首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 421 毫秒
1.
液晶聚芳醚酮的结构与性能研究   总被引:1,自引:0,他引:1  
以联苯二酚、取代对苯二酚及含氟酮单体为原料 ,通过亲核取代反应 ,合成了系列具有液晶性的新型聚芳醚酮 .研究了聚合物分子结构与性能之间的关系 .由于结晶相是从有序的液晶相转化形成的 ,故侧基含量的增加对液晶聚合物的融熔转变温度无显著影响 .聚合物的液晶稳定性受侧基影响较大 ,含极性侧基的氯取代聚合物的液晶温区比含大空阻侧基的聚合物的液晶温区小得多 ,说明空间几何因素比极性因素对液晶稳定性的影响大 .不同分子量聚合物有不同的液晶有序结构 ,低分子量聚合物具有高有序液晶结构 ,而高分子量聚合物只有低有序的向列相结构 .  相似文献   

2.
《Liquid crystals》2012,39(12):1827-1842
ABSTRACT

It is a challenge to tailor the phase behavior and phase structure of side-chain liquid crystalline polymers carrying targeted ordered structures and functional properties. In this work, liquid crystalline (LC) properties of cholesterol side-chain polymers without spacer were controlled by molecular weight (Mn) and copolymerization. On the one hand, two series of homopolymers without the spacer, poly (methacrylic acid) cholesterol esters (PCholMCn) and poly (acrylic acid) cholesterol esters (PCholACn) with different Mn and low polydispersity, were achieved by reversible addition-fragmentation chain transfer polymerization. The experiment results indicated that the Mn had little effect on the LC properties of PCholMCn and all homopolymers formed the smectic A phase. However, the phase structures of PCholAC were found to be strongly Mn dependent. The polymers PCholACn were amorphous when the Mn was lower than a critical value of approximately 12103 g/mol. But when the Mn exceeded the critical value, the polymers exhibited smectic A phase. On the other hand, two kinds of random copolymers, poly(cholest-5-en-3-methacrylate)-co-polymethyl acrylate (PCholMC-co-MA) and poly(cholest-5-en-3-acrylate)-co-polymethyl acrylate (PCholAC-co-MA) were synthesized with various composition. The findings suggested that the steric effect of main-chain and the interaction of mesogens would promote the formation of LC phase.  相似文献   

3.
《Liquid crystals》1997,23(3):447-451
Using a radical copolymerization of 4-(4-cyanobiphenyl-4-yloxy)butyl acrylate and acrylic acid, a number of new liquid crystalline ionogenic copolymers capable of hydrogen bonding were synthesized. The formation of hydrogen bonds results in an invariant temperature interval of existence for the LC state (up to 52mol% of acrylic acid) and a rather sudden replacement of the nematic phase by the SmA phase with increase in content of acrylic acid ( 35 mol%) in copolymers.  相似文献   

4.
DU  Zhuwei  LU  Cuixiang  LI  Haoran  LI  Dingjie 《中国化学》2009,27(11):2237-2241
Hydrogels have been thought to be the material which can provide appealing replacements of biological organisms. Pores of hydrogels synthesized from lyotropic liquid crystalline (LLC) templates were smaller in size and more uniform than those of traditional hydrogels. LLC poly‐acrylamide (PAAm) hydrogels were used as the growth media of CaCO3. After copolymerized with acrylic acid and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), LLC hydrogels were modified with COOH and SO3H, respectively. The effect of functional groups on the biomimetic mineralization of CaCO3 was studied. Most of crystals from traditional hydrogels are rhombohedral and could not form aggregates. Only a few could aggregate and have a particular morphology with irregular orientation of subcrystal. Compared with crystals separated from traditional hydrogels, crystals growing in the LLC hydrogels were much more regulated and could form aggregates with particular morphology and regular orientation, that is, face (104) of rhombohedral subcrystals parallel to the surface of the macrocrystals. Modification of COOH and SO3H groups made CaCO3 subcrystal align more tightly. COOH had minor influences on the crystal orientation and small modification to the aggregate morphology. SO3H groups could change the crystal orientation and morphology effectively. The aggregates are pseudo‐spherical and the face perpendicularity to the face (104) parallels to the surface of the aggregates.  相似文献   

