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1.
丁酸壳聚糖液晶的临界行为研究 总被引:6,自引:3,他引:6
用偏光显微镜法测定了丁酸壳聚糖在四种酸性溶剂中的临界浓度值.发现临界浓度值(v/v%)与溶剂的酸性无关,都是16%~17%.在以二氯乙酸为溶剂时,不同丁酰化程度的丁酸壳聚糖有相同的临界浓度.用DSC法测定了丁酸壳聚糖/二氯乙酸体系的临界温度,并绘制了相图.结果表明,浓度达60%(w/w%)后,临界温度基本不再变化,稳定在39℃左右. 相似文献
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甲壳素溶致液晶的研究 总被引:5,自引:0,他引:5
报道了甲壳素有溶致液晶性.对四种不同分子量的甲壳素的研究结果表明,分子量增大,临界浓度显著降低,胆甾相平均螺距减少,但液晶有序微区平均尺寸却增加.甲壳素分子量为284×106、147×106、94×105和53×105时,在二氯乙酸中的临界浓度(W/W)分别为0005、0015、0035和0050.根据理论分析,甲壳素可视为刚性链,与多肽相似.甲壳素的指纹状织构不同于其他溶致液晶体系,在各种分子量甲壳素的两相共存浓度区内,液晶有序存在于内含指纹的不规则微区内,而不是滴状微区内. 相似文献
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壳聚糖在二氯乙酸中的溶致液晶性 总被引:6,自引:0,他引:6
制备了不同脱乙酰度和分子量在1-3 ~15-1 ×105 范围内的壳聚糖样品,并用傅里叶变换红外光谱法(FTIR)和粘度法进行了表征.借助偏光显微镜研究了不同壳聚糖样品在二氯乙酸中的液晶相转变和液晶状态.实验结果表明,分子量在105 ~106 范围内的增大使壳聚糖形成液晶相的临界浓度( C* ) 略有降低;脱乙酰度在70 ~90 % 范围内,对C* 的影响基本可以忽略.临界浓度的实验值与根据Khokhlov Semenov Odijk 理论预示的值比较一致,说明蠕虫链模型可以很好地描述壳聚糖分子链在二氯乙酸中的溶致液晶行为. 相似文献
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Yan-ming Dong Jian-wei Wang Qing Yuan Department of Materials Science Xiamen University Xiamen China 《高分子科学》2000,(1):15-17
The critical concentration of lyotropic liquid crystalline phase transition for chitin derivatives was determinedusing a polarization microscope. The influence of molecular weight on critical concentration of liquid crystalline solution forchitin, chitosan, cyanoethyl chitosan and propionyl chitin successively increases as the chain rigidity decreases. Therefore itcan be used as an indicator of the chain rigidity. 相似文献
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Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than tensolvents were determined using both Abbe refractometer and polarized microscopy. Criti-cal concentration C_(crit) of forming liquid crystal phase decreased with increasing solubilityparameter δ of solvent until approaching the δ of polymer. Although the alcohols usedas solvents had the same variation rule, the critical concentration values of their solutionswere much higher, due to their excessive large hydrogen bond component of δ. The experi-ments of using mixed solvents which showed good linear relation between C_(crit) and δ alsoproved this rule. A technique of Transmission Optical Analysis was first used to estimatethe concentration dependence of critical phase transition temperature T_(crit) of EC, and aT-C phase diagram could be drawn. 相似文献
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甲壳素类液晶高分子研究--低分子量壳聚糖溶致液晶性及分子量对液晶临界浓度的影响 总被引:3,自引:0,他引:3
研究了两种用酶降解法得到的低分子量壳聚糖样品(CS1和CS2)的溶致液晶性.用GPC并辅以质谱法确定了两样品的数均相对分子质量为622和2311 g/mol.在相对分子质量低至622的低分子量壳聚糖(相当于四糖)水溶液中仍发现了溶致液晶现象,并确定出相对分子质量为622和2311的低分子量壳聚糖液晶临界浓度为73%和36%(W/W%),这些结果与已报道的中、高分子量壳聚糖液晶临界浓度随分子量升高而降低的基本规律是一致的.实验结果与经典的KS理论预测值不符,因为低分子量壳聚糖的相对分子质量超过了KS理论对高分子临界浓度的预测范围. 相似文献
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Yan-ming Dong Yu-song Wu Mian Wang Department of Materials Science & State Key Laboratory for Physical Chemistry of Solid Surfaces Xiamen University Xiamen China 《高分子科学》2001,(3):247-253
The cholesteric liquid crystalline structure in chitosan/polyacrylic acid composite films was studied by surfacetechniques. A periodical lamellar-like structure was observed in the permanganic acid etched film sufface by both scanningelectron microscopy (SEM) and atomic force microscopy (AFM), instead of the thumb-print texture which can be detectedwith polarized optical microscopy. It is suggested that the periodical lamellar-like structure is induced by the etchingselectivity between cholesteric layers due to different molecular arrangement on the film surface. Four kinds of perpendiculardisclinations, i.e. χ→τ→λ~+, χ→λ+τ~+, χ→τ+τ~+ and χ→λ~- +λ~+, were found in the composite films from SEMobservations. The smallest periodicity of lamellar-like structure (equals to half pitch) is 20~40 nm measured with AFM. 相似文献
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A thermotropic liquid crystal copolyester resin based on p-hydroxybenzoic acid, 2, 6-naphthoic acid, hydroxyquinone and PET was synthesized by melt condensation and studied. The results based on DSC and X-ray diffraction indicated that there were a rapid and a slow crystallization processes for the copolyester at certain conditions. A critical temperature was suggested, below which the slow crystallization could hardly happen. Above the critical temperature the extent of the slow crystallization process depended not only on annealing temperature but also on the annealing time. A fine crystal structure with high melting point and narrow diffraction peak was formed under favorable conditions. 相似文献
10.
