• Journal of the Society of Cosmetic Scientists of Korea
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• v.25 no.1
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• pp.55-68
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• 1999

A muti-lamellar emulsion containing a pseudoceramide, N-Ethanol-2-myristyl/ palmityl-3-oxostearmide/arachidamide(PC-9) has been prepared and its efficacy evaluation has been investigated. In order to prepare a muti-lamellar emulsion, first, the gram ratios of PC-9, fatty acid and cholesterol on the phase diagram to be capable of forming their lamellar liquid crystal structures were determined and secondly, the multi-lamellar emulsion was preprared using glyceryl monostearate and polyoxyethylene glyceryl monosteartate as emulsifers together with above mentioned pseudo-stratum corneum lipid components. Besides natural oils such as olive oil had a tendency to build up the multi-lamellar emulsion. And according as the amount of oil increased in the emulsion, it was observed that the optical anisotropy of “Maltese Cross” which was a typical configuration of multi-lamella mesophase texture diminished. In the dried state of the multi-lamella emulsion, it was examined to transform its emulsion phase into a lamella liquid crystal one. And finally, when the emulsion was applied into a human skin, it was investigated that it had effectiveness in reducing transepidermal water loss (TEWL) of the skin.

• Polymer(Korea)
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• v.33 no.3
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• pp.254-262
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• 2009

Nine kinds of hydroxypropyl celluloses (HPCs) with degree of substitution (DS) and molar substitution (MS) ranging from 2.10 to 2.71 and 2.3 to 6.7, respectively and seven kinds of fully butanoated HPCs (BPCs) based on the HPCs with $2.3\;{\le}\;MS\;{\le}\;6.7$ were synthesized, and the molecular characteristics of HPCs and the thermotropic liquid crystalline properties of the derivatives were investigated. MS was nearly equal to DS for small value of DS, but it became exceedly larger than DS for $DS{\gtrsim}1$, showing that in the later stages of reaction, propylene oxide preferentially adds to the side chains rather than the main chain. All the derivatives formed enantiotropic cholesteric phases with right-handed helical structures. The glass and clearing transition temperatures of both HPCs and BPCs were decreased with increasing MS. The optical pitches (${\lambda}_m'S$) of BPCs, as well as HPCs themselves, increased with increasing temperature. However, the ${\lambda}_m'S$ of both HPCs and BPCs at the same temperature increased with increasing MS. Moreover, the temperature dependence of ${\lambda}_m$ of HPCs was weaker than that of BPCs, suggesting that the helical twisting power of the cellulose chain highly depends on the length and chemical structure of the side chain introduced in cellulose chain.

• Polymer(Korea)
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• v.32 no.3
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• pp.230-238
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• 2008

The thermal and optical properties of cellobiose octa(cholestryloxycarbonyl)alkanoates CCCBn, $n=2{\sim}8$,10, the number of methylene units in the spacer) were investigated. All the samples formed monotropic cholesteric phases with left-handed helical structures. CCBn with n=2 or 10, in contrast with CCBn with $3{\leq}n{\leq}8$, did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer connecting the cholesteryl group to the cellobiose chain. The isotropic-cholestropic transition ($T_{ic}$) and glass transition temperatures decreased with increasing n and showed no odd-even effect. The transition entropy at $T_{ic}$ increased with increasing n from 2 up 6, but at n=7 it drops significantly and then increased again with increasing n from 8 to 10. The sharp change at n=7 may be attributed to a difference in arrangement of the side groups. The thermal stability and degree of order in the mesophase and the temperature dependence of the optical pitch observed for CCBn were significantly different from those reported for the cellulose tri(cholesteryloxycarbonyl)alkanoates and glucose penta(cholesteryloxycarbonyl)alkanoates. The results were discussed in terms of the differences in the degree of polymerization, the number of the mesogenic units per mole-glucose unit, and the conformation of the molecules.

