响应型液晶材料研究

响应型液晶材料是指既具有液晶特性又能对外场的刺激做出相应尺寸变化的一类材料.目前,光机械效应液晶材料是响应型液晶材料研究的重点.文章对单层、聚合物以及液晶弹性体这三类主要的响应型材料体系进行了介绍和分析,探讨了它们对外界光刺激的尺寸响应及其致动机理,并对响应型材料的应用前景进行了展望.     

聚合物稳定双频蓝相液晶的亚微秒电光响应

蓝相液晶由于其出色的电光性质在信息显示和光电子领域受到了广泛的关注，然而日益发展的信息技术对信息的传递、处理、存储速度提出了更高的要求。为了进一步强化蓝相液晶的快速电光响应优势，本文以双频向列相液晶为主体，掺杂聚合单体、手性剂、光引发剂等材料制备了聚合物稳定双频蓝相液晶，通过调节双段电压脉冲时长，实现了聚合物稳定双频蓝相液晶的快速电光调控，其电光调控的开关时间均小于500 ns。     

切变聚合物网络液晶光阀

针对向列型液晶光阀响应速度慢的问题,提出了一种工作在可见光波段的切变聚合物网络液晶光阀(SLCLV).通过测定其电光响应,这种切变聚合物网络液晶(SLC)的响应时间可达几个毫秒,比相同条件下的向列型液晶的响应速度提高了一个数量级,而且对厚度依赖性小.通过理论分析,提出了SLC的工作原理,介绍了工作在可见光波段的反射式电寻址SLCLV的制作过程.器件的制作工艺简单,可靠性高.在可见光-可见光图像转换系统中,测得这种液晶光阀的帧频可达500 Hz,分辨率为81p/mm.如果能进一步提高制作工艺,这种液晶光阀在高速光学信息处理方面有广阔的应用前景.     

基于二色性染料及聚合物取向的液晶光开关的制备及其性能研究

为获得一种开关效应强、响应快且结构简单的光开关,对一种基于二色性染料及聚合物取向的液晶光开关进行研究。通过在垂直配向的液晶中加入二色性染料及聚合物,并在施加偏压的情况下照射紫外光使其发生聚合物取向效应,制得了一种具有电控偏光特性的液晶盒,进而将这种液晶盒按照偏光角度为0°/90°的方式组合为液晶光开关。对所制得液晶光开关的插入损耗、消光比和响应特性进行测试,结果表明,所制得的液晶光开关的插入损耗小于0.6dB、消光比超过13dB,具有较明显的开关效应,聚合物取向的方法则可以消除这种液晶光开关的迟滞现象,使其开关时间降低到20ms以内;通过聚合物取向过程所施加偏压的控制,二选一地,可以进一步减少其插入损耗或开关时间。     

聚合物分散型液晶薄膜中折射率匹配的优化

分析了聚俣物分散型液晶薄膜在亮态时造成折射率不匹配的各种因素，介绍了一种定量计算聚合物基体和液晶之间折射率不匹配程度的方法。最后，通过选择合适的预聚物材料和液晶材料并控制固化速率，制备出一种在开态具有较高光透过率的ＰＣＬＣ薄膜，其聚合物基体的折射率和液晶的寻常折射率，在开态时达到了较好的匹配。     

聚合物分散液晶的应用

聚合物分散液晶是液晶分子以微滴的形式分散于高分子聚合物中,所形成的性能优异的一种液晶薄膜材料。文中介绍了PDLC的3大应用领域,在大屏弯曲显示方面具有传统液晶显示技术无可比拟的优势,是制作智能玻璃的核心材料,且可用于研制性能更好的可变光衰减器、波带片、透镜和调制器等重要光学器件,并指出纳米掺杂是改进PDLC性能的研究方向。聚合物分散液晶具有广阔的应用前景,且其生产工艺简单、成本低廉,应引起国内学者足够的重视,避免未来国外形成技术垄断。     