5.
聚芳醚酮与液晶聚酯多嵌段共聚物的合成表征   总被引:1,自引:0,他引:1  
近年来,以热塑性聚合物为基体,热致液晶聚合物(TLCP)作为增强剂的高分子原位复合材料由于其具有优异的机械性能和优良的成型加工性能,已引起各国工作者的普遍关注和极大兴趣.然而由于自聚集和相分离作用的影响,大部分液晶聚合物与通常的热塑性聚合物基体基本不相容或弱相容,这对于提高原位复合材料的力学性能不利.  相似文献   

6.
In this work we propose a new crosslinking agent and the method to use it for the synthesis of acrylate based hydrogels. The use of this diacrylate of glycerol, synthesized in our laboratory, allows the generation of materials with well defined micro‐structures in the dry state, unique meso‐ and macro‐structures during swelling, and enhanced mechanical properties and swelling capacity in water. These properties depend on the crosslinking agent concentration, as well as synthesis thermal history. Poly(acrylamide‐co‐acrylic acid) hydrogels are commonly crosslinked with N, N′‐methylenebisacrylamide or N‐isopropylacrylamide. Here we obtain and use a new crosslinking agent, obtained from the reaction between glycerol and acrylic acid to produce a Diacrylate of glycerol (DAG). Two synthesis methods at equivalent molar ratio of acrylamide/acrylic acid (AM/AA) were analyzed. The mechanical properties, the swelling capacity, and the morphology at microscale of these hydrogels showed a well defined transition at a critical concentration of crosslinking agent. DAG induces the generation of hydrogels with hierarchichal structure. The micro‐structure surface morphology was investigated by scanning electron microscopy, the meso‐structure by polarized light microscopy and the macro‐structure by CCD imaging. The hydrogels with hierarchical structures showed improved mechanical properties when compared with structureless hydrogels. Control of the microstructure allows the generation of materials for different applications, i.e. templates or smart materials that interact with electromagnetic radiation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2667–2679, 2008  相似文献   

7.
Random copolymers of poly(ethylene oxide) macromonomer with p‐vinylbenzyl end‐functional group (PEOVB) and liquid crystalline monomer, namely 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate (COA), were prepared by conventional free radical polymerization. A living anionic polymerization technique was employed for the synthesis of PEO macromonomers bearing p‐vinylbenzyl moiety at one end. The photon transmission method was also applied to study the phase transitions of COA monomer and its random copolymer with PEO. It was found that, for both samples, the nematic‐smectic A transition is continuous, but the critical fluctuation regions do not allow to obtain 3D XY values. Instead, we have obtained the values close to mean field regime. Scaling of thermal hystersis for random copolymer sample near the nematic‐isotropic transition was studied as well. Thermal hysteresis loops were produced under linearly varying temperature. It was shown that the areas of the hysteresis loops scale with the temperature scanning rate with an exponent being equal to 0.614 which is in good agreement with the field‐theoretical value.  相似文献   

8.
本文通过熔融酯交换和Schottern-Baumann缩聚反应合成了两类组成相同而序列结构不同的基于对羟基苯甲酸、对苯二甲酸和二元酚的三元共聚酯,用热台偏光显微镜、DSC和X-射线衍射,较详细地研究了序列结构对液晶相类型、转变温度和固态结构等的影响。结果表明,无规共聚酯较规则共聚酯的熔化温度普遍降低;但序列结构的差异并不改变液晶相类型,规则共聚酯和无规共聚酯均为热致向列型液晶,两类共聚酯固态结构的差异可用结构单元的相似性进行解释。  相似文献   

9.
Phase behaviour of hydrogen‐bonded multicomponent mixtures of bipyridine, dodecyloxybenzoic acid and dicarboxylic acids with poly(acrylic acid) were studied at different compositions and temperatures. It was found that in certain composition ranges, the mixtures form a homogeneous liquid crystalline phase of smectic type with an unusually high enthalpy of transition into the isotropic state. The nature of the anisotropic phase observed in the polymers is discussed. The phase behaviour was studied using IR spectroscopy, differential scanning calorimetry and X‐ray structure analysis.  相似文献   

