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《应用化学》2021,(10)
正19世纪80年代后期,奥地利植物学家Reinitzer和德国物理学家Lehmann共同发现了液晶,创立了液晶科学。20世纪70年代,液晶显示技术实现了革命性突破,风靡全球。液晶高分子的研究始于1937年的生物高分子液晶,随即受到广泛关注,尤其是杜邦公司基于溶致液晶芳香族聚酰胺的液晶纺丝技术在1972年推出的Kevlar系列高性能纤维产品,极大地推动了液晶高分子的飞速发展。近几十年来,基于热致液晶芳香族聚酯的高性能工程塑料如雨后春笋般不断涌现,高性能液晶高分子结构材料也成为全球研究热点。同时,侧链高分子液晶、聚合物分散液晶、聚合物稳定液晶、全息聚合物分散液晶以及新型结构的高分子液晶、超分子液晶在显示、传感、防伪、数据存储和电子封装等领域的应用也成为高性能液晶高分子功能材料的研究亮点。其中让我们倍感骄傲的是,我国科学家周其凤院士于1987年设计、合成了甲壳型液晶高分子,为液晶高分子科学与材料的发展做出了原创性贡献。当前,液晶材料的高分子化、高分子材料的液晶化已成为化学、材料、光学工程和信息工程等相关学科的重要研究方向,尤其近期在光存储、5G通讯领域中的应用备受关注。 相似文献
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从分子场理论出发,推导出了spinodal方程和浓度效应引起的各向同性-各向异性转变方程.计算结果表明,在柔性高分子/小分子液晶的相图上除了具有经典的各向同性spinodal线以外,还存在鲜为报道的各向异性spinodal线,这两种不同的spinodal线通过各向同性-各向异性转变线连接在一起.在柔性高分子/小分子液晶的相图的不同区域中将会发生不同的相分离机理.这一体系的相平衡线不一定与spinodal线会聚于临界点.这些结果有助于我们深入了解高分子/液晶体系与一般高分子/溶剂或高分子/高分子体系不同的特殊性质,从而达到控制材料的结构与性能的目的. 相似文献
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柔性高分子/小分子液晶混合物的自洽场理论 总被引:5,自引:1,他引:5
发展了柔性高分子/小分子液晶混合物连续自洽场理论,将小分子液晶模型化 为取向与位置无关的单体分子,小分子液晶间存在各向异性的Maier-Saupe相互作 用,该理论可还原成高分子和各向同性小分子组成的Flory-Huggins溶液理论和纯 液晶的Maier-Squpe液晶理论,通过数值解自洽场方程组,还将理论用于研究柔性 高分子/小分子液晶混合物相分离开界面性质,得到的结果与用Helfand格子界面理 论和MOnte Carlo模拟的结果一致。 相似文献
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全息聚合物分散液晶(HPDLCs)是由富聚合物相与富液晶相周期性排列而成的结构有序高分子复合材料.HPDLCs通过单体/液晶复合体系的光聚合诱导相分离而形成,如何调控并定量化描述复合体系的光聚合反应动力学、凝胶化行为和相分离程度,进而获得结构规整、电光性能优异的HPDLCs是关键难题.专论概述了光引发体系、单体结构、纳米无机材料掺杂对HPDLCs结构及性能的影响.光引发阻聚剂通过引发和阻聚的竞争与协同,降低了光聚合反应速率、延迟了凝胶时间,促进形成衍射效率达90%的HPDLCs.超支化单体降低了复合体系黏度和光聚合反应速率,延迟了凝胶时间,促使形成衍射效率达94%、具有一维光子晶体结构的HPDLCs.丙烯酰胺单体优化了相分离结构,将HPDLCs的衍射效率提升至98%.纳米硫化锌掺杂在保持规整结构和高衍射效率的同时,大幅降低了HPDLCs的驱动电压.研究还确定了HPDLCs的相分离程度与凝胶时间的函数关系.构建兼具高衍射效率与低驱动电压的HPDLCs,推进其在彩色3D图像存储等领域的应用仍是重要课题. 相似文献
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采用N,N'-二(十二烷基)-N,N,N',N',N″-五甲基-1,4,7-三氮杂双碘化氨为Gemini表面活性剂,液晶为4-正戊基-4'-氰基联苯(5CB),通过微胶囊法制备了聚乙烯醇(PVA)分散液晶薄膜,着重研究Gemini表面活性剂对PVA分散液晶薄膜的微结构、电光特性的影响.结果表明,加入Gemini表面活性剂仅略微增加了PVA与5CB液晶的相容性,PVA分散液晶仍保持较高的相分离程度,但是Gemini表面活性剂使液晶微滴尺寸明显变小,液晶相均匀分散地于PVA基体中,液晶指向矢构型由两极型变化为径向型,PVA分散液晶薄膜的对比度和响应速度明显提高,同时保持较低的驱动电压. 相似文献
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The thermal annealing process was proposed to purify the pixel regions of a liquid crystal (LC) cell with polymer walls. This technique, based on thermal‐induced phase separation, successfully evicts the residual monomers from the LC volume and significantly improves electro‐optical properties of the polymer‐wall LC devices. The influence of the annealing process on the purity of LC‐rich domain and the electro‐optic properties of a LC cell was explored with a series of experiments. According to the experimental results, the annealing technique is extremely prospective for constructing flexible polymer‐wall LC display applications. 相似文献
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Reaction-induced phase separation in rubber-modified epoxy resin 总被引:1,自引:0,他引:1
The phase separation mechanism,and structure development during curing of epoxy with a novel liquid rubber-ZR were investigated by time-resolved light scattering,optical microscope and differential scanning calonmetry (DSC) The mixture loaded with curing agent was a single-phase system in the early stage of curing.When the cure reaction proceeded,phase separation took place via the spinodal decomposition induced by polymerization of epoxy resin.This was supported by the characteristic change of light scattering profile with curing time.Cure reaction plays an important role in the progress of phase separation.The bigger the cure reaction rate is,the longer periodic distance will be.The overall two-phase structure was basically locked in when the conversion approached 80% estimated by DSC,and finally the co-continuous two-phase structure was successfully obtained. 相似文献
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Fatima Zohra Abdoune Leila Benkhaled Lahcène Méchernène Ulrich Maschke 《Macromolecular Symposia》2011,303(1):100-107