A series of aromatic-aliphatic copolyamides containing different aliphatic diamine units was synthesized by low temperature solution polycondensation. The liquid crystalline critical concentration (c*) and liquid crystalline critical temperature (T*) of these copolyamides exhibited an odd-even zigzag effect with the odd-even variation of carbon atom number in the aliphatic dimes used. 相似文献
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合成了氮上完全取代的邻苯二甲酰化壳聚糖 (PhthCS) .用DSC研究了PhthCS DMSO液晶溶液的热致相转变 .偏光显微镜和DSC测定都表明临界浓度为 43wt% .在浓度高于 43wt%的溶液的DSC曲线中观察到了除了液晶 各向同性液体转变 (清亮点 )外还有一个明显的凝胶 溶胶转变 .凝胶 溶胶转变温度和转变焓均比文献报道的不规则取代的N 邻苯二甲酰化 O 乙酰化壳聚糖大得多 ,可见取代的规整性对凝胶 溶较转变有很大的影响 .根据DSC研究结果绘制了PhthCS DMSO体系的相图 相似文献
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本文用折射率法研究了氰乙基纤维素在二甲基甲酰胺和二甲基亚砜中形成溶致性液晶的过程,测定了临界浓度C_1~*和C_2~*。对用该方法研究高聚物液晶溶液的有效性以及折射率与其浓度和溶液结构的关系进行了探讨。讨论了各种情况下的n—C曲线。 相似文献
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Dilute solution behavior of chitosan was studied in formic acid, acetic acid, lactic acid andhydrochloric acid aqueous solution under different pH values. The reduced viscosities, η_(sp)/C,ofchitosan solutions were dependent on the properties of acid and pH value of solvents. For a givenchitosan concentration, η~(sp)/C decreased with the increase of acid concentration, or decreasing pHof solvent, indicating shielding effect of excessive acid similar to adding salt into solution. Thestabilities of dilute chitosan solution in formic acid and lactic acid were better than that in acetic acid and hvdrochloric acid. 相似文献
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Ethyl-cyanoethyl cellulose [(E-CE)C]/cross-linked polyacrylic acid [PAA] molecular compositeswith cholesteric order were prepared. It was found that the macromolecular cholesteric structure was changedwith the swelling of PAA in the composites. The selective reflection of the cholesteric phase shifted to thelonger wavelength and the X-ray diffraction angle shifted to the high angle direction during swelling, whichsuggested that the cholesteric pitch and the number of the layers of ordered (E-CE)C chains in the cholestericphase were increased. 相似文献
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A novel palladium-coordinating Azo-type liquid crystalline polysiloxane (Pd-AZLCP) has been synthesized by chelation reaction of polymeric ligand, Azo-type liquid crystalline polysiloxane(AZLCP), with palladium dichloride and potassium chloride in the presence of tetrahydrofuran (THF) as reaction medium instead of dioxane/water system, which has been used since Cope first reported the synthesis of palladium-azobenzene in 1965 . The mesogenic behaviors examined by DSC, temperature-variable X-ray diffraction and polarizing microscopy indicate that the incorporation of Pd ions into the liquid crystal polymer can play a positive effect on the mesogenic property of the parent polymeric ligand. It is exhibited that the isotropization temperature T_i is increased and the mesophase range ΔT has been widened, too. 相似文献
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The synthesis and phase behaviour of chiral combined main/side chain liquid crystallinecopolymers containing pendant group constituted by chiral side group and trans-azobenzenemoiety with nitro end group are described. The formation of liquid crystalline polymorphism ofcopolymers is influenced by various contents of achiral side group. 相似文献
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A series of novel mesogenic polyamides containing a flexible pendent side group wassynthesized by solution condensation polymerization. The new monomers, diacids and di-amines containing flexible elements of diferent lengths, were also synthesized and character-ized by ~1HNMR, mass spectroscopy and elemental analysis. The polymers were character-ized by viscosity measurements, differential scanning calorimetry (DSC), X-ray diffiactionand polarizing optical microscopy These studies revealed that polyamides containingflexible elements of a sufficient length exhibited thermotropic liquid crystalline(LC) pro-perties. The melting temperatures of this series of polymers were particularly sensitive tothe length of the flexible segment on the main chain and that of the flexible pendent esterside chain. Lyotropic LC behaviours were also observed in solution. 相似文献
20.
Qi-ding Mi Qi-feng Zhou Department of Polymer Science & Engineering College of Chemistry Peking University Beijing China 《高分子科学》2000,(2):139-148
Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, andmesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of thesepolymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Theirliquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. Theresults show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2)a flexible spacer will decrease the "Jacket Effect" and the liquid crystallinity and 3) a subtle modification of the terminalgroups on the mesogenic unit may also have a significant influence on properties of the polymers. 相似文献