• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.475-482
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• 2007

The thermal and optical properties of glucose penta(cholesteryloxycarbonyl)alkanoates (CAGLn, n = 2~8, 10, the number of methylene units in the spacer) were investigated. All the CAGLn formed monotropic cholesteric phases with left-handed helical structures. CAGLn with n = 2 or 10, in contrast with CAGLn 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 joining the cholesteryl group to the glucose chain. The isotropic-cholesteric transition point ($T_{ic}$) decreased with increasing n and showed no odd-even effect. The plot of transition entropy at $T_{ic}$ against n had a sharp negative inflection at n = 7. The optical pitches (${{\lambda}_m}^{\prime}$ s) of CAGLn with $3{\leq}n{\leq}8$ decreased with increasing temperature. However, the temperature dependence of the ${\lambda}_m$ of the derivatives exhibited pronounced dependence on n. The transitional properties and the temperature dependence of the ${\lambda}_m$ observed for CAGLn were discussed in terms of the differences in arrangement of the cholesteryl groups and the conformation of the molecules.

• 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.

• Polymer(Korea)
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• v.32 no.5
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• pp.446-457
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• 2008

Three kinds of hydroxypropyl cellulose (HPC) derivatives: 6- (cholesteryloxycarbonyl) pentoxypropyl celluloses(CHPCs) with degree of esterification(DE) ranging from 0.6 to 3, 6-[4-{4'-(nitrophenylazo)phenoxycarbonyl}] pentoxypropyl celluloses (NHPCs) with DE ranging from 0.4 to 3, and fully 6-(cholesteryloxycarbonyl) pentanoated NHPCs (CNHPCs) were synthesized, and their thermotropic liquid crystalline properties were investigated. All the CHPCs and NHPCs with $DE{\leq}1.7$ formed enantiotropic cholesteric phases, whereas CNHPCs with 6-(cholesteryloxycarbonyl) pentanoyl DE(DEC) more than 1.6 exhibited monotropic cholesteric phases. On the other hand, NHPCs with $DE{\geq}2.4$ and CNHPCs with $DEC{\leq}1.3$ showed monotropic nematic phases. NHPCs with $DE{\leq}l$, as well as HPC, formed right-handed helices whose optical pitches (${{\lambda}_m}'s$) increase with temperature, while all the CHPCs formed left-handed helices whose ${{\lambda}_m}'s$ decrease with temperature. In contrast with these derivatives, NHPCs with $1.4{\leq}DE{\leq}1.7$ and CNHPCs with $DEC{\geq}1.6$ did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cellulose chain and the cholesteryl group highly depends on the chemical structure and DE of mesogenic group.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1381-1382
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• 2008

Cholesteric Blue phase (ChBP) is constructed by the regular arrangement of the double helix, whereas the Smectic Blue phase (SmBP) has the inter-connected multi-lamellar structure. Orientation fluctuations of polymer stabilized ChBP and spontaneously super-cooled SmBP are discussed. Spatial topology of the defects play key role on the dynamic properties.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.2
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• pp.50-55
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• 1990

Flaws in GFRP(Glass Fiber Reinforced Plastics) were thermally detected using cholesteric liquid crystals. Presence of flaws changes the thermal conductivity of GFRP, and disturbs heat flow. When a uniform heat source is applied, the surface temperature of flawed region is different from that of sound region. The surface temperature distributions were measured by thermo-optic properties of liquid crystal. Since the colors of liquid crystal indicate temperature distribution of GFRP surface, the thermal disturbance by flaws could be detected. The locations of flaws in GFRP could be determined from the distribution of liquid crystal colors.

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.234-235
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• 2001

No Abstract.See Full-text

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.26-26
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• 2002

Cholesteryl 2,4-dichlorobenzoate의 결정은 두가지 서로 다른 결정구조로 결정화한다. Dichloromethane 용매에서 키운 결정(1)과 hexane 용매에서 키운 결정(2)이 서로 다른 구조를 나타낸다. Cholesterol O(3)에 결합한 dichloro- benzoate의 상대적인 배열도 이 두가지 구조에서 서로 다르다. 특히 이들 결정구조들은, 공간군(P2₁2₁2₁)과 격자상수들이 매우 비슷한 결정이다. 결정(1)은 뚜렷한 layer structure를 보여준다. 결정(1)은 예측한 대로 liquid crystalline state(cholesteric phase)가 130.8℃에서 나타내고 녹는점은 132.5℃이다. 결정(2)의 녹는점은 133.7℃이다.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.681-682
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• 2009

We fabricated a stressed liquid crystal cell by mixing liquid crystal with a photo-polymer. By carefully choosing the mixing ratio between liquid crystal and the polymer, and by suitable mechanical shearing of the substrates, we demonstrated feasible electro optical properties for displays.

• Journal of Information Display
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• v.2 no.4
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• pp.15-18
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• 2001

We report simple techniques to manufacture low-powered, high-resolution, reflective cholesteric displays using flexible plastic substrates. We use wax transfer printing to replace photo-lithography and incorporate polymer walls to increase the mechanical strength and lifetime of the displays. These printing methods can easily be adapted to roll-to-roll production.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.935-937
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• 2009