壳聚糖/二氯乙酸溶致液晶的热致相转变

关于壳聚糖及其各种衍生物的溶致液晶的研究已有报道^[13],但尚未见到有关壳聚糖/有机酸液晶溶液的热致相转变的报道.本文研究了壳聚糖/二氯乙酸液晶溶液的相转变,并探讨了该体系的相转变机理.     

NUCLEATION ACTION OF THERMOTROPIC LIQUID CRYSTAL POLYMERS IN THE BLENDS WITH PET

The present work concerns the crystallization of PET accelerated by addition of thermotropic liquid crystalline polymers (TLCP)based on two aromatic copolyesters: PHB/PET (60:40 ) and PHB/HDA/2,6-DNA /IPA ( 50:25 : 12.5 : 12.5 ). The investigation has been made by measurements of the cold-crystallization and melt-crystallization temperatures by DSC and of the changes of density and depolarizing light intensity during the isothermal process. In addition, the morphology of selectively etched surface of compressing pellets proved the presence of crystalline fibrillar structure, it can be supposed to have grown up from the micelle nucleus based on bundle of rigid TLCP chains.     

Morphology and physical properties of a liquid–crystalline main-chain polymer with flexible side chains

A molecular laminate model is used to explain the properties of unoriented and oriented films of poly(p-phenylene-2,5-didodecyloxyterephthalate) cast from solution. In oriented films the two different crystal modifications, A and B, give rise to room temperature tensile moduli of 15 and 30 GPa respectively. The packing (in clusters) of the side chains in modification A, leading to a glass–like transition in the side-chain regions around ?40°C, is largely responsible for this difference. Oriented films of modification A and B have coefficients of thermal expansion of +0.3×10^?5 and ?1× 10^?5 K^?1 respectively. It is concluded that the properties of this class of polymers can be adjusted in a systematic way.     

Liquid crystals of disc-like molecules

Thermotropic mesomorphism has been observed in pure compounds consisting of simple disc-like molecules, viz., benzene-hexa-n-alkanoates. Thermodynamic, optical and x-ray studies indicate that the mesophase is a highly ordered lamellar type of liquid crystal. Based on the x-ray data, a structure is proposed in which the discs are stacked one on top of the other in columns that constitute a hexagonal arrangement, but the spacing between the discs in each column is irregular. Thus the structure has translational periodicity in two dimensions and liquid-like disorder in the third.     

热致液晶聚酰胺的溶解性能和热性能

采用直接缩聚法,用自制的新型二元酸PEG3与芳香二胺进行缩聚反应,合成出较高分子量(比浓对数粘度为1.063 dL/g)的热致液晶聚酰胺,对其热性能和溶解性能进行了研究。结果表明,柔性链的引入,降低了聚酰胺的熔点(Tm=307.8℃),有利于液晶相的形成。而苯环的引入,平均分配了聚酰胺的刚性,既保持了聚酰胺耐热的特性,又提高了液晶相的稳定性(液晶显示范围ΔT=Ti-Tm=66.1℃),有利于该液晶高分子的应用。热失重(TGA)曲线显示了合成的聚酰胺具有较好的热稳定性(温度在400℃以上的质量损失为5%)。合成的聚酰胺具有较强的耐溶剂性,不溶于非极性溶剂,只能部分地溶解于强极性的纯溶剂或溶解于加盐(LiCl,或CaCl2)的复合溶剂中。     

热致性液晶共聚酯的拉伸流动行为

采用入口收缩流动的实验方法研究了改性PET/ 80PHB液晶共聚酯LCP80的拉伸流动行为 ,考察了拉伸速率、温度等对其拉伸粘度、Trouton比的影响 .实验结果表明 ,LCP80的入口压降值很大 ,其中由拉伸引起的入口压降是主要的 .在该文实验条件下LCP80均表现出拉伸稀化现象 ,并且Trouton比值都远大于 3 .根据流动中液晶织态结构的变化解释了实验现象 ,并对入口收缩流动的实验数据处理方法作了改进 ,比Beery的方法更为合理 ,也具有更广的适用性 .     

Mesomorphic properties and orientational order parameter of 4-pentyl cyclohexyl-4-(4-propyl cyclohexyl) benzoate from X-ray diffraction studies

The mesogen 4-pentyI cyclohexyl-4-(4-propyl cyclohexyl) benzoate, molecular formula C₂₇H₄₂O₂, has been investigated at different temperatures using X-ray and texture studies. For X-ray studies an arrangement for taking X-ray photographs at different temperatures has been designed and fabricated. In addition to the nematic phase the mesogen exhibits two smectic phases. On the basis of microscopic investigation and X-ray studies the two smectic phases exhibited have been identified as the SmE and SmB phases. From X-ray patterns, the average intermolecular distances and apparent molecular length/layer thickness for the different mesomorphic phases have been determined as a function of temperature. Orientational order parameters (P2) and (P4) of the sample ordered by a magnetic field have been determined in the SmB phase.     

Thermotropic Poly(Ester-Amides) Based on Naphthalene Monomers

The structure and properties of a range of thermotropic poly(ester-amides) derived from 2,6-naphthalene derivatives is described. Many of these polymers may be melt-processed into fibers, monofils, and molded structures having very attractive physical and mechanical properties. A variety of monomers has been used and structure/composition/property relationships are described along with details of synthesis and processing conditions. Both fibers and molded articles may be heat-treated to enhance their tensile properties. Molded articles and extruded rods have exceptional tensile moduli in the unfilled state.     

热致性液晶聚合物的种类对液晶/环氧树脂共混物固化反应动力学的影响

采用等温DSC固化动力学研究方法,用自催化动力学模型对反应型热致性液晶聚合物/环氧树脂共混体系进行研究.结果表明,EP/DDS未改性体系,在α＜40%范围遵循自催化反应机理;EP/DDS/LCPU共混改性体系,在α＜60%范围遵循自催化动力学反应机理,而且自催化反应速率和非催化反应速率均大于未改性体系,表明反应型热致性液晶聚合物的活性基团对固化反应起到了催化促进作用;EP/DDS/PHBHT共混改性体系能够较好符合n级反应机理,固化反应的活化能较大,说明没有反应基团的液晶聚合物(PHBHT)对固化反应无明显促进作用.