• Elastomers and Composites
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• v.39 no.3
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• pp.217-227
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• 2004

A new thermotropic liquid crystalline polymer(TLCP) containing a triad aromatic ester type mesogenic unit and butylene terephthalate unit(BT) in the main chain was synthesized by polycondensation reaction. The TLCP synthesized showed nematic mesophasic behavior and its transition temperature from solid to mesophase was $260^{\circ}C$. The TLCP/PBT blends were prepared by in-situ polymerization in PBT solution and characterized by differential scanning calorimeter(DSC), thermogavimetric analyzer(TGA), scanning electron microscope(SEM), x-ray diffractometer(XRD), and dynamic mechanical thermal analyze, (DMTA). The blends showed well dispersed TLCP phases with domain sizes $0.05{\sim}0.2{\mu}m$ in the PBT matrix. As the increasing TLCP content from 5 to 20 wt%, ${\Delta}Hm$ values of pure PBT in the blend were increased because TLCP acts as a nucleating agent in the PBT matrix. The mechanical properties of the blends depended on the TLCP contents because the TLCP acted effectively as a reinforcing material in the PBT matrix. The blends showed good interfacial adhesion between the TLCP phase and PBT matrix.The blends prepared by in-situ polymerization showed higher mechanical properties and well dispersed TLCP domains than those of the blends prepared by melt blending.

• Polymer(Korea)
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• v.33 no.2
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• pp.144-152
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• 2009

The thermal and optical properties of poly {1-(cholesteryloxycarbonylalkanoyloxy) ethylene}s (PCALEn, n=2$\sim$8,10, the number of methylene units in the spacer) were investigated. All of the homologues formed monotropic cholesteric phases with left-handed helical structures. PCALEn with n=2 or 10, in constrast with PCALEn with $3{\leq}n{\leq}8$, did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer connecting the cholesteryl group to the polyethylene chain. The glass transition temperatures decreased with increasing n. The isotropic-cholesteric phase transition temperatures decreased with increasing n up to 7 and showed an odd-even effect. However it became almost constant when n is more than 7. This behavior is rationalized in terms of the change in the average shape of the side chain on varing the parity of the spacer. This rationalization also accounts for the observed variation of the entropy gain for the clearing transition. The thermal stability and degree of order in the mesophase and the temperature dependence of the optical pitch observed for PCALEn were significantly different from those reported for cellulose tri(cholesteryloxycarbonyl)alkanoates. The results were discussed in terms of the differences in the chemical structure and flexibility of main chain and the number of the mesogenic units per repeating unit.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.640-646
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• 2021

In this study, pitch was synthesized using pyrolysis fuel oil (PFO). Coke with mesophase microstructure was then prepared from the synthesized pitch and its properties were evaluated. Pitch was synthesized by poly-condensation reaction, which is an endothermic reaction at a temperature above 400 ℃ because the PFO was mainly composed of molecules with two to three aromatic rings. The Coke reactor was composed of the pretreatment reactor, preheater for applying heat energy, and coke drum for inducing microstructure of coke. Coke was prepared from synthesized pitch by controlling the temperature of the preheater to 400~490 ℃, and properties were evaluated by polarization microscope, XRD and Raman spectroscopy. The coke prepared at a preheater temperature of 460 ℃ identified flow anisotropic microstructure, and the electrical conductivity was 72.0 S/cm due to high crystallinity. And the flow anisotropic coke showed approximately 2.2 times higher electrical conductivity than that of Super-P, a conductive carbon material.

• Elastomers and Composites
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• v.37 no.4
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• pp.244-257
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• 2002

A thermotropic liquid crystalline polymer(TLCP) which has flexible butylene/hexylene spacers in the main chain and a triad aromatic ester type mesogenic unit containing a naphthyl group was prepared by solution polycondensation. The in-situ composites based on poly(ethylene 2,6-naphthalate) (PEN) and a thermotropic liquid crystalline polymer(TLCP) were prepared and melt spun at different TLCP contents and different draw ratios to produce monofilaments. Blends of the TLCP with PEN were investigated in terms of thermal, mechanical properties and morphology. The TLCP synthesized showed nematic mesophasic behavior and its transition temperature to isotropic melt from mesophase was 249℃. The blends showed well dispersed TLCP phases in the PEN matrix without macroscopic phase separation. Inclusion of TLCP in the blends decreased the cold crystallization temperature of PEN in the blend, therefore, the TLCP acts as a nucleating agent in the blend and showed good interfacial adhesion between the dispersed LCP phases and PEN matrix with domain sizes 40~50 nm in diameter and well developed fibrillation in the monofilaments. The TLCP acted effectively as a reinforcing material in the PEN matrix at the 10wt% level, it led to an increase of initial modulus up to 270% and tensile strength by 235%, while the elongation rate increasing with higher draw ratios.