10.
介绍了热固性丙烯酸酯液晶单体的合成路线、取向方式和聚合工艺,叙述了数种影响热固性丙烯酸酯液晶单体及其聚合物性能的主要因素,简要介绍了国内外热固性丙烯酸酯液晶研究的最新动向。  相似文献   

11.
The low-temperature copolymerization of N-vinylpyrrolidone with acrylic monomers (acrylic acid, acrylamide, and methyl acrylate) in vitrifying solutions in ethanol and DMF has been studied. It has been shown that the copolymerization proceeds after transition of preliminarily γ-irradiated at 77 K samples from the solid glassy state to a supercooled liquid. Experimental conditions that ensure formation of alternating and random block copolymers have been established. The composition of copolymers is determined by the relative mobility and initial ratio of comonomers in solution.  相似文献   

12.
研究了对象基苯甲酸(ABA)/聚对苯二甲酸乙二酯(PET)液晶共聚酯酰胺的晶体结构,以及热性能、流变学和力学性质。广角X射线衍射研究结果表明ABA链节的引入使PET的晶态结构发生畸变,但大部分结晶衍射峰仍然存在。随着ABA含量的增加,各晶面间距基本不变,微晶尺寸显著增大,结晶度急剧降低。差示扫描量热分析和热失重结果表明共聚酯胺具有优良的热稳定性,并且随着ABA含量的增加,共聚物的热稳定性提高,共聚  相似文献   

13.
甲壳型液晶高分子的发展很大程度上依赖于聚合物自组装的发展,而各种可设计、可预测、可调控的自组装策略的涌现,将甲壳型液晶高分子研究推向前所未有的高度,同时也极大地丰富了高分子化学与物理的内容,提升了研究水准.研究表明,侧链"甲壳效应"在调控甲壳型液晶高分子有序结构等方面有着重要作用.本综述从甲壳型液晶高分子设计合成、液晶相态调控、嵌段共聚物自组装和功能化应用等方面,总结和评述了近年来该领域国内的最新研究进展.最后,本综述总结了甲壳型液晶高分子在发展中所面临的主要问题,并对其发展趋势进行了展望.  相似文献   

14.
The influence of different amounts of anionic copolymers of N-Methyl N-vinyl acetamide (NMVA) and acrylic acid with various charge densities on the formation of the lamellar liquid crystal formed by sodium dodecyl sulfate (SDS)/decanol/water was investigated by means of polarization microscopy, small angle x-ray scattering (SAXS), transmission electron microscopy and rheology. On the contrary to the incorporation of poly(acrylic acid)  相似文献   

15.
Comb copolymers containing both hydrogenated and fluorinated side‐chains were prepared by copolymerization using acrylic or methacrylic monomers in several ratios. The crystal structures of these copolymers and layer structures of their organized molecular films were investigated by wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and out‐of plane X‐ray diffraction. Further, to selectively estimate the regularity of shorter fluorocarbon side‐chains, organized molecular films of copolymers were investigated by polarized near‐edge X‐ray adsorption fine structure (NEXAFS) spectroscopy. From the results of these measurements, it was inferred that these copolymers formed highly ordered layer structures, and a long spacing was predominantly determined by the arrangement of hydrogenated side‐chains, except in copolymers having extremely high fluorocarbon contents. In the case of the organized molecular films, the fluorinated side‐chains of methacrylate copolymers cannot form a highly ordered arrangement, whereas those of acrylate copolymers were oriented on monolayers. However, in both cases, the hydrogenated side‐chains predominantly formed layer structures in the organized films, and the fluorinated side‐chains did not contribute to the formation of the layer structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 534–546, 2008  相似文献   

16.
本文以苯甲酸对苯二酚酯双马来酰亚胺(Ia)和二苯醚二胺为单体,合成了Ia/二苯醚二胺的共聚物,应用FTIR谱、热分析DTA和DSC、热台偏光显微镜对共聚物的结构和液晶行为进行了研究。该类共聚物具有较好的热致液晶行为,其液晶相结构可以通过共聚物的化学交联反应而固定在交联网络中,从而形成液晶网络材料。  相似文献   