光驱动液晶聚合物振动器研究进展

光响应液晶聚合物在光化学(如偶氮苯)或者光热(如氧化石墨烯)作用下发生有序-无序转变,进而产生宏观形变,是一类被广泛研究的智能材料。目前光驱动液晶聚合物振动器的实现主要有两种途径：一是紫外或者可见光连续照射时,偶氮苯液晶聚合物的力学特性发生非线性变化,驱动器呈现无规振动;二是通过构筑非平衡系统,利用驱动器运动过程中的自遮挡效应,在光源连续照射下自发地产生周期性、连续性运动,可用于光学信号调制、移动机器人、能量转换、轧机、马达等。本文综述了光驱动液晶聚合物振动器领域的研究进展,详细介绍了其设计原理、运动机理以及应用领域,对未来的发展趋势做出了展望。     

聚硅氧烷侧链液晶聚合物的研究进展

聚硅氧烷侧链液晶聚合物(Polysiloxane side-chain liquid crystalline polymers, PSLCPs)是一种将液晶单体、特殊功能基团等通过交联反应接枝到硅氧烷主链上形成的液晶聚合物。凭借硅氧烷主链的软性和柔性及功能基团的光热电等响应特性,硅氧烷侧链液晶聚合物在光信息储存、非线性光学、图像显示、色谱、电流变等领域具有很重要的应用价值。本文对硅氧烷侧链液晶聚合物在宽波反射、柔性光响应器件、柔性应力响应器件、电响应器件和柔性涂料等领域取得的研究进展进行了总结,并对硅氧烷侧链液晶聚合物未来需解决的问题及发展趋势做了一定的展望。     

一种光学状态可由电场控制的液晶复合材料的制备与表征

液晶材料对电、热、磁、光等外界物理量的变化具有不同的响应特性,向其中添加具有一定特性的化合物,可以得到具备一定响应特性的液晶复合材料。利用所制备的液晶复合材料对于电场变化具有响应特性的特点,制备出具有信息记录功能的复合材料。合成手性离子液体,按一定配比将其加入手征向列相液晶(N~*-LC)中,得到反射波段可电控的手征向列相液晶/手性离子液体复合材料。实验结果表明:材料初始状态为光透射状态;对材料施加直流电压40V时,样品表现为光散射状态,透过率低于10%;施加高频交流电压40V时,样品表现为半透明镜面反射,反射范围覆盖400～750nm,透射率为45%左右;撤去电场后,可恢复至初始状态,并且每种状态都具有一定的记忆效应。该种液晶复合材料制备简单,无需紫外辐射工艺,且具有电场响应特性,可以通过电场控制在可见光范围内表现出光透射、强烈光散射、半透明镜面反射3种不同状态,具有记忆效应,操作简单方便。     

一种用于液晶分子取向排列的紫外光聚合物PV4研究

研究了紫外光聚合物材料ＰＶ４的化学性质;采用偏光显微照相技术,研究厂这种材料膜对液晶ＬＣ－６７１０Ａ的取向能力;用原子力显微镜（ＡＦＭ）,研究了光聚合前后聚合物取向膜微观形貌的变化;测最了这种材料引起的液晶预倾角、单面光控取向层扭曲向列液晶显示器件（ＴＮ－ＬＣＤ）的电光特性和时间响应特性;分析了液晶分子取向排列的机理。     

Liquid‐Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase‐Separated Structures

In this report, a novel type of photoresponsive liquid crystalline polymer with a block mesogenic side‐group is demonstrated. The block mesogene is an amphipathic molecule containing a hydrophobic mesogene (azotolane moiety) and hydrophilic oligooxyethylene moieties in the same unit. The block mesogene in the polymer plays a role in liquid crystalline, amphiphilic and photoresponsive properties. As expected, a film prepared from the polymer exhibits phase separation of a lamellar structure due to cooperative motion between liquid crystal assembly and nanophase separation. The morphology of the lamellae can be aligned upon irradiation of linearly polarized light. Moreover, a photochemical phase transition induced by unpolarized UV irradiation erases the surface morphology. The erased nanostructure can be recovered by annealing or irradiation of linearly polarized light, meaning that the surface morphology is rewritable via a photochemical process.     

