• Bulletin of the Korean Chemical Society
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• v.18 no.12
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• pp.1264-1268
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• 1997

The poly(methylsilene) (1) was modified with the group 4 metallocene Cp2MCl2/Red-Al (M = Ti, Zr, Hf) combination catalyst and with the group 6 metal carbonyl M(CO)6 (M = Cr, Mo, W) catalyst, producing the highly cross-linked isoluble polymer and the lowly cross-linked soluble polymer, respectively. An interrelationship between molecular weight and percent ceramic residue yield with metal within the respective group was not found. The polymers modified with the group 4 metallocene combination catalysts have higher molecular weight and lower percent ceramic residue yield than the polymers modified with the group 6 metal carbonyl catalysts do. The catalytic activity of group 4 metallocene combinations appears to be higher at ∼100 ℃, but to be lower at very high temperature than those of group 6 metal carbonyls. The pyrolysis of the modified 1 yielded SiC ceramic.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.63-68
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• 2008

We investigated the recycling method to re-plasticize cross-linked polyethylene by using supercritical methanol. The cross-linked polyethylene is successfully fragmented to thermoplasticized polyethylene with little degradation reactions in supercritical fluids. The thermo-plasticization reaction was accelerated with increase in temperature in the range from $360^{\circ}C$ to $400^{\circ}C$, resulting in decrease in crosslinking density, molecular weight and mechanical properties. However, the thermoplasticized polyethylene at $360^{\circ}C$ showed comparable tensile strength and impact strength with a raw resin of crosslinked polyethylene. Chemical structure of main chain of polyethylene was not affected by reaction condition.

• Polymer(Korea)
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• v.38 no.1
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• pp.80-84
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• 2014

Polymer nanoparticles with cross-linked core and PBA/PS double-shell were synthesized and their baroplastic properties were characterized. PBA/PS, the inner and outer shell with cross-linked core consisting of St and DVB were synthesized by three-stage emulsion polymerization. The obtained materials exhibited pressure-induced mixing of their components and could be processed at $25^{\circ}C$ by compression molding which means there was no effect of the presence of cross-linked core. Interestingly, the Young's modulus of molded objects has found to be affected strongly by the size of double-shell nanoparticles. Furthermore, the molded object of higher PBA content was successfully recycled 5 times at $25^{\circ}C$ and showed 0.55 MPa of modulus and 1.81 MPa of strength at break.

• Journal of Integrative Natural Science
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• v.4 no.3
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• pp.177-181
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• 2011

The catalytic dehydrocoupling of bis(1-sila-3-butyl)benzene 1 and 2-phenyl-1,3-disilapropane 2 by $Cp_2ZrCl_2$/Red-Al and $Cp_2ZrCl_2$/n-BuLi was reported to compare their catalytic efficiency. The dehydrocoupling of monomeric silanes 1 with the $Cp_2ZrCl_2$/Red-Al and $Cp_2ZrCl_2$/n-BuLi combination catalysts produced two phases of polymers: one is a highly cross-linked insoluble solid, and the other is noncross-linked or slightly cross-linked soluble oil and could be a precursor for the solid polymer. The dehydrocoupling of 2 with the $Cp_2ZrCl_2$/n-BuLi combination catalyst similarly produced two phases of polymers. By contrast, the catalytic reaction of 2 with the $Cp_2ZrCl_2$/Red-Al combination catalyst produced a soluble polymer via redistribution/dehydrocoupling process.

• Journal of Hydrogen and New Energy
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• v.28 no.1
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• pp.17-23
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• 2017

Polyether ether ketone (PEEK) composite including tungstophosphoric acid(TPA) membranes have been intensively investigated for polymer electrolyte membrane water electrolysis (PEMWE) and thus covalently linked sulfonated polyether ether ketone (CL-SPEEK) with captured TPA composite membranes were prepared and characterized. Sulfonated polyether ether ketone (SPEEK) was prepared in sulfonation of PEEK and was cross-linked with 1,4 diiodobutane. The carbonyl group of SPEEK was reduced with $NaBH_4$ and 3-isocyanatepropyltriethoxysilane (ICPTES) was added. The TPA captured composite was prepared in reaction of TPA with 3-mercaptopropyltrime thoxysilane (MPTMS). The polymer composite membranes showed better thermostability and electrochemical properties than SPEEK. The membranes were prepared by sol-gel casting method. The polymer composite membrane featured 0.1285 S/cm of proton conductivity at $80^{\circ}C$ and outstanding durability.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.608-612
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• 2012

We investigated the cycling behavior of $Li_4Ti_5O_{12}$ electrode in a cross-linked gel polymer electrolyte based on non-flammable ionic liquid consisting of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide and vinylene carbonate. The $Li_4Ti_5O_{12}$ electrodes in ionic liquid-based gel polymer electrolytes exhibited reversible cycling behavior with good capacity retention. Cycling data and electrochemical impedance spectroscopy analyses revealed that the optimum content of the cross-linking agent necessary to ensure both acceptable initial discharge capacity and good capacity retention was about 8 wt %.

