基于偶氮液晶的PDLC膜光调制研究

采用聚苯乙烯和光敏混合向列液晶(5CB＋BMAB), 通过溶剂引发相分离制备了聚合物分散液晶膜(PDLC). 利用偶氮液晶的光致相变, 实现了聚合物分散液晶薄膜的光控开关. 实验结果表明, 在PDLC膜内部液晶微球中, 液晶分子呈双极形分布. 其光控温度区间19～36 ℃之间. 以360 nm附近紫外光照射之后, PDLC膜的最大透光率从6%增加到93%. 在相同的工作距离下, 光调制的时间与PDLC膜内部微孔直径相关. 在相同的液晶浓度下, 直径越小, 调制时间越长.     

液晶聚合物/柔性链聚合物共混体系相分离形态

利用元胞动力学方法在二维情况下对浓度、取向序参量的含时Ginzberg-Landau方程进行数值求解,研究了液晶聚合物/柔性链聚合物共混体系的相分离动力学,考察了浓度、取向有序过程的耦合对相分离形态的影响.结果表明,此耦合作用对相分离的时间进程以及相分离图样的空间排布都有影响.液晶聚合物的取向有序相当于增加了两组分间的不相容性而促进两相分离;两个序参量在热力学方面的耦合使液晶聚合物趋向于沿着界面方向取向,而动力学方面的耦合使液晶聚合物分子沿着其取向方向扩散,相分离图样的空间排布由这两种效应共同决定通过极化率张量的定义用数值方法模拟得到了相分离体系的小角光散射图样,结果表明,散射强度分布具有方位角依赖性,它是由浓度、取向序参量的空间变化共同决定的.     

侧链型丙烯酸酯共聚物相变的正电子湮没谱研究

利用正电子湮没技术对侧链型热致高分子液晶丙烯酸酯共聚物进行了变温相变研究．除实验标识出样品的相变温度点外，根据试样中自由体积随温度的变化关系，对高分子液晶材料内部立链、侧链以及介晶基元的相变行为特点进行了探讨，并就与小分子液晶变化特点的一些不同做了解释．     

聚合物分散液晶(PDLC)材料的光聚合反应

以Ar+激光器为光源, 采用虎红、 N-苯基甘氨酸、二季戊四醇羟基五丙烯酸酯和乙烯基吡咯烷酮分别作为光引发剂、共引发剂、预聚物和稀释剂, 与液晶材料TEB30A结合, 通过光聚合反应, 制备了聚合物分散液晶(PDLC), 用紫外光谱和荧光光谱对其反应机理进行了分析. 实验结果表明, PDLC是通过光引发剂吸收光子能量后与共引发剂相互作用, 形成自由基中间体并引发聚合反应, 使预聚物与液晶产生相分离形成的.     

丙烯酸酯/液晶体系的光聚合反应动力学对PDLC电光性质的影响

采用光-示差扫描量热法(P-DSC)和光-流变学(P-Rheology)技术,测定了丙烯酸酯/液晶体系的光聚合反应动力学和凝胶化时间.基于自催化模型和凝胶时间-温度关系,计算了体系的光聚合反应速率常数和活化能,探讨了单体结构与组成、反应温度对体系光聚合动力学的影响,并研究了聚合物分散液晶(PDLC)的电光响应行为与相分离结构对光聚合动力学的依赖性.结果表明,升高反应温度、增加体系的单体反应活性和平均官能度,均提高了体系的光聚合速率常数,缩短了光聚合凝胶时间.随着单体反应活性和平均官能度的提高,体系的光聚合反应活化能明显降低,且凝胶化前的光聚合反应活化能低于光聚合全过程的平均反应活化能.当液晶含量为50%时,形成的PDLC呈亚微米尺度的双连续相结构.随着光聚合反应温度的升高,光聚合速率加快,导致凝胶时间缩短、相分离程度降低,使PDLC中液晶相尺寸变小、聚合物网络致密化,PDLC的弛豫时间延长、饱和电压降低,而开启时间和阈值电压变化不大.     

液晶基元直接横挂于主链上的液晶共聚物研究

以含有液晶基元的单体，２，５－双（４－甲氧基苯甲酰氧基）苯乙烯与丙烯醇，通过自由基共聚合反应，首次合成了一系列含液晶性单体和非液晶性单体两种结构的共聚物．采用ＤＳＣ、偏光显微镜和Ｘ－衍射方法研究了共聚物的液晶行为，发现单体和所有的共聚物均有明显的热致液晶性及较宽的液晶态温度范围；随共聚物中液晶性单体含量增加，共聚物玻璃化转变温度Ｔｇ和热分解温度Ｔｄ有所上升，但Ｔｇ的变化较小．     

