Ho Hyoun Jang

Nano Composite Membranes of Sulfonated Amine-Poly(ether sulfone)s and SiO2 for Fuel Cell Application

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.

Synthesis and properties of polycarbonate-co-poly(siloxane-urethane-siloxane) block copolymers

AbstractPolycarbonate-co-poly(siloxane-urethane-siloxane) block copolymers (SiUrPC) were synthesized from siloxane-urethane monomer and polycarbonate (PC) oligomer, and their properties were compared with those of linear Bisphenol A PC (BPA-PC) and siloxane PC (SiPC). The synthesized polymers were characterized by 1H NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). The contact angle of the sessile water drop onto the polymer films was also measured. The thermal and mechanical properties of SiUrPC differed from those of BPA-PC and SiPC. SiUrPC exhibited superior flow properties and lower wettability than BPA-PC.

Preparation and Characterization of Sulfonated Imide-Grafted Poly(ethersulfone)s

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®.

Nano Composite Membranes of Sulfonated Poly(ether sulfone) Containing 4,4-Bis(4-hydroxylphenyl)valeric Acid and SiO2 for PEMFC

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.