Summary: The time relaxation of the optical transmission of polymer-dispersed liquid crystal films was investigated after application of an electric rectangular pulse. These films, consisting of liquid crystalline microdomains dispersed in a polymer matrix, were obtained by polymerization induced phase separation using ultraviolet and electron beam curing techniques. The effects of the curing procedure and film thickness on the transmission properties were investigated. The electro-optical response was expressed via a hierarchy of order parameters. A good agreement between the experimental data and calculated transmission values was found. 相似文献
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D. L. Rodin A. N. Varnavski S. Yu. Stefanovich M. Yu. Yablokova 《Moscow University Chemistry Bulletin》2017,72(4):161-166
In the process of curing under thermostatic conditions, the time dependence of active and reactive components of the dielectric permittivity of epoxy amine compositions that contain a thermoplastic substance is studied in a wide range of electrical frequencies. The times of gelation and vitrification are calculated from the dielectric data and the onset of the phase separation is identified. The curing behavior established by dielectric spectroscopy is confirmed by viscometry and optical microscopy. During the phase separation, the morphology of the precipitating phase differs between samples depending on the chemical nature of the curing agent. 相似文献
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The polymerization-induced phase-separation process of polyethersulfone (PES)-modified epoxy systems was monitored in situ continuously on a single sample throughout the entire curing process by using optical microscopes, time-resolved light scattering (TRLS), scanning electronic microscopes (SEM), and a rheometry instrument. At specific PES content a viscoelastic transformation process of phase inversion morphology to bicontinuous was found with an optical microscope. The rheological behavior during phase separation corresponds well with the morphology development. Light-scattering results monitoring the phase-separation process of systems with final phase inversion morphology show a typical exponential decay procedure of scattering vector qm. The characteristic relaxation time of phase separation can be described well by the WLF equation. 相似文献
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新型光活性串型液晶共聚物合成与表征 总被引:1,自引:0,他引:1
以对苯二甲酰氯,2 ,5 二[4 ((S) 2 甲基丁氧基) 苯甲酰氧基] 对苯二酚和己二醇为单体,采用溶液共缩聚的方法,合成了一系列新的光活性串型液晶共聚物.共聚物通过GPC、DSC、TG、WAXD、偏光显微镜和旋光仪等方法表征.发现所有的共聚物加热至各自的熔点以上都能形成液晶态,在液晶态可以观察到沙地织构或破碎焦锥织构.通过变温X 射线衍射证明它们为手性近晶C(S*C) 相.所有共聚物的熔点( Tm) 和液晶态清亮点( Ti) 随共聚物中己二醇用量的改变呈规律性变化.共聚物有很高的旋光性,在合成反应中旋光性保持. 相似文献
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We report on the structures and electro‐optical properties of epoxy/acrylic polymer‐dispersed liquid‐crystal (PDLC) films. A thermal stimulated current (TSC) analysis was used to investigate the physical structures of PDLC. In the TSC spectrum of PDLC, three relaxation peaks were observed: the glass transition of the liquid crystal, the glass transition of the polymer matrix, and the ρ transition. The ρ transition represents the discharge behavior of space charges, and its intensity increased as the curing time and content of the curing agent dicyandiamide (DICY) increased. The pre‐UV‐cured films with different DICY contents were thermally cured at 130 °C for various periods. The electro‐optical properties of PDLC, such as the contrast ratio and switching voltage, increased as the curing time of DICY, the content of DICY, or both increased. As the ambient temperature increased from 10 to 40 °C, the contrast ratio and switching voltage of PDLC gradually decreased. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 507–514, 2001 相似文献
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混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响 总被引:19,自引:0,他引:19
采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能 相似文献
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多官能度炔烃与叠氮化物的固化研究 总被引:6,自引:2,他引:4
采用差热扫描量热仪 (DSC)研究了不同分子量的端叠氮基聚乙二醇 (ATPEG)与N ,N ,N′,N′ 四炔丙基乙二胺及 1 ,1 ,1 三 (炔丙氧甲基 )丙烷的固化反应动力学 ,并利用FT IR跟踪了固化反应过程中特征基团的变化 .结果表明 ,ATPEG与N ,N ,N′,N′ 四炔丙基乙二胺固化反应的峰温及反应活化能均高于与 1 ,1 ,1 三 (炔丙氧甲基 )丙烷的固化反应 .增加ATPEG的分子量 ,升高了与多官能度炔烃的固化峰温 ,却降低了固化反应的活化能 .而采用扩链剂仅降低固化反应活化能 . 相似文献