• Bulletin of the Korean Chemical Society
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• v.18 no.3
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• pp.318-323
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• 1997

ο-(2-Vinyloxyethoxy)benzylidenemalononitrile (3a) and methyl ο-(2-vinyloxyethoxy)-benzylidenecyanoacetate (3b), m-(2-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl m-(2-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of ο-(2-vinyloxyethoxy)benzaldehyde (1) and m-(2-vinyloxyethoxy)benzaldehyde (2) with malononitrile or methyl cyanoacetate, respectively. Bifunctional vinyl ether monomers 3a and 3b polymerized quantitatively with radical initiators in γ-butyrolactone solution at 65 ℃, while meta-isomers 4a and 4b gave lower yields of polymers under the same conditions. The polymers 5-6 obtained from the monomers 3-4 were insoluble in common solvents due to cross-linking. Under the same polymerization conditions ethyl vinyl ether polymerized well with model compounds ο-methoxybenzylidenemalononitrile 7a, methyl ο-methoxybenzylidenecyanoacetate 7b, m-methoxybenzylidenemalononitrile 8a, and methyl m-methoxybenzylidenecyanoacetate 8b, respectively, to give 1:1 alternating copolymers 9-10 in high yields. Cross-linked polymers 5-6 showed a thermal stability up to 300 ℃, and showed a double phase degradation pattern in their TGA thermograms. Polymers 5-6 showed broad endothermic bands around 75-110 ℃ without any characteristic Tg peaks in DSC thermograms. Alternating copolymers 9-10, except copolymer 9b were soluble in common organic solvents. The inherent viscosities of polymer 9-10 were in the range of 0.35-0.62 dL/g. Polymer films cast from acetone solution were cloudy and tough and Tg values obtained from DSC thermograms were in the range of 118-165 ℃.

• Membrane Journal
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• v.30 no.4
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• pp.252-259
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• 2020

Olefins are industrially important materials used for the synthesis of various petrochemicals. During the polymerization process, unreacted olefin monomers are discharged together with a large amount of nitrogen. For economic benefits, these olefin gases should be efficiently separated from nitrogen. In this study, a poly(glycidyl methacrylate-co-methyl methacrylate) (PGM) comb-like copolymer was synthesized and 4,4'-diaminoazobenzene (DAAB) was introduced to the copolymer to prepare a cross-linked membrane for C₃H₆/N₂ separation. PGM and DAAB were readily reacted at room temperature through an epoxide-amine reaction without additional thermal treatment. PGM-based membrane, which is a glassy polymer, showed a faster permeation of N₂ compared to C₃H₆. The pristine PGM membrane exhibited the N₂ permeability of 0.12 barrer and the high N₂/C₃H₆ selectivity of 32.4. As DAAB was introduced as a cross-linker, the thermal stability of the membrane was significantly improved, which was confirmed by TGA result. The N₂/C₃H₆ selectivity was decreased at 1 wt% of DAAB content, but the N₂ permeability increased by approximately 4.7 times. We analyzed N₂/C₃H₆ gas separation properties through a glassy polymer-based membrane, which has not been widely studied. Also, we proposed that thermal stability of the membrane can be greatly improved by the cross-linking method.

• Macromolecular Research
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• v.17 no.7
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• pp.522-527
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• 2009

A photocrosslinkable polyphosphazene was used for molecular imprinting. We synthesized polyphosphazene (3) having urea groups for complexation with N-carbobenzyloxyglycin (Z-Gly-OH, template) and chalcone groups for cross-linking reaction. As substituents, 4-hydroxycha1cone (1) and N-(4-hydroxyphenyl)-N'-ethylurea (2) were prepared. Choloro groups of poly(dichlorophosphazene) were replaced by the sequential treatment with sodium salts of compounds 1 and 2, and trifluoroethanol. The template molecule was complexed with the urea groups on the polymer chains via hydrogen bonding. A thin polymer film was prepared by casting a solution of the complex of polymer 3 and the template in dimethylformamide on a quartz cell and irradiated with 365 nm UV light to yield a cross-linked film with a thickness of about $16{\mu}m$. The template molecules in the film were removed by Soxhlet extraction with methanol/acetic acid. The control polymer film was prepared in the same manner for the preparation of the imprinted polymer film, except that the template and triethylamine were omitted. In the rebinding test, the imprinted film exhibited much higher recognition ability for the template than the control polymer. We also investigated the specific recognition ability of the imprinted polymer for the template and its structural analogues. The rebinding tests were conducted using Z-Glu-OH, Z-Asp($O^tBu$)-OH, and Z-Glu-OMe. The imprinted film showed higher specific recognition ability for the template and the lowest response for Z-Asp($O^tBu$)-OH.

• Korean Membrane Journal
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• v.10 no.1
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• pp.1-7
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• 2008

Polystyrene-co-divinylbenzene (PS-co-DVB) asymmetric membranes were prepared. In order to control their structure and mechanical properties the degree of cross-linking and the composition of casting solution were varied. The rubber added PS-DVB membranes was also prepared to overcome the mechanical limitation of cross-linked membrane, and their mechanical properties were investigated. It was revealed that the concentration of polymer in the casting solution affected the determination of skin formation. When the PS-co-DVB membrane consists of styrene-butadiene (SB) rubber or liquid polybutadiene (PBD), the structures formed showed that the PS content in the PS/DVB system played an important role in determining the porous sublayer structure.