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排序方式: 共有2935条查询结果,搜索用时 500 毫秒
31.
Peng Chen Jun Chen Baoqing Zhang Jun Zhang Jiasong He 《Journal of Polymer Science.Polymer Physics》2006,44(6):1020-1030
Polycarbonate (PC) was melt blended with small amount of liquid‐crystalline polymer (LCP) and various contents of glass beads (GB) having different diameters. The rheological measurements indicated that the GB addition increased the viscosity ratio and seemed unfavorable to the LCP fibrillation. However, the morphological observation showed that the LCP fibrillation was promoted by the GB addition and varied with the GB packing. With the increased GB packing by increasing the GB content and/or decreasing the GB diameter, LCP deformed from spheres and ellipsoids into stretched ellipsoids at lower shear rates and into long fibrils at higher shear rates. Although higher content of smaller GB jammed into the larger LCP droplets and inhibited the LCP fibrillation, very long LCP fibrils formed at higher shear rates at a high enough packing of GB. The relationship between GB packing and LCP fibrillation revealed two kinds of hydrodynamic effects of GB promoting the LCP fibrillation: at lower GB packing, the shear flow was enhanced by the high local shear between GB, in quantity; and for a high enough GB packing, the shear flow was changed, in quality, into elongational flow, which was more effective for the LCP fibrillation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1020–1030, 2006 相似文献
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A new series of acrylates with the same mesogens containing thioester as bridge-bondwere synthesized, and the acrylates were characterized by H~1 NMR, IR and MS. Thepolymers were obtained by radical polymerization using AIBN as initiator. The monomersand polymers exhibit thermotropic-enantiotropic liquid crystalline behavior. 相似文献
34.
二茂铁液晶因其独特的稳定性和易于衍生化受到研究人员的青睐[1- 8] 。我们曾经报道过一类单取代二茂铁液晶的合成与介晶性[9] 。这里我们报道另外一类二茂铁单取代液晶 ,并对分子的长度、溴原子取代对介晶性的影响进行探讨。合成路线如下 :1 实验部分BruckerACE -2 0 0spectrometer,CDCl3作溶剂。NicoletMagna-IR 5 0 0Spectrometer,SeriesⅡ ,KBr压片。WRS -IA ,CarloErba 1 1 0b。Perkin -Elmer 7Series热分析仪 ,分温速度 1 0℃ /mi… 相似文献
35.
Cheng-Fang Ou 《European Polymer Journal》2002,38(3):467-473
The crystallization characteristics of polypropylene (PP) and low ethylene content PP copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC). PP and PP copolymers was blended with three different kinds of co[poly(butylene terephthalate-p-oxybenzoate)] copolyesters, designated B28, B46, and B64, with the copolyester level varying from 5 to 15 wt.%. All samples were prepared by solution blending in hot xylene solvent at 50 °C. The crystallization behavior of samples was then studied by DSC. The results indicate that these three copolyesters accelerate the crystallization rate of PP and PP copolymers in a manner similar to that of a nucleating agent. The acceleration of crystallization rate was most pronounced in these blend systems with a maximum level at 5 wt.% of B28. The observed changes in crystallization behavior are explained by the effect of the composition and the amount of copolyester in the blends. 相似文献
36.
Edwin Weber Claus Wimmer Ingeborg Csöregh Olga Gallardo 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(2):141-153
A novel host molecule, 1, suitable for crystalline lattice-type inclusion, has been synthesized, and its cocrystal formation ability has been investigated. Host 1 proved to be of potential use for organic solvent separation and retrieval, and a promising auxiliary for solidification of certain odorous substances. The crystal structures of the solvent-free host 1, and its complex with 1,4-dioxane (1 : 1), have been determined by single crystal X-ray diffraction. The structure of 1 (guest-free) is triclinic, P
, with a = 9.452(2), b = 10.359(3), c = 13.116(3) Å, = 101.80(2), = 106.53(1) and = 104.32(1)°. The spacious, propeller-like molecules are held together by weak van der Waals' forces. The dioxane inclusion compound is monoclinic, P21/a, with a = 15.050(1), b = 8.641(1) and c = 20.658(1) Å, and = 94.56(1)°, and contains two crystallographically independent guest molecules, both located around symmetry centres. The molecular packing seems to be governed by C—H···O type bonds (C···O = 3.31 and 3.48 Å) from the host to the dioxane oxygens. 相似文献
37.
A series of ferrocene‐containing liquid‐crystalline polyphosphonates with an even number of methylene groups are reported. All the polymers gave birefringent melts. The mesophase was identified as transparent with an increase in the spacer. The effects of pendant substitution and the spacer were studied with thermogravimetric analysis and differential scanning calorimetry. The effects of the phosphonate group in the spacer and the ferrocene ester group in the mesogen were examined. The presence of a steplike mesogenic structure and a pendant phenyl group in the spacer led to reductions in the glass‐transition and melting temperatures. The ferrocene moiety in the mesogen might be one of the reasons for the increased thermal stability and decreased liquid crystallinity. An energy‐minimized structure for the mesogenic and spacer segments was created with computer‐modeling programs, and it suggested the reason for the reductions in the glass‐transition and melting temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2256–2263, 2002 相似文献
38.
PET-HBT嵌段热致性液晶共聚酯的合成 总被引:1,自引:0,他引:1
液晶高分子材料具有相当高的强度和模量,被誉为当代超级工程塑料.以对羟基苯甲酸甲酯、1,4-丁二醇为主要原料,经熔融酯交换合成双-对羟基苯甲酸丁二醇酯(BBHB);以四氯乙烷为溶剂,采用溶液缩聚法将过量的BBHB与对苯二甲酰氯(TPC)合成端基为BBHB的齐聚物(PHBT);以对苯二甲酸二甲酯与乙二醇为原料,经熔融酯交换合成对苯二甲酸双β-羟乙酯(BHET),然后采用溶液缩聚法将BHET与少量的TPC合成端基为TPC的齐聚物(PTET);最后以PHBT与PTET为原料,以四氯乙烷为溶剂,采用溶液缩聚法合成目标共聚酯(PET-HBT)。研究了共聚酯的双折射现象及热行为;用偏光显微镜观察了试共聚酯的织态结构并用FTIR表征了共聚酯的微观结构. 相似文献
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合成了9种具L-氨基酸衍生物结构的介晶化合物(I-Ⅲ,Ⅳab,Ⅴa,b,Ⅵa,b)、4种氨基酸衍生物(A1-4)和6种介晶化合物(M1-6).新化合物(Ⅰ-Ⅲ,Ⅳa,b,Ⅴa,b,Ⅵa,b,A4,M3-6)的化学结构通过IR、1HNMR和元素分析证实;并用偏光显微观察和DSC分析研究了其相变行为,结果表明有8种化合物(M3-6,Ⅵa,b,Ⅴb,Ⅵb)呈现液晶相变。测定了它们的比旋光度。通过X射线衍射研究了化合物Ⅵh120~130℃和Ⅵb170~180℃的近晶结构,Ⅵb显,Ⅵb呈。测定了化合物Ⅳb的电滞回线,证明其具铁电性。 相似文献