• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.305-309
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• 2020

In this study, a series of ionic liquids based electrolytes for lithium batteries were prepared by mixing the anion functionalized ionic liquid, [DMIm][MPEGP] (1,3-dimethylimidazolium (2-methoxy(2-ethoxy(2-ethoxy)))-ethylphosphite), with the lithium salt, LiTf₂N (lithium bis(trifluoromethanesulfonyl)imide), and the concentration of lithium salt was varied between 0 and 3.0 molar ratio. We observed the ionic mixtures became opaque and spontaneously aggregated to form a thermotropic ionic liquid crystal. Extensive spectroscopic examinations of the ionic liquid crystals were carried out to investigate their self-organized structures and the ion transport behavior depending on the concentration of lithium salt. An increase in the ionic conductivity was observed for the ionic liquid crystals related to the ability to form ion diffusion pathways along the ordered structures, resulting in improved electrochemical performances of lithium batteries.

• Polymer(Korea)
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• v.30 no.4
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• pp.338-349
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• 2006

Fully or nearly fully(8-cholesteryloxycarbonyl)heptanoated polysaccharide derivatives were synthesized by reacting cellulose, amylose, chitosan, chitin, alginic acid, pullulan or amylopectin with (8-cholesteryloxycarbonyl)heptanoyl chloride (CH8C), and their thermotropic liquid crystalline behaviors were investigated. Like in the case of CH8C, all the polysaccharide derivatives formed monotropic cholesteric phases with left-handed helicoidal structures whose optical pitches $({\lambda_m}'s)$ decrease with increasing temperature. Amylopectin derivative also formed a monotropic cholesteric phase with lefthanded helicoidal structures but, in contrast with the other derivatives, did not display reflection colors over the full cholesteric range, suggesting that the helicoidal twisting power of the cholesteryl group highly depends on the branched structure in amylopectin. The thermal stability and degree of order in the mesophase, the magnitude of ${\lambda}_m$ at the same temperature, and the temperature dependence of the ${\lambda}_m$ observed for polysaccharide derivatives were entirely different from those reported for the polymers in which the cholesteryl groups are attached to flexible or semiflexible backbones through flexible spacers. The results were discussed in terms of the difference in the chemical structures of the main and side chains and flexibility of the main chain.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.504-511
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• 2008

Two kinds of nitroazobenzene derivatives: 4-{4'-(nitrophenylazo)phenoxy}alkanoic acids (NAAn, n = 2~8, 10, number of methylene units in the alkyl chain) and 4-{4'-(nitrophenylazo)phenoxy}alkanoyl chlorides (NACn, n = 2~8, 10) were synthesized, and their thermotropic liquid crystalline behaviors were investigated. NAA6 formed an enantiotropic nematic phase, while the remainders, except NAA2, showed monotropic nematic phases. Isotropic-nematic transition temperature ($T_{iN}$) and change of entropy (${\Delta}S$) at $T_{iN}$ for both of NAAn and NACn varied by the change of n, and pronounced odd-even effects of n were also observed. However, the $T_{iN}$ and ${\Delta}S$ values of NAAn were much higher than those of NACn. This fact may be attributed to the hydrogen bonding between carboxyl groups. Thermal properties and degree of order in the mesophase and the magnitude of the odd-even effects of both NAAn and NACn were significantly different from those reported for 4-(alkoxy)-4'-nitroazobenzenes. It was discussed in terms of the differences in the molecular anisotropy and the temperature-dependent flexibility of the substituted groups.

• Polymer(Korea)
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• v.33 no.1
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• pp.58-66
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• 2009

The thermotropic liquid crystalline behavior of the homologous series of cellulose tri[4-{4'-(nitrophenylazo) phenoxycarbonyl}] alkanoates (NACEn, n=2$\sim$8, 10, the number of methylene units in the spacer) have been investigated. All of the homologoues formed monotropic nematic phases. The isotropic-nematic transition temperature ($T_{iN}$) decreased when n is increased up to 7, but it became almost constant when n is more than 7. The plot of transition entropy at $T_{iN}$ against n had a sharp negative inflection at n=7. The sharp change at n=7 may be attributed to the difference in arrangement of the side groups. The melting temperature ($T_m$) and associated entropy change at $T_m$, in contrast with $T_{iN}$ and associated entropy change at $T_{iN}$, exhibited a distinct odd-even effect, suggesting that the average shape of the side chains in the crystalline phase is different from that in the nematic phase. The thermal stability and degree of order of the nematic phase observed for NACEn were significantly different from those reported for the homologous series of side-chain and combined type liquid crystal polymers bearing azobenzene or biphenyl units in the side chains. The results were discussed in terms of the differences in the chemical structure, the flexibility of the main chain, the mode of chemical linkage of the side group with the main chain, and the number of the mesogenic units per repeating unit.

• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.67-75
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• 2001

A new homologous series with the general formula in which n is the longitudinal alkyloxy group, n=1-10, was synthesized. The thermotropic and liquid crystalline properties were studied by differential scanning calorimetry and on the hot-stage of a polarizing microscope. All of the new compounds were monotropic and texture observations proved that all investigated homologues with n=1-10 exhibited nematic phases. Also, the compounds showed pronounced alternation effects in the homologous series with constant lateral bridging group, oxydecamethyleneoxy, but increasing longitudinal chains, n.

• Journal of the Korean Chemical Society
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• v.41 no.3
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• pp.157-165
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• 1997

The transesterification reaction could be used to the technical production as it forms an in-situ compatibilizer during the processing of polymer blends. Thus, TR-4,6(poly(tetramethylene-4,4'-terephthaloyldioxydibenzoate-co-hexametylene-4,4'-terephthaloyldioxydibenzoate), one of thermotropic liquid crystalline polymers was synthesized and was blended with PBT(polybutylene terephthalate), one of engineering plastics, to study the transesterification reaction. The transesterification reactions between two components, TR-4,6 and PBT, were monitored by IR, DSC and $^{13}C-NMR$ and analyzed by a statistical treatment method. Also, the reaction rates and the sequence distributions of repeating unit were (calculated and) invesitigated.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.76-83
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• 1997

Blends of thermotropic liquid crystalline polymer(TLCP) with poly(ethylene terephthalate) (PET) were prepared by the coprecipitation from a common solvent. The blends were processed through a capillary die at $287^{\circ}C$ to produce a monofilament. Morphology and mechanical, thermal properties of blends and composites were examined by differential scanning calorimetry(DSC), tensile test, optical microscopy and scanning electron microscopy. Crystallization kinetics of the blends were investigated by the isothermal DSC method. The Avrami analyses were applied to obtain the information on the crystal growth geometry and factors controlling the rate of crystallization. In the blends, liquid crystalline phase did not reveal any significant macrophase separation and thermal degradation at the processing temperature. From scanning electron micrographs of cryogenic fracture surfaces of extruded fibers, the TLCP domains were found to be more or less finely dispersed with $0.1{\mu}m$ to $0.2{\mu}m$ in size. Interfacial adhesion between the TLCP and matrix polymer was excellent. Tensile strength and modulus of TLCP/PET in-situ fiber composites were enhanced with increasing draw ratio and LCP content.

• Polymer(Korea)
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• v.30 no.1
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• pp.35-44
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• 2006

Poly[1-(cholesteryloxycarbonyloxy)ethylene](PCOE) and poly[1-(cholesteryloxycarbonylheptanoyloxy)ethylene] (PCOSE) were prepared by reacting poly(vinyl alcohol) with cholesteryl chloroformate or 8-cholesteryloxycarbonylheptanoly] chloride (CH8C), and their thermal and optical properties were investigated. CH8C formed a monotropic cholesteric phase whereas PCOE and PCOSE exihibited enantiotropic cholesteric phases. Like in the case of CH8C, the optical pitch $(\lambda_m)$ of PCOSE decreased with increasing temperature. PCOE, contrast with PCOSE, did not display reflection colors, suggesting that the helical twisting power or the cholesteryl group highly depends on the length or the spacer joining the cholesteryl group to the main chain. The mesophase properties of PCOE and PCOSE were entirely different from those of poly $(cholesteryl-\omega-acryloyloxyalkanoates)$. The results indicate that the mode of chemical linkage of the side chain group with the main chain plays an important role in the formation, stabilization, and temperature dependence of $\lambda_m$ of the cholesteric mesophase.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.47-52
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• 2014

A series of liquid crystalline polyesters containing X-shaped mesogenic groups in main chain were synthesized through the solution polymerization of 2,5-di(4-substituted benzoate)hydroquinones and 4,4'-dicarboxy-1,8-diphenoxyoctane. The structures and properties of synthesized polymers were investigated by $^1H$-NMR, FT-IR, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), polarized optical microscopy (POM) and wide angel X-ray diffraction (WXRD). Inherent viscosities (${\eta}_{inh}$) of polymers were measured between 0.35 and 0.66 dL/g in 1,1,2,2-tetrachloroethane, and they were easily soluble in most of organic solvents used for this experiment. All polymers revealed relatively low melting transition temperature ($T_m$) and crystallinity, and also showed thermotropic nematic liquid crystallinity when they were heated to their melting temperatures. These properties of polymers were presumably due to the presence of the bulky substituting groups on the hydroquinone unit in mesogenic group.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.223-226
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• 2003

Due to the potential application to ultra-high strength fibers and excellent properties such as high mechanical properties, excellent thermal endurance and chemical stability, thermotropic liquid crystal polymers (TLCPS) are attractive in recent years [1, 2]. Furthermore, the melt blends of TLCPS and conventional thermoplastics have been extensively investigated because of their easy processing and high performance [3-6]. Since high performance polymers generally has high melt viscosity, introduction of the relatively low viscosity components may be one of the more effective techniques to improve processability through the decrement of melt viscosity in melt processing. (omitted)