17.
The synthesis of liquid single crystal hydrogels (“LSCH”) in suitable molds offers an innovative concept to realize bifocal contact‐ or intraocular‐lenses. LSCH combine the properties required for applications as bifocal ophthalmic lenses: the soft and water‐containing hydrogel enables oxygen permeation and exhibits high birefringence due to the liquid crystalline phase structure built up by rigid rod‐like amphiphiles. Via a photo‐initiated crosslinking reaction of aqueous solutions of monomeric lyotropic liquid crystalline amphiphiles in the macroscopically ordered liquid crystalline state, we obtain optically uniaxially ordered and transparent LSCH. The orientation process and the phase structure of the anisotropic hydrogel is analyzed by deuterium NMR‐spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

18.
Soft tissues, such as fat and skin, present high flexibility and are capable of withstanding large deformation in various functions. Hydrogels that can resemble the mechanical performance of soft tissue are unique and widely demanded. In this study, micellar hydrogels based on biocompatible poly(l ‐glutamic acid) (PLGA) were designed with the enhanced capacity to bear large deformation. Amphipathic triblock copolymer poly(ethylene glycol) acrylate‐co‐poly(ε‐caprolactone)‐co‐poly (ethylene glycol) acrylate (APEG‐PCL‐APEG) with two terminal double bonds was synthesized and self‐assembled into micelles. At the same time, graft copolymers, poly(l ‐glutamic acid)‐g‐hydroxyethyl methacrylate (PLGA‐g‐HEMA) with double bonds were synthesized. APEG‐PCL‐APEG micelles and PLGA‐g‐HEMA were mixed to construct micellar hydrogel via radical polymerization. The crystalline structure and hydrophobic aggregation of copolymers (APEG‐PCL‐APEG) were found to associate with PCL molecular weight. Due to the hydrophobic stress dissipation and crystalline structure of the micelles, the softness and toughness of hydrogels were promoted, exhibiting a 25% increase in ultimate strain. Moreover, the micellar hydrogels were able to load proteins with long‐term retention. In addition, under dynamic mechanical stimulation, the release of proteins could be accelerated. Besides, the micellar hydrogels also supported rabbit adipose‐derived stem cells (rASCs) growth, thus exhibiting the potential toward soft tissue engineering. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1115–1125  相似文献   

19.
Ethyl-cyanoethyl cellulose [(E-CE)C]/acrylic acid (AA) becomes a cholesteric liquid crystalline solution withvivid colors when the (E-CE)C concentration is 42 wt%~52 wt%. (E-CE)C/polyacrylic acid (PAA) composites withcholesteric structure were prepared by polymerzing AA in (E-CE)C/AA liquid crystalline solutions. The layers of orderedpolymer chains in the cholesteric phase were inclined during polymerization and the degree of the inclination depended onthe polymerization temperature and the concentration of the solution before polymerization. The cholesteric structure in thecomposites could not be changed when temperature was lower than 100℃. Cross-linking of the PAA in compositesimproved their water-resistance. The cholesteric order of the composites without cross-linking was destroyed when theywhere immersed in water. The color derived from the selective reflection of the cholesteric phase of the cross-linkedcomposites turned from blue to red after the composites absorbed water. The color of the composites could be returned to theoriginal one when the absorbed water was removed from the swollen composites.  相似文献   

20.
Summary: The one step synthesis of a series of branched azobenzene side‐chain liquid‐crystalline copolymers by the self‐condensing vinyl copolymerization (SCVCP) of a methyl acrylic AB* inimer, 2‐(2‐bromoisobutyryloxy)ethyl methacrylate (BIEM), with the monomer 6‐(4‐methoxy‐azobenzene‐4′‐oxy)hexyl methacrylate (M), by atom transfer radical polymerization (ATRP) in the presence of CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as a catalyst system, and in chlorobenzene solvent, is reported. The degree of branching (DB), and the molecular weights and polydispersities of the resultant polymers were determined by NMR spectroscopy and size exclusion chromatography, respectively. The phase behaviors of the branched copolymers were characterized by differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). The degree of branching of the branched copolymers could be controlled by the comonomer ratio in the feed and influenced their liquid‐crystal properties. Liquid‐crystal properties were not exhibited when the comonomer ratio was low. Comonomer ratios greater than 8 gave polymers with a lower number of branches, which exhibited both a smectic and a nematic phase.

A polarized optical micrograph of the smectic phase texture of a polymer synthesized here with a higher comonomer feed ratio (magnification × 400).  相似文献   


设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号