Formation of anisotropic diffraction gratings in a polymer-dispersed liquid crystal by polarization modulation using a spatial light modulator

Anisotropic diffraction gratings based on a holographic polymer-dispersed liquid crystal (HPDLC) are realized by interferometric exposure using a spatial light modulator (SLM). The SLM is used in the HPDLC grating formation for anisotropic holographic recordings of two-dimensional polarization states for an incident light beam. The diffraction efficiency for P-polarization and the distinctive ratio of diffraction efficiency in P-polarization to that in S-polarization increases with the signal level applied to the SLM. The resulting volume gratings exhibit diffraction efficiency of more than 60% and a distinctive ratio of diffraction over 100. The microscopic origin of the anisotropic property is investigated by an optical polarizing microscope. The novel characteristics of the anisotropic diffraction properties of HPDLC are applied to an image reconstruction technique.     

Optical reconfiguration by anisotropic diffraction in holographic polymer-dispersed liquid crystal memory

Holographic polymer dispersed liquid crystal (HPDLC) memory is fabricated by a photoinduced phase separation comprised of polymer and liquid crystal (LC) phases using laser light interference exposures. The anisotropic diffraction induced by the alignment of LC in the periodic structure of the HPDLC memory is applied to reconstruct the configuration contexts for the optically reconfigurable gate arrays. Optical reconfiguration for various circuits under parallel programmability is implemented by switching the polarization state of incident light on the HPDLC memory using a spatial light modulator.     

Holographic grating formation in PVB doped polymer dispersed liquid crystal based on PUA

Different contents of poly(vinyl butyral) (PVB) have been incorporated into the conventional holographic polymer dispersed liquid crystal (HPDLC) composition based on liquid crystal mixture and polyurethane acrylate (PUA) with a particular composition. As the PVB content is increased, the hardness, elastic modulus and thermal stability of polymer matrix are improved because of the entanglement by PVB, which has a relatively high molecular weight compared with PUA oligomer. Diffraction efficiency is enhanced with the addition of PVB except for HPDLC film with 10 wt.% PVB owing to augmentation of the phase separation between polymer and LC, caused by the increase of elasticity of the polymer matrix. However, the increase in viscosity on adding PVB produces a slow saturation time and coalescence of the LC droplet, showing a lower diffraction efficiency at the PVB content of 10 wt.% than at 0 wt.%.     

Holographic polymer-dispersed liquid crystal memory for optically reconfigurable gate array using subwavelength grating mask

Holographic polymer-dispersed liquid crystal (HPDLC) memory formed by a subwavelength grating (SWG) mask is presented for new optical information processing. The SWG structure in a photomask is formed on the SiO(2) plate using the anisotropic reactive ion etching technique. The configuration contexts for optically reconfigurable gate arrays (ORGAs) are stored in the HPDLC memory by polarization modulation property based on the form birefringence of the SWG plate. The configuration context pattern in the HPDLC memory is reconstructed to write it for the ORGAs under parallel programmability.     

硅藻基As(Ⅴ)表面印迹材料的制备与表征

采用硅藻作为材料载体、选取硅烷偶联剂氨基丙基三甲氧基硅烷(APS)作为功能单体、As(Ⅴ)为模板离子、环氧氯丙烷(ECH)为交联剂,通过冷凝回流法制备了以天然矿物材料为载体的印迹复合材料。经扫描电镜、X射线粉末衍射、傅里叶变换红外光谱及透射电镜的表征结果表明:功能单体APS经接枝作用成功搭接在了硅藻表面,与ECH交联后形成了稳定的印迹孔穴。硅藻的孔穴及周围有明显接枝物产生,且孔穴的内部规则性更加明显。选择性实验得到了不同二元体系下As(Ⅴ)印迹复合材料的选择性系数,并根据实验数据对As(Ⅴ)的选择能力与利用前景进行了总结和评价。     

