• Macromolecular Research
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• v.16 no.5
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• pp.424-428
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• 2008

We prepared an ionic gel polymer electrolyte for dye-sensitized solar cells (DSSCs) without leakage problem. Triiodide compound (BTDI) was synthesized by the reaction of benzene tricarbonyl trichloride with diethylene glycol monotosylate and subsequent substitution of tosylate by iodide using NaI. Bisimidazole was prepared by the reaction of imidazole with the triethylene glycol ditosylate under strongly basic condition provided by NaH. BTDI and bisimidazole dissolved in an ionic liquid were injected into the cells and permeated into the $TiO_2$ nanopores. In situ crosslinking was then carried out by heating to form a network structure of poly(imidazolium iodide), thereby converting the ionic liquid electrolytes to a gel or a quasi-solid state. A monomer (BTDI and bisimidazole) concentration in the electrolytes of as low as 30 wt% was sufficient to form a stable gel type electrolyte. The DSSCs based on the gel polymer electrolytes showed a power conversion efficiency of as high as 1.15% with a short circuit current density of $5.69\;mAcm^{-2}$, an open circuit voltage of 0.525 V, and a fill factor of 0.43.

• Korean Membrane Journal
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• v.11 no.1
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• pp.1-7
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• 2009

This work reports the preparation of proton conductive crosslinked polymer electrolyte membranes by blending poly(vinyl chloride)-g-poly(hydroxyl ethyl acrylate) (PVC-g-PHEA) and poly(vinyl alcohol) (PVA). The PHEA chains of the graft copolymer were crosslinked with PVA using sulfosuccinic acid (SA) via the esterification reaction between -OH of polymer matrix and -COOH of SA. The PVC-g-PHEA graft copolymer was synthesized via atom transfer radical polymerization (ATRP) using direct initiation of the secondary chlorines of PVC backbones. Ion exchange capacity (IEC) continuously increased with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. However, the water uptake increased up to 20.0 wt% of SA concentration above which it decreased monotonically. The membrane exhibited a maximum proton conductivity of 0.026 S/cm at 20.0 wt% of SA concentration, which is presumably due to competitive effect between the increase of ionic sites and the crosslinking reaction.

• KSBB Journal
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• v.25 no.3
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• pp.251-256
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• 2010

A novel method to prepare polyester from wastepaper through liquefaction and crosslinking stages was studied. At the first stage, the liquefaction of wastepaper was carried out in the presence of ethylene glycol under acidic conditions. The factors that affect on liquefaction yield were found to be reaction time, temperature, and acid concentration, and their ranges were 60~120 minutes, $150{\sim}170^{\circ}C$, and 2~4%, respectively. The optimum condition was found to be 100 minutes, $160^{\circ}C$, and 3% sulfuric acid concentration, and the liquefaction yield at this condition was 67%. At the second stage, polyester was prepared from the liquefied wastepaper obtained at the optimum liquefaction condition by crosslinking with succinic anhydride. The effect of reaction time and carboxylic group/hydroxyl group ratio on crosslinkage were investigated at conditions covering 30~50 minutes of reaction time and 1.5~2.5 of carboxylic group/hydroxyl group ratio. The crosslinkages of polyester prepared were 80~90%, which were almost same regardless of reaction conditions.

• Macromolecular Research
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• v.17 no.2
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• pp.84-90
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• 2009

We prepared side-chain liquid crystalline polymers comprising two monomeric units, one having a mesogenic side group that could form a smectic mesophase and the other having a phenolic group attached to the polymer backbone via a thermally reversible urethane bond. The urethane linkage between the isocyanate and phenol groups was stable at room temperature, but it cleaved to generate an isocyanate group when the temperature was increased. When annealed, the copolymers in their smectic mesophases became insoluble in common organic solvents, suggesting the formation of network structures. XRD analysis showed that the annealed polymers maintained their smectic LC structures. The crosslinking process probably proceeded via the reaction of the dissociated isocyanate groups. Some of the isocyanate groups would have first reacted with moisture in the atmosphere to yield amino groups, which underwent further reaction with other isocyanate groups, resulting in the formation of urea bonds. We presume that only polymer chains in the same layer were crosslinked by the reaction of the isocyanate groups, resulting in the formation of a layered polymer network structure. Reactions between the layers did not occur because of the wide layer spacing.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.266-266
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• 2006

The cell spheroid (multicellular mass) is enhanced cell functions because of the cell-cell interaction compared with the individual cell. The objective of this study is synthesis, characterization and evaluation of novel crosslinkers to form spheroid in a short time. Our approach to bridge cells is based on the crosslinking of the cell membrane via the hydrophobic interaction. The crosslinker was prepared by the reaction between ethylenediamine and poly(ethylene glycol) (PEG) derivative with oleyl group as hydrophobic group at the terminal group. The product was characterized with gel permeation chromatography (GPC) and FT-IR. Furthermore, cell culture experiment was also performed to confirm spheroid formation. The function of prepared spheroids was evaluated.