尼龙11在高压下的结晶研究

用ＤＳＣ、ＷＡＸＤ、ＩＲ等对在０．１ＭＰａ－０．６５ＧＰａ压力下尼龙１１（ＰＡ１１）的结晶样品进行了研究。分析了压力对ＰＡ１１结晶的影响。研究了加入１％液晶聚合物对ＰＡ１１的结晶的诱导作用。结果表明：压力有助于ＰＡ１１晶形的完善，液晶聚合物对ＰＡ１１的结晶有明显的诱导作用，使ＰＡ１１在较低的压力（０．１ＧＰａ）和较短的时间（１５ｍｉｎ）内即可得到较为完整的结晶。     

环氧树脂基高分子分散液晶材料相分离过程的研究

根据高分子分散液晶材料在相分离过程中透光率的变化,研究了高分子分散液晶材料相分离过程与液晶浓度、温度的关系,观察到相分离过程中的周期性的起伏现象．对相分离过程与高分子分散液晶材料的电光性能作了初步探讨     

聚合物稳定液晶材料研究进展

聚合物稳定液晶材料在显示传感、温度调控、智能材料等方面表现出优异性能,成为液晶材料领域的研究热点。针对向列相液晶、胆甾相液晶、铁电相液晶、蓝相液晶和其他相态液晶,分别介绍了聚合物网络在不同相态液晶中的作用,阐述了不同聚合物稳定液晶材料的特点及光学性能,综述了聚合物稳定液晶材料的研究进展,并指出了聚合物稳定液晶材料面临的机遇和挑战,旨在推进功能材料的发展及利用。     

新型侧链液晶聚甲基丙烯酸酯研究

以横向取代的液晶基元为侧基合成了聚甲基丙烯酸酯,并对此聚合物进行初步表征.在玻璃化温度(170℃)以上样品进入液晶态.样品较高的玻璃化温度以及能形成液晶态的特性被认为是棒状液晶基元使聚合物分子链刚性化的结果.     

Folded chain crystallization of random terpolymer liquid crystal polymers from the nematic state

The morphology of ca. equimolar random terpolymer liquid crystal polymers of an aliphatic segment of 4–7 carbon atoms, oxybenzoate, and dioxyphenyl crystallized from the nematic state in the form of thin films on glycerine by slow cooling and quenching has been characterized by electron microscopy (TEM) and diffraction (ED). In all cases a folded chain, lamellar structure is found. The ED studies suggest adjacent reentry, and despite a large ΔH, indicate no change in lateral molecular packing at the crystal-“liquid crystal” transition with a transformation to the nematic state at a higher temperature “liquid crystal”-liquid crystal transition. The results are interpreted as suggesting similar folded chain, lamellar morphology in the nematic state. © 1992 John Wiley & Sons, Inc.     

Thermotropic and optical behaviour of new PDLC systems based on a polysulfone matrix and a cyanoazomethine liquid crystal

The thermotropic and optical characterisations of a novel polymer dispersed liquid crystal (PDLC) system based on polysulfone UDEL P-1700 as polymer matrix and a low molecular weight liquid crystal compound containing a mesogenic azomethine core and a cyano-substituent were investigated. The PDLC samples were prepared by solvent-induced phase separation (SIPS) and thermally induced phase separation (TIPS) methods using various compositions in the two components. Information on the morphology and phase structure was obtained by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction measurements. PDLC systems with well-defined droplets were obtained for the composite with medium content of liquid crystal compound. The optical characterisation of these materials was performed by analysing their UV–visible absorption and photoluminescence emission as a function of the liquid crystal aggregation degree.     

大分子引发剂分子量对接枝聚合物基体的PDLC电光性能的影响

以可逆加成-断裂链转移(RAFT)、引发转移终止(iniferter)活性自由基聚合相结合的方法,用一步法制备了不同分子量的大分子引发剂RAFT-PS-co-PCMSI(MI),并通过紫外光聚合诱导相分离法制备了以接枝聚合物为基体的聚合物分散液晶(PDLC)膜.研究了不同分子量的MI对PDLC的微观形貌,关闭状态透光率,阈值电压,饱和电压以及记忆效应等方面的影响.研究表明,降低PDLC中MI的分子量,会使得液晶微滴粒径增大,阈值电压(Vth)、饱和电压(Vsat)减小,记忆效应、关闭状态透光率升高.     