碳纤维表面等离子接枝及对碳纤维/PAA复合材料ILSS的影响

将碳纤维预浸芳基乙炔后进行空气等离子处理,使芳基乙炔接枝在碳纤维上,并用扫描电镜、红外光谱、紫外光谱、X射线衍射、拉曼光谱等多种方法进行研究。结果表明经过等离子处理以后的碳纤维/芳基乙炔复合材料的层间剪切强度(ILSS)最大可提高12.4%,而碳布接枝了PAA单体以后,可使复合材料的层间剪切强度最大提高到51.27%。      

Stabilization of volume gratings recorded in polyvinyl alcohol-acrylamide photopolymers with diffraction efficiencies higher than 90%

Abstract

Obtaining holographic volume gratings with high diffraction efficiencies that can be used under white light has been a serious problem for the polyvinyl alcohol-acrylamide-based photopolymers developed by other researchers. In this paper we propose to eliminate the residual monomer in order to stabilize the holographic gratings. The residual dye and residual monomer are the main problems in achieving high diffraction efficiencies stable under white light. In order to polymerize the residual monomer we illuminate the gratings with coherent green light and incoherent white light and we heat the grating at 80°C for different times. We also study the conservation of gratings dried in critical conditions of humidity and temperature. After stabilization the diffraction efficiencies achieved were clearly higher than 90%.     

Structure,optical and thermal decomposition characters of LDPE graft copolymers synthesized by gamma irradiation

Methyl methacrylate (MMA) monomer was grafted onto low density polyethylene by the direct method of radiation grafting. The effect of cohesive energy density of different organic solvents on the degree of grafting was investigated. It was found that the extent of grafting depends largely on the kind of solvent, in which the highest degree of grafting was achieved in the presence of dioxane, whereas the lowest degree of grafting occurred in the presence of methanol. This behaviour was attributed to the solubility parameters of the solvent, monomer and polymer. The change in structure of the LDPE graft copolymer films was characterized by scanning electron microscopy, X-ray diffraction, UV/vis absorption and thermogravimetric analysis. The X-ray diffraction results showed a decrease in the crystallinity of LDPE graft copolymer matrix at high degree of grafting. Studies were made on the UV-absorption edge, and indirect allowed transitions with their optical energy gaps are determined. At the same time the Urbach energy was evaluated. The activation energy of the thermal decomposition was calculated according to Horowitz and Metzger method.     

Preparation and characterization of novel nanocomposites based on polyacrylonitrile/kaolinite

A novel intercalation nanocomposite based on polyacrylonitrile (PAN)/kaolinite was prepared by a simple in situ emulsion polymerization in the presence of organically modified layered silicates (kaolinite). The crude kaolinite (K₀) was firstly modified by dimethylsulfoxide-methanol and potassium acetate-aqueous systems; acrylonitrile monomer was then intercalated into kaolinite by displacing potassium acetate from KAc-kaolinite (the kaolinite modified by KAc, marked as K₂). The polymer/kaolinite composites were prepared by in situ emulsion polymerization, and characterized by means of X-ray diffraction, scanning electron microscope, transmission electron microscope and thermal gravimetric analysis. Experimental results indicate that the clay layers of kaolinite in PAN/K₂ composites are well distributed and delaminated. The weight-average molecular weights were measured by small-angle X-ray scattering for all samples. The presence of clay results in an increase in molecular weights compared to pure PAN polymer due to the highly crosslinked structure.     