Nanowrinkled and Nanoporous Polyethylene Membranes Via Entanglement Arrangement Control

Crystalline homopolymers, including polyethylene (PE), which has the simplest architecture, form a nanometer‐sized combination of crystalline and amorphous components, but their arrangement control, similar to self‐assembled phase‐separation of block‐copolymers, is usually difficult. However, molecular entanglements trapped between crystalline and amorphous components of homopolymers coincide with the segmental linking points on the interfaces of the microphase separation for block copolymers. Nanowrinkled PE membranes are prepared with a network of 30 nm‐thick homogeneous lamellae using a novel entanglement control technique composed of biaxial melt‐drawing and melt‐shrinking procedures, which are limited for highly entangled ultrahigh molecular weight materials. Such a network arrangement of nanowrinkling lamellae spreading on membrane surface and also across the membrane thickness improves the mechanical properties of both tensile strength and tearing strength. Subsequent cold‐drawing causes delamination of the lamellar interfaces, leading to the resultant nanoporous morphology composed of passing‐through channels that are several tens of nanometers in diameter, without any solvent processing.     

Self‐Assembled Shape‐Memory Fibers of Triblock Liquid‐Crystal Polymers

New thermoplastic liquid‐crystalline elastomers have been synthesized using the telechelic principle of microphase separation in triblock copolymers. The large central block is made of a main‐chain nematic polymer renowned for its large spontaneous elongation along the nematic director. The effective crosslinking is established by small terminal blocks formed of terphenyl moieties, which phase separate into semicrystalline micelles acting as multifunctional junction points of the network. The resulting transient network retains the director alignment and shows a significant shape‐memory effect, characteristic and exceeding that of covalently bonded nematic elastomers. Its plasticity at temperatures above the nematic–isotropic transition allows drawing thin well‐aligned fibers from the melt. The fibers have been characterized and their thermal actuator behavior—reversible contraction of heating and elongation on cooling—has been investigated.     

Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent Vapor Annealing Using Mixtures of Selective Solvents

Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, solvent vapor annealing in supported thin films of poly(2‐hydroxyethyl methacrylate)‐block‐poly(methyl methacrylate) [PHEMA‐b‐PMMA] by means of grazing incidence small angle X‐ray scattering (GISAXS) is investigated. A spin‐coated thin film of a lamellar block copolymer is solvent vapor annealed to induce microphase separation and improve the long‐range order of the self‐assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents, which are chosen to be preferential for each block, enables selective formation of ordered lamellae, gyroid, hexagonal, or spherical morphologies from a single‐block copolymer with a fixed volume fraction. The selected microstructure is then kinetically trapped in the dry film by rapid drying. This paper describes what is thought to be the first reported case where in situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram.     

Nanostructured semiconductor block copolymers: π–π Stacking,optical and electrochemical properties

The structural and optical properties of semiconductor block copolymers containing triphenylamine as hole transport material and perylene bisimide as dye and electron transport material are reported. The polymers were prepared by nitroxide mediated controlled radical polymerisation and characterized with GPC, DSC, and TGA. The electrochemical properties as determined by cyclic voltammetry show the HOMO and LUMO values of the block copolymers to be −5.23 eV and −3.65 eV, respectively. The perylene bisimide units aggregate by π–π stacking which could be analyzed with wide-angle X-ray scattering. The absorption and fluorescence properties of the perylene bisimide polymers and monomers in solution and film were investigated. It could be shown that they are strongly influenced by intramolecular coupling between different perylene bisimide units in polymers. The block copolymers exhibit a microphase separation on a nanometer scale with a constant perylene bisimide domain width of 13 nm and lengths of up to several micrometers.     

