• Polymer(Korea)
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• v.25 no.2
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• pp.279-292
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• 2001

Two kinds of (hydroxypropyl)cellulose(HPCs) with different molar substitution (MS) and three types of derivatives based on the HPCs: (acetoxypropyl)celluloses, (ethoxypropyl)celluloses, and (cyanoethoxyprofyl)celluloses were synthesized, and their thermal and mesomorphic properties were investigated. All samples, which exhibit cholesteric reflection colours at room temperature, formed right-handed helicoidal structures whose optical pitches (λ$_{ms}$ ) increase with temperature. However, the isotropization ($T_{i}$) and glass temperatures, the magnitude of λ$_{m}$ of the mesophase at the same temperature, and the temperature dependence of λ$_{m}$ of the investigated derivatives highly depended on MS and the length and structure of the side chain introduced in HPC. The results were discussed in terms of the difference in the polarity and flexibility of the substituents and the distance between the main chains. For all derivatives, Am values approached infinity at temperatures above the $T_{i}$, of the mesophase, and no reversal in the sense of the pitch with temperature was detected.

• Polymer(Korea)
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• v.28 no.1
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• pp.92-102
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• 2004

(6-Cholesteryloxycarbonylpentoxypropyl)celluloses (CHPCs) with degree of esterification (DE) ranging from 2.25 to 2.91 were synthesized by reacting hydroxypropyl cellulose with 6-cholesteryloxycarbonylpentanoyl chloride. The acrylic esters of CHPCs (CHPCEs) and their photocrosslinked films with liquidcrystalline order were also synthesized. The thermotropic properties of mesophase for both uncrosslinked and crosslinked samples and the swelling behavior of the crosslinked samples in acetone were investigated. The hydroxypropyl cellulose exhibited an enantiotropic cholesteric phas, while all the uncrosslinked cholesterylbearing samples exhibited a monotropic cholesteric phases; the 6-cholesteryloxycarbonylpentanoyl chloride also showed a monotropic smectic phase. The hydroxypropyl cellulose formed a right-handed helix whose optical pitch (λ$\sub$m/) increases with temperature, whereas all the uncrosslinked derivatives farmed left-handed helices whose λ$\sub$m/'s decreased with temperature. The thermal stability of the mesophase and the magnitude of λ$\sub$m/ at the same temperature for both CHPCs and CHPCEs decreased with increasing DE. All the crosslinked samples, in constrast with CHPCEs, did not display reflection colors but exhibited an anisotropic swelling characteristic of crosslinked gel retaining liquid-crystalline order.

• 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.

• Polymer(Korea)
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• v.36 no.1
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• pp.76-87
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• 2012

Three kinds of hydroxypropyl cellulose (HPC) derivatives, [6-{4-(4-cyanophenylazo)phenoxy}]hexyloxypropyl celluloses (CAHPCs) with degree of etherification (DET) ranging from 0.4 to 3, fully substituted acrylic acid esters of HPC (HPCA) and CAHPCs (CAHPCAs) were synthesized. The crosslinked HPCA (HPCAG) and CAHPCAs (CAHPCAGs) were also prepared by exposing thermotropic mesophases of HPCA and CAHPCAs to UV light. Both CAHPCs and CAHPCAs with DET ${\leq}$ 1.2, as well as HPC and HPCA, formed enantiotropic cholesteric phases whose optical pitches(${\lambda}_m$'s) increase with temperature, wheras both CAHPCs and CAHPCAs with DET ${\geq}$ 1.4 showed monotropic nematic phases. CAHPCAGs with DET ${\leq}$ 1.2, as well as CAHPCAs with DET ${\leq}$ 1.2, exhibited reflection colors in a wide temperature range. On the other hand, CAHPCAGs with DET ${\geq}$ 1.4, as well as CAHPCAs with DET ${\geq}$ 1.4, showed Schileren textures typical of nematic phase, indicating that the liquid crystalline structure is virtually locked upon photocrosslinking. The isotropization temperatures($T_i$'s) of both CAHPCAs and CAHPCAGs decreased with increasing DET. The $T_i$ of CAHPCAG, however, was higher than that of CAHPCA at the same DET. Moreover, the temperature dependence of ${\lambda}_m$ of CAHPCAGs was much weaker than that of CAHPCAs.

• Polymer(Korea)
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• v.36 no.3
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• pp.380-392
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• 2012

Four kinds of N,O-hydroxypropyl chitosans (HPCTOs) with degree of substitution(DS) and molar substitution (MS) ranging from 2.47 to 2.52 and 4.9 to 7.8, respectively were synthesized, and their molecular chracteristics and thermotropic and lyotropic liquid crystalline properties were investigated. MS was exceedingly larger than DS, showing that in the later stages of reaction, propylene oxide was preferentially added to the side chains rather than the main chain. All the derivatives formed thermotropic cholesteric phases. The glass and clearing temperatures were decreased with increasing MS. The optical pitches (${\lambda}_m$'s) of the thermotropic cholesteric phases increased with temperature. However, the ${\lambda}_m$'s of the derivatives at the same temperature increased with increasing MS. Solutions of HPCTOs in water, methanol, ethanol, acetic acid, and formic acid containing more than 30 wt% polymer also formed cholesteic phases whose ${\lambda}_m$'s decreased exponentially with increasing polymer concentration. The concentration dependence of ${\lambda}_m$ of HPCTO solutions, however, highly depended on the nature of the solvent and MS. The thermotropic and lyotropic mesophase properties of HPCTOs were significantly different from those reported for hydroxypropyl celluloses. The results indicate that the secondary amino group in the C-2 position plays an important role on the formation, stabilization, and temperature and concentration dependencies of ${\lambda}_m$ of the cholesteric mesophase.