高度支化水性聚氨酯的合成及性能EI

以甲苯-2,4-二异氰酸酯(TDI)、聚碳酸酯二醇(PCDL)、二羟甲基丙酸(DMPA)和聚醚胺(ATA)为原料,采用A2+B3法合成了具有高度支化结构的水性聚氨酯(HBAPU)乳液。用红外光谱(FT-IR)对产物结构进行表征;用光子相关光谱(PCS)研究了乳液的稳定性能,NCO/OH=1.3,w(DMPA)=6%时可以得到稳定的HBAPU乳液;采用旋转黏度计、差式扫描量热仪(DSC)、热失重分析仪(TG)、电子拉力机对产物的流变行为和各种性能进行了测试。结果表明,相对于线性水性聚氨酯(LAPU),HBAPU产物具有较低的黏度、良好的热稳定性、较高的Tg和拉伸强度。     

超支化预聚物的合成及对聚合物分散液晶膜电光性能的影响

聚合物基体对聚合物分散液晶(PDLC)膜电光性能影响很大。文中,用不同比例单乙烯基和二乙烯基单体通过可逆加成-断裂链转移自由基聚合(RAFT)得到了一系列超支化聚合物。这些超支化聚合物可作为"活性"预聚物用于聚合诱导相分离(PIPS)来制备超支化树脂基PDLC膜。结果表明,添加不同预聚物导致不同的表面形貌,进而影响到阈值电压大小。驱动电压对聚合物基体分子量有一定的依赖性,分子量高的基体驱动电压相对较高。此外,滞后和记忆效应随基体支化度提高而减小,这可能与超支化结构增强了聚合物与液晶间的相互作用力有关。     

低阈值的聚合物分散液晶膜厚对其电光性能的影响

采用聚合物诱导相分离方法制备PDLC膜,主要研究了膜厚对PDLC膜电光特性的影响。结果表明,膜厚对PDLC中液晶微滴的尺寸与形状有很大影响,在一定范围内随着膜厚的增加,液晶微滴变得细小均匀,进而使液晶的阈值电压及饱和电压增加,但同时使液晶的下降时间缩短,有助于提高响应速度。     

Investigation of nonionic diazo dye-doped polymer dispersed liquid crystal film

Sudan black B (SBB) was used to investigate as the nonionic diazo dye-doped in polymer dispersed liquid crystal (PDLC) display, by polymerization-induced phase separation (PIPS) method. The maximum absorbance, contrast ratio, dichroic ratio and the order parameter of nonionic diazo dye in nemetic host (TL203) were investigated using UV?CVis polarized spectroscopy. The orientation of the dye molecules was controlled by electric field, which enabled the contrast ratio of the dye to be obtained by electrically switching. The change occurring on droplet morphologies and electro-optical properties of PDLC film with the change in contents of Sudan black dye and liquid crystals (LC) contents was investigated. We found an increase in LC droplet sizes with the increase of diazo dye and LC contents. Moreover the addition of small amount of nonionic diazo dye reduced the threshold voltage (V $_{\boldsymbol{\rm th}})$ , increased off-state transmittance, enhanced the contrast ratio and decreased the response time of dye-doped PDLC. Additionally the change in transition temperature of LC and changes in LC droplet morphologies with the addition of dye were also observed. Such changes were observed with the images taken by polarized optical microscope (POM). The detail discussions on such behaviours were also made.     

大分子链转移剂活性对聚合物分散液晶电光性能的影响

采用可逆加成-断裂链转移(RAFT)、引发转移终止(Iniferter)、反向原子转移自由基聚合(RATRP)等活性自由基聚合方法,合成了分子量相近而带有不同端基的大分子链转移剂。通过紫外光聚合诱导相分离法制备聚合物分散液晶(PDLC)膜。通过研究大分子链转移剂光引发活性,发现采用RAFT聚合制备的大分子链转移剂具有较高的光活性,带有Iniferter活性基团的大分子链转移剂光活性很低。对不同大分子链转移剂制备的PDLC膜的电光性能进行比较,发现采用RAFT法合成的具有高光活性的大分子链转移剂能够使PDLC膜具有较高的开态透光率和较低的驱动电压。加入大分子链转移剂会导致PDLC记忆效应升高。     

Electrooptical properties and microstructure of polymer-dispersed liquid crystal doped with various reinforcing materials

Different types of reinforcing material, such as hydrophilic silica (Aerosil 200), (1-propylmethacrylate)-heptaisobutyl-substituted PSS (POSS-1), octavinyl-substituted PSS (POSS-8), octamethyl-substituted PSS (POSS-octa), and poly(dimethylsiloxane) (PDMS) were incorporated into a conventional polymer-dispersed liquid crystal (PDLC) system to enhance electrooptical properties by increasing phase separation, resulting from increasing the gel content and decreasing the viscosity of the mixture. The mixtures with POSS-1, POSS-octa, and Aerosil 200 show lower viscosity than the neat mixture, caused by the weak interaction of monomer molecules because of inserting these particles into the monomer chains, whereas the mixtures with POSS-8 and PDMS show an increase in viscosity. The PDLC film with POSS-1 represents the lowest off-transmittance value because the gel content is above 94% and the droplet size of the LC is optimal. However, when the gel content is decreased, the droplet size of the LC in the film becomes large because of unreactive monomer flowing into the LC, giving rise to the increase in off-transmittance value.     