一种以硅为中心的星型液晶的制备与相行为研究

通过液晶基元与SiCl4 直接反应获得一种以硅为中心的星型液晶化合物,产品经柱色谱提纯,并利用红外光谱( IR)、核磁共振(1HNMR)和元素分析(EA)对其进行了结构表征,又利用偏光显微镜(POM)、差式扫描量热( DSC)和广角 X 射线衍射(WAXD)对其液晶相行为进行了研究,确定了其相态及区间为K127N144I142N116K,发现星型液晶的相态取决于液晶基元,也是向列相,其熔点和清亮点均高于液晶基元,同时星型液晶的液晶区间比其液晶基元的区间要宽,表明星型液晶具有优良的液晶性,具有潜在应用价值。     

Lattice dynamics of colloidal crystals during photopolymerization of acrylic monomer matrix

The photoinitiated bulk polymerization process, which has been used recently in the manufacture of solid optical diffraction filters, is examined to understand the dynamics of both the crystalline colloidal arrays (CCA) and the host monomer species. Our analysis indicates that volume shrinkage of the monomer, changes in the dielectric properties of the monomer, and inhomogeneities of polymerization reaction rate across the dispersion during the polymerization process, are the major contributors for observed lattice compression and lattice disorder of the CCA of silica spheres in polymerized acrylic/methacrylic ester films. The effect of orientation of photocell with respect to the radiation source on Bragg diffraction of CCA indicated the presence of convective stirring in the thin fluid system during the photopolymerization that deleteriously affects the periodic array structures. To devise reproducible and more efficient optical filters, experimental methods to minimize or eliminate convective instabilities in monomeric dispersions during polymerization are suggested. © 1998 Chapman & Hall     

竹纤维与丙烯酸的共辐照接枝改性

研究了60Co-γ射线辐照对竹纤维和丙烯酸进行接枝共聚反应条件,探讨了单体含量、辐照剂量、pH值等因素对接枝率的影响。研究结果发现,最佳共辐照接枝条件为:单体质量分数40%,辐照剂量5kGy,温度60℃,反应时间6 h,体系pH值为1,此时接枝率可达51.2%。红外光谱和扫描电镜表明丙烯酸与竹纤维发生了化学接枝而非物理吸附。热重分析表明共辐照接枝能改善竹纤维的热稳定性,XRD研究发现共辐照接枝后,竹纤维结晶度降低。     

Metal nanoparticles incorporation during the photopolymerization of polypyrrole

In this work we present a route to prepare intrinsically conducting polymer (ICPs)/Silver nanoparticles composite through the photon polymerization process. The method consists to use the transition metals ions assisted by UV light to polymerize the pyrrole monomer. At the same time that the monomer is polymerized the silver ions are reduced and the silver metal particle are produced and incorporated to the polymer matrix. The composite films were characterized by conductivity measurements, UV/vis and FTIR spectroscopy, X-ray diffraction, and scanning electronic microscopy. The morphological properties of incorporated silver nanoparticles were examined with respect to the nature of substrates, exposure time and monomer ratios. Soon after a silver nitrate solution containing Pyrrol is excited by an UV light, a black deposition appears on glass walls or other substrates, such PET (poly(ethylene terephthalate) immersed in the solution, however if the solution is set aside and protected from light, the same black films takes more than 48 h to form. The UV–visible absorption, X-ray diffraction, infrared analysis and conductivity measurements confirm the formation of silver particles and pyrrole polymerization with composite conductivity in the order of 10⁻³ S cm⁻¹.     

甲基丙烯酸甲酯与尼龙接枝共聚反应的研究

研究了过氧化二苯甲酰 (BPO)引发的甲基丙烯酸甲酯与醇溶性尼龙在乙醇中的接枝共聚反应 ,探讨了单体浓度、引发剂浓度对接枝率的影响。并由红外光谱、X射线衍射分析对接枝共聚产物进行了结构表征     

界面聚合法合成苯胺与邻甲氧基苯胺的樟脑磺酸掺杂共聚物及其表征

采用界面聚合法在樟脑磺酸存在的状态下合成了聚苯胺、聚邻甲氧基苯胺以及苯胺与邻甲氧基苯胺的共聚物.利用红外光谱,紫外可见吸收光谱,电子扫描微电镜,X-射线粉末衍射,循环伏安,电导率测试等手段对聚合物进行了表征,初步探讨了单体配比对共聚物形貌、结构及性能的影响.结果表明,界面聚合法合成的上述各聚合物均呈现微米级颗粒状分布,颗粒直径大多在100nm以内;共聚后聚合物的结晶性能下降;循环伏安及电导率测试结果表明,随着聚合物主链中邻甲氧基苯胺结构单元的增加,聚合物的电化学活性及电导率呈下降趋势.     

