiO2. S-APESs were prepared by nitration, reduction and sulfonation of poly(ether sulfone) (ultrason®-S6010). Poly(ether sulfone) was reacted with ammonium nitrate and trifluoroacetic anhydride to produce the nitrated poly(ether sulfone), and was followed by reduction using tin(Ⅱ)chloride and sodium iodide as reducing agents to give the amino-poly(ether sulfone). The S-APES was obtained by reaction of 1,3-propanesultone and the amino-poly(ether sulfone) (NH2-PES) with sodium methoxide. The different degrees of nitration and reduction of poly(ether sulfone) were successfully synthesized by an optimized process. Organic-inorganic nano composite membranes were obtained by mixing S-APES (45 %) with hydrophilic SiO2 (20 nm, 4-10 %) obtained by sol-gel process. Different contents of SiO2 of the S-APES were studied by FT-IR, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The ion exchange capacity (IEC), a measure of proton conductivity, was evaluated. The nano composite membranes exhibit conductivities (25 °C) from 3.51 x 10-3 to 4.10 x 10-3 S/cm, water swell from 57.25 to 60.50 %, IEC from 0.68 to 0.73 meq/g, and methanol diffusion coefficients from 2.81 x 10-7 to 3.33 x 10-7 cm2/S at 25 °C.

Abstract: Poly(ether sulfone)s (PES) containing 25-75 mol % valeric acid were prepared with bisphenol A, bis(4-chlorophenyl)sulfone and 4,4-Bis(4-hydroxylphenyl)valeric acid using potassium carbonate in DMAc (dimethylacetamide) at 160 °C. Copolymers containing carboxylacid group were reduced to hydroxy group by BH3 solution 1M in THF and NaBH4 co-catalyst. Sulfonated poly(ether sulfone)s (S-PES) were obtained by reaction of 1,3-propanesultone and the reduced copolymer (PES-OH) with potassium t-butoxide. A series of copolymers were studied by 1H-NMR spectroscopy, differential scanning calorimetry (DSC), and thermo gravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. The S-PES membranes exhibited proton conductivities from 1.20  10-3 to 3.40  10-3 S/cm, water swell from 12.25 to 31.50 %, IEC from 0.43 to 0.72 meq/g and methanol diffusion coefficients from 3.60  10-7 to 4.90  10-7 cm2/S at 25 °C.

Abstract: The Sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) / poly(2,6-diphenyl-1,4-phenylene oxide) (S-PPO) was prepared by oxidative coupling polymerization with 2,6-dimethyl phenol, 2,6-diphenyl phenol, CuCl(І) and pyridine, and followed sulfonation with chlorosulfonic acid. Copolymer was consisted of 2,6-diphenyl phenol 30 mol% and 2,6-dimethyl phenol 70 mol%. Organic-inorganic nano composite membranes were prepared with copolymer and a series of SiO2 nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solution. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. S-PPO copolymer and nano composite membranes exhibited proton conductivities from 0.79×10-3 to 0.98×10-3 S/cm, water uptake from 21.70 to 24.77 %, IEC from 0.720 to 0.955 meq/g and methanol diffusion coefficients from 2.97×10-7 to 3.70×10-7 cm2/S.

Abstract: A series of sulfonated poly(aryl ether ketone)s were prepared by condensation polymerization with bisphenol A and 1,2-bis(4-fluorobenzoyl)-3,6-diphenylbenzene, and followed by sufonation with chlorosulfonic acid. The polymers were characterized by Fourier transform infra-red (FTIR) and ion exchange capacity (IEC) to verify sulfonation. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out to investigate the thermal stability of the prepared membranes. The membranes were found to possess all the requisite properties; Ion exchange capacity (3.31meq./g), glass transition temperatures (207-230°C), and low affinity towards methanol (2.04x10-6-4.15x10-7 cm2/S).

Abstract: Branched sulfonated poly(ether sulfone-ketone) copolymer was prepared with bisphenol A, 4,4-difluorobenzophenone, sulfonated chlorophenyl sulfone (40mole% of bisphenol A) and THPE (1,1,1-tris-p-hydroxyphenylethane) as a branching agent. THPE was used 0.4 mol% of bisphenol A to synthesize branched copolymers. Organic-inorganic nano composite membranes were prepared with copolymer and a series of SiO2 nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solutions. The films were converted from the salt to acid forms with dilute hydrochloric acid. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. Branched copolymer and nano composite membranes exhibited proton conductivities from 1.12x10-3 to 6.04x10-3 S/cm2, water uptake from 52.9 to 62.4%, IEC from 0.81 to 1.21 meq/g and methanol diffusion coefficients from 1.2x10-7 to 1.5x10-7 cm2/S.