<Superscript>2</Superscript>H-NMR investigation after a polymerisation-induced phase separation process*

Polymer-dispersed liquid crystals (PDLC) are composite materials consisting of micron-sized droplets of liquid crystal dispersed in a polymer matrix. The easiest method to obtain a PDLC film is the polymerisation-induced phase separation process (PIPS). The liquid crystal is mixed with a monomer of low molecular weight and polymerisation is induced by heat or UV light. The increasing molecular weight of the polymer causes the phase separation of liquid crystal from the polymer matrix as micron-sized droplets. In this work, we have studied the structural changes induced in the polymer matrix of a PDLC after the PIPS process by deuterium nuclear magnetic resonance. Two different selectively deuterated monomers have been synthesized and investigated: isobutyl methacrylate (IBMA-d₂) and methyl methacrylate (MMA-d₃). The main results were the disappearance of the characteristic two-site hop in poly-IBMA, due to liquid crystal molecules, and the lack of unreacted MMA molecules in the liquid crystal droplets. In this last case, we found that it is possible to confine temporarily the unreacted MMA molecules within liquid crystal droplets.Abbreviations MMA Methyl methacrylate - IBMA Isobutyl methacrylate - PDLC Polymer-dispersed liquid crystal - PIPS Polymerisation-induced phase separation - ²H-NMR Deuterium nuclear magnetic resonance*Dedicated to Professor V. Bertini for his 70^th birthday     

含Gemini表面活性剂的PVA分散液晶的微结构与性能

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.     

新型弯曲形双偶氮苯类液晶合成及光致异构性能研究

弯曲形偶氮苯液晶由于其偶氮键独特的光致可逆异构化性能,已成为光电子信息材料研究的热门课题,但光响应速度慢已成为制约其发展的关键因素.目前报道的弯曲型偶氮类液晶化合物的偶氮键都距离中心核较远的位置,光致异构的响应时间较长,大都在分钟以上,不利于光敏器件应用研究.本工作试图以2-甲基-1,3-间苯二胺为中心核,将偶氮键紧挨中心核两边,末端为直链烷基,设计合成了一系列新型弯曲形双偶氮苯类液晶化合物,以期缩短光响应时间.通过IR, 1H NMR, 13C NMR和ICP-MS光谱鉴定这些化合物的分子结构,经差示扫描量热仪(DSC)和偏光显微镜(POM)测定其液晶相变温度和相态织构;并通过测定2-甲基-1,3-双(4-((4-庚基苯基)酯基)-1-(E)-偶氮苯基)苯(2c)的紫外-可见光的吸收光谱研究其光致异构化性能,通过UV-Vis光谱仪和偏光显微镜(POM)测定其液晶化合物以及掺杂向列相液晶材料的光致异构现象和响应时间.实验结果表明,所有设计合成的弯曲形双偶氮苯类液晶化合物均具有近晶相相态,且相态温度范围较宽,当近晶相态化合物2c掺杂到向列相混合液晶中时,其光致异构响应时间为2~3 s,在日光下液晶态恢复时间为3~4s,在乙酸乙酯稀溶液中时10s可达到光稳态.说明这类弯曲形双偶氮液晶化合物具有较快的光致异构响应速度.     

Effect of electric field on phase separation of polymer dispersed liquid crystal

The kinetics of the polymerization induced phase separation of liquid crystal (LC)/monomer mixture has been investigated by means of depolarized light intensity technique and polarized light microscope (PLM). To examine the effect of the electric field, a DC electric field was applied across the mixtures during the phase separation process. The kinetic study indicates that the phase separation process is accelerated when the electric field is applied. The morphologies of the formed polymer dispersed liquid crystal (PDLC) films were observed by PLM. The electric field applied during the phase separation process yields the PDLC with small LC domains and fine morphologies. The clearing temperature (T_NI) of the formed PDLC films was measured by the PLM and it is found that the T_NI increases with the applied electric field intensity.     

The effects of some factors on the rheological properties of the lyotropic liquid crystals formed in Brij97/NaDC/IPM/water system: compositions,temperature and polyphenols

In this paper, interaction between Brij97 and NaDC in mixed micelles was studied by surface tension method. Phase behavior for Brij97/NaDC/IPM/H₂O system was investigated at the desire molar ratio of α_NaDC?=?0.42 and the human body temperature of 37?°C. Hexagonal and cubic liquid crystal were found in this system analyzed by small angle x-ray scattering (SAXS). some factors were changed to affect the rheological properties of liquid crystal. Rheological investigations showed: The higher content of water and lower experimental temperature favored the greater values of shear viscosity and viscoelastic modulus; The sample was closer to the plastic fluid and was more likely to recover from disturbed state to equilibrium state at lower ratio of NaDC; The curcumin and TP can influence the shear viscosity, viscoelastic properties and phase transition temperature, even change the structure of liquid crystal. This supplies a way to adjust rheological properties, structure and even phase transition by altering those factors.     

聚对偶氮氧苯酚酯系列热致性液晶高分子的相转变

合成含有不同亚甲基数（ｎ＝４—１２，１４）的主链型热致性液晶高分子──聚对偶氮氧苯酚二元羧酸酯．用ＤＳＣ和ＦＴＩＲ观测了相转变的奇偶效应，揭示了液晶相转变过程中分子间相互作用力性质的变化．并与聚２，２＇－二甲基对偶氮氧苯酚二元羧酸酯系列进行了比较，讨论了中介单元的对称性对液晶高聚物相转变和对液晶相稳定性的影响．