一种新型PDLC薄膜电-光性能的研究

选用丙烯酸胆固醇酯/甲基丙烯酸β-羟乙酯/液晶复合体系,在紫外光照射下制备聚合物分散液晶薄膜.研究了两种丙烯酸酯类单体的配比对聚合物分散液晶薄膜的电-光性能的影响规律,由此确定了制备综合电-光性能优异的PDLC薄膜材料的最佳制备条件.     

聚合物分散液晶的相行为

针对聚合物分散液晶(PDLC)二元体系进行了研究，主要包括外加直流电场下制备的PDLC的相图研究以及PDLC形成过程中相分离情况。在PDLC制备过程中由于外加直流电场对小分子液晶的作用，使液晶在此二元结构中的清亮点发生变化。结果表明，直流电场的引入导致PDLC中液晶清亮点升高。相分离行为主要是跟踪PDLC形成过程中由于小分子液晶与高分子链段之间的排斥作用而引起的相分离，研究了不同条件下PDLC相分离的快慢。     

Droplet orientation and optical properties of polymer dispersed liquid crystal composite films

The electro-optic and thermo-optic properties of polymer dispersed liquid crystal (PDLC) films have been investigated. The effects of applied voltage and temperature on liquid crystal droplet morphology and its transmission characteristics were studied. Threshold voltage (V_th) and optical transmission increases with increasing temperature. It may be due to the reduction in effective voltage drop across the liquid crystal droplets in the composite matrix. The liquid crystal droplet size was found to vary in the range of 5–28 μm.     

溶剂法制备聚合物分散液晶膜

用溶剂法制备了聚合物分散液晶膜。采用偏光显微镜、扫描电子显微镜和电光仪对相分离和聚合物分散液晶材料的电光性能作了初步探讨。研究结果表明，升温速度和聚合物含量对PDLC膜的相分离结构和响应电压有显著的影响。     

Pixel-isolation walls of liquid crystal display based on prepolymer containing vinyl cinnamate

Pixel-isolated liquid crystal (PILC) mode investigated in this work is obtained by phase separation induced by the anisotropic photoreaction of a prepolymer containing a vinyl cinnamate monomer. It was found that the incorporation of the cinnamate monomer was an efficient method for the control of the interfacial properties between LC and polymer walls. Polarization-selective photo-curing of the prepolymer containing a cinnamate monomer was closely related with the liquid crystal orientation at the polymer wall boundary resulting in electro-optical performance improvement.     

Gradient polymer-disposed liquid crystal single layer of large nematic droplets for modulation of laser light

The light modulating ability of gradient polymer-disposed liquid crystal (PDLC) single layer of large droplets formed by nematic E7 in UV-cured polymer NOA65 is studied. Operating at relatively low voltages, such PDLC film with a of thickness 10-25?μm and droplet size up to 50?μm exhibits a good contrast ratio and is capable of producing a large phase shift for the propagating coherent light. For a linearly polarized He-Ne laser (λ=633?nm), an electrically commanded phase shift as large as π/2 can be obtained by the large-droplet region of the film. The electrically produced phase shift and its spatial profile controlled by the thickness of the gradient PDLC single layers of large nematic droplets can be useful for tunable spatial light modulators and other devices for active control of laser light.     

以ET为柔性间隔基的嵌段热致液晶共聚酯的合成及表征

用溶液缩聚法合成了含柔性间隔基的嵌段热致液共聚酯。由于在TCE／Py溶液中共聚酯溶解度较小及溶液中副反应显著，合成的嵌段共聚酯特性粘度都小于0．30dL/g，DTA和偏光显微镜对嵌段共聚酯的液晶性和相转变研究结果表明，所有嵌段共聚酯都为向列相热致液共聚酯。     

Improvement in device performance from a mixture of a liquid crystal and photosensitive acrylic prepolymer with the photoinduced vertical alignment method

In a multicomponent nematic liquid crystal (NLC) mixture of a liquid crystal (negative-type NLC) and a photosensitive acrylic prepolymer, photopolymerization upon UV irradiation induces the separation of the LC and photosensitive acrylic prepolymer layers, thereby leading to a vertical arrangement of LC molecules. In this study, we propose a simple vertical alignment method for LC molecules, by adding a chiral smectic A (SmA∗) liquid crystal having homeotropic texture characteristics to an NLC mixture solution. Measurements of electro-optical properties revealed that the addition of the SmA∗ LC not only strengthened the anchoring force of the copolymer alignment film surface, but also significantly enhanced the contrast ratio (∼73%), response time and grayscale switching performance of the device.     

