• Polymer(Korea)
• /
• v.37 no.3
• /
• pp.276-287
• /
• 2013

Two kinds of N,O-hydroxypropyl chitosans (HPCTOs) with degree of substitution (DS) and molar substitution (MS) ranging from 2.15 to 2.39 and 2.9 to 4.1, respectively, and five kinds of aliphatic acid esters of HPCTOs (HPCTOAms, m=0,2,4,7,9, the number of methylene units in aliphatic substituent) based on the HPCTOs were synthesized, and the thermotropic liquid crystalline properties of the derivatives were investigated. All the derivatives formed enantiotropic cholesteric phases whose optical pitches (${\lambda}_m$'s) increased with increasing temperature. However, the glass and clearing temperatures, the magnitude of ${\lambda}_m$ of the mesophase at the same temperature, and the temperature dependence of ${\lambda}_m$ of the investigated derivatives highly depended on MS and m. The thermotropic mesophase properties of HPCTOAms were significantly different from those reported for the aliphatic acid esters of hydroxypropyl celluloses. The results indicate that the secondary amino group in the C-2 position plays an important role in the thermal stabilization and temperature dependence of ${\lambda}_m$ of the cholesteric mesophase.

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

• Polymer(Korea)
• /
• v.31 no.1
• /
• pp.58-67
• /
• 2007

Fully cholesteryloxycarbonated and (8-cholesteryloxycarbonyl) heptanoated disaccharide derivatives were synthesized by reacting cellobiose, maltose, and lactose with cholesteryl chloroformate or 8- cholesteryloxycarbonylheptanoyl chloride, and their thermotropic liquid crystalline properties were investigated. All the cholesteryloxycarbonated derivatives (CH1DSs) formed enantiotropic cholesteric phases, whereas all the (8-cholesteryloxycarbonyl) heptanoated derivatives (CH8DSs) exhibited monotropic cholesteric phases with left-handed helicoidal structures whose optical pitches (${\lambda}m's$) decrease with increasing temperature. All the CH1DSs, contrast with the CH8DSs, did not display reflection colors over the full cholesteric range, suggesting that the helicoidal twisting power of the cholesteryl group highly depends on the length of the spacer joining the cholesteryl group to the disaccharide chain. The thermal stability and degree of order in the mesophase and the temperature dependence of the ${\lambda}m$ observed for EH8DSs were entirely different from those reported for the cholesterol-bearing dimers and triplet and the (8-cholesteryloxycarbonyl) heptanoated polysaccharide derivatives. The results were discussed in terms of the difference in the number of the mesogenic units per mole of repeating unit and the flexibility of the main chain.

• Polymer(Korea)
• /
• v.31 no.4
• /
• pp.356-367
• /
• 2007

Three kinds of amylose derivatives such as: cholesteryloxycarbonated amyloses(CAMs) with degree of esterification(DE) ranging from 1.8 to 3, (6-cholesteryloxycarbonyl)pentanoated amyloses(PAMs) with DE ranging from 0.3 to 3, and fully cholesteryloxycarbonated PAMs(CPAMs) were synthesized, and their thermotropic liquid crystalline properties were investigated. CAMs with $DE{\geq}2.6$, PAM with DE=1.6 and all the CPAMs formed enantiotropic cholesteric phases, whereas PAM with $DE{\geq}2.2$ exhibited monotropic cholesteric phases. PAM with $DE{\geq}2.2$ and CPAMs with (6-cholesteryloxycarbonyl)pentanoyl DE (DS) more than 1.0 formed cholesteric phases with left-handed helical structures whose optical pitches (${\lambda}_{m'}s$) decrease with increasing temperature. However, the ${\lambda}_{m'}s$ of these samples decreased with increasing DS at the same temperature. On the other hand, CAMs, PAM with DE=1.6, and CPAM with DS=0.3 did not display reflection colors over the full cholesteric range, suggesting that the helicoidal twisting power of the cholesteryl group highly depends on the length of the spacer joining the cholesteryl group to the main chain and DS. The thermal stability and degree of order in the mesophase observed for the amylose derivatives highly depended on DE or DS. The results were discussed in terms of the difference ul the hydrogen bond, the internal plasticization, and the decoupling of the motion of side group with the main chain.

