Young Don Lim

Synthesis and Characterization of Grafted Silicone Polycarbonates

Grafted silicone polycarbonates were synthesized from precursors, which are allyl polycarbonates (Allyl-PCs), and siloxanes by hydrosilylation reaction using Karstedts catalyst. Allyl-PCs were synthesized using polycarbonate oligomer and 3,3′-diallyl bisphenol A (DABA) through an interfacial polymerization process. FT-IR, 1H-NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC) were studied in order to understand the characterization of the synthesized compounds. Atomic force microscopy (AFM) was used to observe the surface morphology of the polymer films. The contact angle measurement of the sessile water drop onto the polymer films was also performed. The silicone polycarbonates (Si-PC) and their active precursors (Allyl-PC) were different in thermal properties to that of the bisphenol A polycarbonate (BPA-PC). Grafted silicone polymers exhibited lower wettability than those of their precursors and BPA-PC.

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 Characterization of Poly(ether ketone) Containing Side Sulfonic Acid Group for Proton Exchange Membrane Fuel Cell

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.

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 Poly(ether Sulfone) Using 4,4-Bis(4-Hydroxylphenyl)valeric Acid for Proton Exchange Membrane Fuel Cell Application

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.

Novel cyclotetrasiloxane tetraimidazolium salts as high performance quasi-solid state electrolyte for dye-sensitized solar cells

AbstractA new type of quasi-state ionics based on cyclosiloxane imidazolium iodides was synthesized and used as electrolytes in dye-sensitized solar cells (DSSCs). The cyclosiloxane electrolyte formed a distinctive cavity in the center of the molecule, and the cyclic Si-O linkages were surrounded with bulky tetraimidazolium salts on the outside. The resulting electrolytes were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis (TGA). The electrolytes exhibited dark brown quasi-solid state, high viscosity, and excellent long term stability. The cell efficiency tended to depend on the chain length of the electrolyte, and was slightly higher in the propylimidazolium electrolyte (ηmax=8.2%) than in the methylimidazolium one. The superior long-term stability of the fabricated, cyclosiloxane electrolyte-based DSSCs demonstrated that they hold great promise in overcoming the current issues affecting on cell performance.

Nano Composite Membranes of Poly(ether sulfone)s Containing Multi-Sulfonated Hexaphenylbenzene and SiO2 for PEMFC

Poly (ether sulfone) membranes (PHP) were prepared with 25 mol% of 1,2-bis (4-hydroxybenzene)-3,4,5,6-tetraphenylbenzene (BHPTPB). BHPTPB has a conjugated propeller-like nonplanar conformation structure containing the peripheral seven aromatic rings which facilitate the formation of π-π interactions. A series of sulfonated poly (ethersulfone) s (SHP 25) was synthesized with concentrated sulfuric acid. The sulfonation took place selectively on the multiphenyl unit, and simultaneously on the side-chain phenyl groups. 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.

Nano Composite Membranes of Sulfonated Poly(ether sulfone)s Containing Tetraphenylethylene moiety and SiO2 for PEMFC

Conjugated cis/trans isomer-based polymer membranes were prepared with 25 mol% of bis (4-hydroxyphenyl)-1,2-diphenylethylene (BHDPE). BHDPE has a conjugated nonplanar conformation structure containing the peripheral four aromatic rings which facilitate the formation of π-π interactions. A series of sulfonated poly (ethersulfone) s (SPBHDPE) was synthesized with concentrated sulfuric acid. The sulfonation took place selectively on the BHDPE unit, and simultaneously on the side-chain and main-chain phenyl groups. The SPBHDPEs consisted of a 4:6 ratio of cis and trans form mixtures. 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.

Nano Composite Membranes of Sulfonated Poly(ether sulfone)s Containing DHTPE and SiO2 for PEMFC

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.

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®.