Improvement in device performance from a mixture of a liquid crystal and photosensitive acrylic prepolymer with the photoinduced vertical alignment method

Abstract

In a multicomponent nematic liquid crystal (NLC) mixture of a liquid crystal (negative-type NLC) and a photosensitive acrylic prepolymer, photopolymerization upon UV irradiation induces the separation of the LC and photosensitive acrylic prepolymer layers, thereby leading to a vertical arrangement of LC molecules. In this study, we propose a simple vertical alignment method for LC molecules, by adding a chiral smectic A (SmA?) liquid crystal having homeotropic texture characteristics to an NLC mixture solution. Measurements of electro-optical properties revealed that the addition of the SmA? LC not only strengthened the anchoring force of the copolymer alignment film surface, but also significantly enhanced the contrast ratio (～73%), response time and grayscale switching performance of the device.     

Linear size gradient single layers of polymer-dispersed liquid crystal micrometer-sized droplets for diffractive optics

An experimental study of coherent light diffraction by wedge-formed single layers composed of liquid crystal (LC) micro-sized droplets dispersed in a transparent solid polymer matrix is reported. The micrometer-sized polymer-dispersed liquid crystal (PDLC) material contains prolate-ellipsoid-like LC droplets with a linear-gradient size distribution along the wedge slope. The droplet diameter in the films reaches several tens of micrometers, defined by the wedge. Such a droplet organization in a two-dimensional layer provides both spatial and electrical control of the coherent light diffraction by the LC/polymer interface.     

Thermal behaviour of poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) tri-block copolymers

Thermal behavior of poly(-caprolactone)-poly(ethylene glycol)-poly(-caprolactone) tri-block copolymers with different block lengths is examined. Thermal behavior of specimens crystallized under the isothermal and dynamic condition are characterized by DSC. Also WAXD and SAXS are employed to investigate the structure. Depending on the relative length of each block, tri-block copolymers can be classified into three groups: PCL dominant crystallization; PEG dominant crystallization; and the competing case. When the crystallization of PEG and PCL are competing, the crystallization of each block shows strong dependency on the thermal hystory of crystallization, leading to multiple melting and crystallization peaks. Also, the typical micro-phase separation of block copolymers seems to play an important role, competing with crystallization, especially under the dynamic crystallization condition.     

Investigating of polysulfide and epoxy‐polysulfide copolymer curing

Polysulfide can be cured in various methods. In this work, the effect of various oxidative curing agents (manganese dioxide and para quinonedioxime) in presence of curing accelerator (Diphenylguanidine) on mechanical‐dynamical properties and cure time of polysulfide resin (G4) was investigated. Results showed that mentioned oxidative curing agents have no remarkable effect on mechanical properties and cure time. But preferred method is preparation of polysulfide‐epoxy copolymer. This copolymer is a new class of liquid polymer composition containing block copolymers, with alternating blocks of polysulfide and polyepoxide. in different epoxy/polysulfide ratio, the epoxy‐polysulfide copolymer showd different tensile strenght, elongation, hardness, gel time, viscosity and Tg, but epoxy free polysulfide approximately revealed constant mechanical and dynamical properties so that epoxidized polysulfide had excellent mechanical properties and suitable curring times in comparison with those samples which were cured in other methods. FT‐IR spectroscopy, viscometry and GPC were used to verify the formation of epoxy‐polysulfide copolymer. Results obtained from DMTA and SEM showed that phase separation of epoxy resin from the copolymer matrix took place and The glass transition temperature (Tg) of the cured copolymer was between the cured epoxy and polysulfide glass transition temperatures.     

聚合物结构对聚合物网络稳定液晶薄膜电光性能的影响

用带有联苯结构的双丙烯酸酯和单丙烯酸酯作为单体,采用紫外光引发聚合诱导相分离法制备了聚合物网络稳定液晶(PSLC)薄膜。研究了不同液晶含量、固化时间、单体结构、取向层对PSLC膜电光性能的影响。结果表明,随着液晶含量的增加,样品的关态透光率(TOFF)随之增大,驱动电压则呈减小趋势;相对而言,随固化时间的增加,样品的TOFF则降低。在PI作取向层时,由双丙烯酸酯单体制备的样品表现出了较高的TOFF,而由单丙烯酸酯单体制得的样品,因其聚合物网络结构的不稳定性,在较低电压情况下就出现了"变形"的电光曲线。     

Effects of rigid structures containing (meth)acrylate monomers and crosslinking agents with different chain length on the morphology and electro-optical properties of polymer-dispersed liquid crystal films

ABSTRACT

This contribution investigates the preparation of polymer-dispersed liquid crystal (PDLC) films based on meth(acrylate) monomers containing rigid structures. The current study specifically focuses on comparison of the monomers on the basis of meth(acrylate) side group, flexible/rigid structures and rigidity. We find that methacrylate monomers exhibit more preferable electro-optic properties than that of the acrylate monomers. Furthermore, through the systematic variation of rigidity, composition of the monomers and chain length of crosslinking agents, both the morphologies and electro-optic properties of these films are found to be adjustable. A composite film is demonstrated by employing moderately rigid monomer (tetrahydrofurfuryl methacrylate) with low driving voltage (21.0?V) and high contrast ratio (87.5). Therefore, the studies here provide a new approach to optimize the electro-optical properties of the PDLC films by introducing monomers with rigid structures.