• Polymer(Korea)
• /
• v.32 no.5
• /
• pp.446-457
• /
• 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)
• /
• v.32 no.5
• /
• pp.489-496
• /
• 2008

The thermotropic liquid crystalline behavior of a homologous series of poly[1-{4-(4' nitrophenylazo) phenoxycarbonylalkanoyloxy}ethylene]s (NAPEn, n = $2{\sim}8$,10, the number of methylene units in the spacer) have been investigated. All of the homologues formed monotropic nematic phases. The glass transition temperatures decreased with n. This is attributed to a plasticization of the backbone by the side chains. The isotropic-nematic phase transition temperatures decreased with increasing n up to 7 and showed the odd-even effect. However it became almost constant when n is more than 7. This behavior was 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 entropic gain for the clearing transition. The mesophase properties of NAPEn were entirely different from those reported for the polymers in which the azobenzene groups are attached to polyacrylate, polymathacrylate, and polystyrene backbones through polymethylene spacers. The results indicate that the mode of chemical linkage of the side group with the main chain plays an important role in the formation, stabilization, and type of mesophase.

• The Korean Journal of Rheology
• /
• v.2 no.2
• /
• pp.56-65
• /
• 1990

열방성 액정고분자와 폴리카보네이트를 대상 수지로 하여 용융혼합기로 액정고분자 의 함량, 혼합속도 및 온도등의 변환에 따른 훈련 특성을 측정하고 고분자 혼합물의 혼련조 건과 유변학적 특성 모폴로지 사이의 관계를 조사하였다. 혼련 토크는 100rpm의 혼합속도 에서 극소값을 보이며 혼합기 내의 전단속도가 낮기 때문에 혼력에의해서는 LCP가 섬유상 으로 형성되지 못하고 구형의 입자로 존재함을 알수 있었다. 혼합물의 점도는 시험된 전단 속도 영역에서 순수한 고분자보다 현저히 낮으며 5wt%의 소량 첨가로도 5배의 점도 감소 효과를 보이고 LCP함량이 약 30wt%일 경우 점도 및 혼합에너지가 최소로 되었다. Capillary 레오미터의 실험결과 LCP/PC의 점도비가 1보다 작거나 같튼 전단장하에서 LCP 는 섬유상을 형성하였으며 높은 점도비의 경우 LCP의 변형이 어려워 구형의 입자로 존재하 였다. 또한 혼합물의 PC Tg 이동은 에스터르 교환 반응에 의한 부분적인 혼화성의 증가에 기인함을 알수 있었다.

• Textile Coloration and Finishing
• /
• v.2 no.4
• /
• pp.245-250
• /
• 1990

Copolyspiroacetals were synthesized by interfacial polycondensation from 3, 9-bis(4-hydroxyphenyl)-2, 4, 8, 10-tetraoxaspiroundecane(SAB) and 4, 4'-biphenol(BP) with sebacoyl chloride. These copolymers were soluble in polar solvent such as phenol/tetrachloroethane and sulfuric acid, and exibited good thermal stability. But they did not exhibit thermotropic mesophases. The structures of spiroacetal moiety were observed by computer-aided-modeling that had two types of conformational isomers and not linear and/or not planar conformations.

• The Korean Journal of Rheology
• /
• v.6 no.2
• /
• pp.96-103
• /
• 1994

열방성 액정 고분자인 백트라와 폴리페닐렌 설파이드와의 블렌드를 주사전자현미경, 시차주사 열분석기, 그리고 모세관 레오미터를 이용하여 전 조성 범위에 대하여 연구하였다. 블렌드의 결정화와 용융에 관한연구결과로부터 두 고분자 사이에는 상호작용이 없음을 알수 있다. 이는 두 개의 상이 완전히 분리되기 때문이다. 폴리페닐렌설파이드를 많이 포함하고 있는 블렌드의 점도는 상당히 감소되었으며 이는 높은 전단속도에서 열방성 액정 고분자가 섬유구조를 갖기 때문이다. 열방성 액정고분자의 섬유구조는 열방성 액정 고분자가 섬유구 조를 갖기 때문이다. 열방성 액정 고분자의 섬유구조는 열방성 액정 고분자와 등방성상과의 점도비와 전단속도에 의해 영향을 받음을 알수 있다.

• Applied Chemistry for Engineering
• /
• v.8 no.1
• /
• pp.49-58
• /
• 1997

LCP/PA alloy was prepared by blending poly(${\varepsilon}-caprolactam$) (PA) with liquid crystal polyester, Vectra (LCP) having high elasticity and strength. The alloy prepared amorphous PA with more than 10 parts of thermotropic LCP had poor compatibility. To increase the compatibility of the alloy, compatibilizing agent, poly(glycinylmaleimide-co-methylmetacrylate)[poly(GMI-co-MMA)] copolymer was prepared by copolymerizing N-glycinylmaleimide(GMI) with methylmetacrylate(MMA). And then, it was blended with LCP and PA to produce LCP/PA alloy having an excellent compatibility. The compatibility characteristics of the alloy prepared from LCP and PA using the poly(GMI-co-MMA) was determined by measuring the thermal characteristics of glass transition temperature of nematic LCP, and rheological properties, and also high rate impact and flexual characteristics of the alloy were determined.