• Elastomers and Composites
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• v.23 no.3
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• pp.223-229
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• 1988

The effect of triazine thiol derivative on the physical properties of silica-polychloroprene(CR) composites and glass fiber(MGF)-CR composites was investigated. Optimum cure time of the MGF composites filled with 2-dibuthylamino-4, 6-dithiol-s-triazine(DBT) was the fastest one, while maximum torque was the best in case of the silica composites filled with s-triazine-2,4,6-trithiol(TAT) on the Oscillating Disk Rheometer(ODR) test. Stress-strain curves of the composites showed that the physical properties such as 100% modulus, 300% modulus, tensile strength of the silica composites filled with DBT was very satisfactory and the silica composites filled with TAT was higher density of crosslinking than other crosslinked elastomer. In aging properties, elastomer filled DBT and TAT were progress post-curing reaction with increasing of aging time and it have been improved the tensile strength and crosslinking density.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.347-349
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• 1999

We have fabricated insulating thin films using p-hexadecoxyphenol(p-Hp) that was formed phenol-formaldehyde resin of crosslinked structure from reaction with formaldehyde by LB technique. For fabricated MIM device, the possibility for insulating layers of electronic were investigated by electrical properties of their LB films according to crosslinking of LB films current-voltage (I-V) properties and frequency-capacitance (C-F) characteristics. We have provided evidence for the high insulating performance of phenol-formaldehyde thin films by the LB method. Conductivity of their LB films was as follows: pure water > 1 % aq. Formaldehyde > heat treatment, in the current-voltage (I-V) characteristics. It is demonstrated that insulation properties of crosslinked p-HP LB films were improved. In capacitance-frequency properties, the heat-treated p-HP LB films for crosslinking showed a low relative dielectric constant.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.233-240
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• 2002

In this work, the cure kinetics and rheological and mechanical properties of diglycidylether of bispheonol A (DGEBA, EP)/polyurethane (PU) blends were investigated. The 1 wt% N-benzylpyrazinium hexafluoroantiminate (BPH) was used as a latent thermal catalyst. Latent properties were performed by measurement of the conversion as a function of reaction temperature using DSC. And the rheological properties of the blend systems were investigated under isothermal conditions using a rheometer. Crosslinking activating energies (Ec) were also determined from the Arrhenius equation based on gel time and curing temperature. The impact strengths were measured as mechanical properties of the casting specimens. The BPH in the blend systems could be an excellent latent thermal catalyst without any co-initiator. The rheological results showed that Ec was highest when PU content was 30 wt% which was in good agreement with the impact strengths. This was probably due to the intermolecular hydrogen bonding between the hydroxyl group in PU and EP, resulting in increasing the crosslinking density.

• Polymer(Korea)
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• v.34 no.5
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• pp.391-397
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• 2010

Poly(amic acid)(PAA) was prepared by reaction of bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylicdianhydride(BTDA) containing double bond for crosslinking and bis[4-(3-aminophenoxy) phenyl] sulfone(BAPS) in N,N-dimethylacetamide(DMAc). The cast film of PAA was heat-treated at different temperatures to create polyimide(PI) films. With increasing thermal crosslinking temperatures from 250 to $350^{\circ}C$, the thermo-mechanical properties, degree of crosslinking, and optical transparency of the cross-linked PI were investigated. The maximum enhancement in the thermo-mechanical properties was observed at a heat treatment condition of $350^{\circ}C$. However, the optical transparency was found to be optimal for $250^{\circ}C$ heat treatment. The degree of crosslinking in NMR was determined to be 85% to 93% with increasing annealing temperature conditions from 250 to $350^{\circ}C$.

• Polymer(Korea)
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• v.38 no.6
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• pp.774-781
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• 2014

Acetylenic or phenylethynyl end-capped polyisoimide oligomers ($M_w$ 2500 g/mol, 5000 g/mol) based upon 4,4'-diamino diphenyl ether (4,4'-ODA)/4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-ODA/3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) were synthesized by using 4-ethynylaniline (4-EA) or 4-phenylethynyl phthalic anhydride (4-PEPA) as an end capper. The incorporation of ethynyl groups were confirmed by FTIR spectroscopy. The isomerization temperature was influenced by molecular weight as well as the backbone structure of polyisoimides oligomers. Thus, polyisoimide oligomers with molecular weight of 2500 g/mol was found to be imidized at temperature $10^{\circ}C$ lower than that for the oligomers with molecular weight of 5000 g/mol. The crosslinking reaction of ethynyl groups occurred at a higher temperature than that for the isoimide/imide isomerization reaction. These two reactions were totally or partially overlapped on the DSC thermograms for the polyisoimide oligomer end-capped with 4-EA. Kinetics of thermal imidization and crosslinking reactions for the 4,4'-ODA/ODPA polyisoimide oligomers end-capped with 4-PEPA were investigated by performing dynamic DSC experiments at heating rate of $10^{\circ}C/min$. The activation energy and pre-exponential factors were 141 kJ/mol and $1.45{\times}10^{13}min^{-1}$ for the imidization reaction and 177 kJ/mol and $2.90{\times}10^{13}min^{-1}$ for the crosslinking reaction, respectively.