新型二元胆甾相液晶的超分子自组装比较研究

在21世纪,液晶具有良好的动力学性质,将成为非常重要的功能性材料。它对各种刺激和环境较为敏感,因此新型液晶材料有待开发。本文以胆甾醇和丁二酸酐为原料合成了丁二酸单胆甾醇酯(AC),研究探讨了AC自组装液晶特性;AC与4,4′联吡啶通过氢键自组装形成丁二酸单胆甾醇酯与4,4′联吡啶的复合物(ACBP);AC与对胺基联苯反应得到了丁酸4,4′-([1,1'-苯基]-4,4′亚胺)-双-[4-氧-双胆甾醇酯](CBC),并进一步利用FTIR和ESI质谱等方法表征了自组装体的形成,利用DSC和偏光显微镜探讨了它们的液晶性质。展示了如何组装成超分子液晶。说明液晶分子的组装方式与胆甾相液晶的形成没有直接关系,而组装后的分子形状是其形成有序排列的决定因素。讨论了胆甾醇衍生物氢键液晶和共价液晶的不同性质,因而它们可以作为潜在的光学材料应用于实际生活中。     

Photodriven,Flexural–Torsional Oscillation of Glassy Azobenzene Liquid Crystal Polymer Networks

Cantilevers composed of glassy, photoresponsive liquid crystalline polymer networks (LCNs) are shown to oscillate at high frequency (～50 Hz) and large amplitude when exposed to light from a 442 nm coherent wave (CW) laser. Added dimensionality to previously reported in‐plane oscillations is enabled by adjusting the orientation of the nematic director to the long axis of the cantilever yielding in‐plane bending accompanied by out‐of‐plane twisting (flexural–torsional oscillation). The fundamental photoresponse of this class of glassy azobenzene liquid crystal polymer networks (azo‐LCN) is further probed by examining the influence of cantilever aspect ratio, laser intensity, and temperature. The frequency of photodirected oscillations is strongly correlated to the length of the cantilever while the amplitude and threshold laser intensity for oscillation is strongly correlated to temperature.     

含胆甾烯基结构的手性二介晶结构液晶化合物

二介晶结构液晶化合物是指分子中含有由柔性的间隔基连接2个同样的介晶结构单元（对称）或不同的介晶结构单元（不对称）的化合物。对称的二介晶结构化合物可作为高分子液晶研究的理想模型，而不对称的二介晶结构化合物，尤其是含胆甾烯基结构的二介晶结构液晶化合物由于胆甾烯基的手性呈现新型而独特的液晶相，并且其液晶行为随着连接2个介晶结构单元的间隔基的碳链长度和碳原子数的奇偶以及第二个液晶结构单元的种类有规律性的变化，引起了各国学者的关注。本文总结了含胆甾烯基结构的手性二介晶结构液晶化合物的液晶性质。     

用液晶透镜改进的望远镜腔激光器性能分析

借助于普通望远镜腔激光器的结构及其性能,利用液晶透镜的调焦、选模特性,提出了构造液晶望远镜腔激光器的设想,并从理论上验证了其存在的可能性,最后分析了该类型激光器的显著优点。     

含氟二苯乙炔类蓝相液晶的研究进展

蓝相液晶具有高度流动的自聚集的三维立方缺陷结构,在高度手性的液晶中,它们存在于狭窄的温度区间。分子中引入适当的手性中心可以制得蓝相液晶。由于氟原子的特殊性,在液晶核分子中引入含氟二苯乙炔,可以得到黏度低、双折射率及清亮点高的液晶材料。文中介绍了6类含手性端基的含氟液晶化合物(其中有一个化合物不含氟原子)。通过偏光显微镜和DSC对其相变行为进行了研究。结果表明:共有13个化合物显示蓝相;化合物结构中手性中心的细微差别都会导致蓝相的出现或消失。