Diffusion-based model to predict the conservation of gratings recorded in poly(vinyl alcohol)-acrylamide photopolymer

Photopolymers are interesting materials for use in recording information in holography. We study the holographic behavior and stability of volume holograms recorded in poly(vinyl alcohol)--acrylamide photopolymers with and without a cross linker. Using a first-harmonic diffusion model, we analyze the residual monomer that remains when volume diffraction gratings are recorded in photopolymer materials. The importance of this residual monomer to the stability of the gratings is evaluated.     

液晶基元直接横挂于主链上的液晶共聚物的合成与研究

以含液晶基元的单体２，５－双（４－甲氧基苯甲酰氧基）苯乙与苯乙烯通过自由基共聚合反应，首次合成了一系列含液晶性和非液晶性两种序列结构的共聚物。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，发现单体和共聚物（只有ＣＰ－５和ＣＰ－６）有很好的热致液晶性。随共聚物中介晶单体单元含量的增加，共聚物玻璃化转变温度Ｔ和热分解温度Ｔ呈规律变化。     

聚6-氨基己酸-β-丙氨酸的合成及降解行为研究

采用熔融缩聚法制备了一种新型可降解的6-氨基己酸(6N)和β-丙氨酸(βA)的二元共聚物(PAA),并研究了该共聚物的性能。采用红外光谱分析(FT-IR)、X射线衍射分析(XRD)、差示扫描量热分析(DSC)、热重分析(TGA)等手段对其结构进行了表征,结果表明,所合成的材料是2种单体的聚酰胺共聚物;随β-丙氨酸含量的增加,共聚物的结晶度、熔融温度呈先减小后增大的趋势,而分解温度呈依次减小的趋势,当共聚物中2种单体摩尔比为1∶1时,其为无定形共聚物。共聚物在去离子水中的降解实验结果表明,材料具有良好的降解性能;不同单体比例合成的共聚物中,共聚物的降解速率与共聚物的结晶度成反比,当聚合物中2种单体摩尔比为1∶1时,聚合物的降解速度最快,2周后几乎完全降解;整个降解过程中,降解液的pH值都维持在相对稳定的水平。在环保方面,该材料可望有良好的应用前景。     

工艺条件对氧化铍凝胶注模坯体强度的影响

研究单体浓度（AM）、单体/交联剂比例（AM/MBAM）、反应温度和固相体积分数等工艺条件对氧化铍凝胶注模坯体强度的影响,并从自由基聚合反应角度分析各因素对纯凝胶强度和均匀性的影响的原因,得出各因素较合适的参数范围。结果表明纯凝胶和坯体强度随着单体浓度的增加而增加,但过高的单体浓度会使结构均匀性变差,因此单体浓度较合适的范围为10%～20%（质量分数）;随着AM/MBAM比例的增加,坯体强度降低,均匀性下降,AM/MBAM比例应控制在20∶1与30∶1之间;随着反应温度的升高,凝胶强度起初逐渐减低而后又升高,但凝胶均匀性则为先逐渐增加而后又减低,反应温度应控制在20～35℃范围内;随着固相体积分数的增加,凝胶注模坯体强度逐渐下降,但均匀性却升高,因此在满足坯体强度要求的前提下,固相体积分数应尽可能的较高。     

TiN/聚吡咯纳米复合材料的制备及表征

采用氨解法制备了纳米氮化钛(TiN)粉体,对纳米TiN粉体进行表面改性,使其均匀分散到吡咯单体中.采用原位聚合法制备了TiN/聚吡咯(PPy)纳米复合材料.对合成的复合材料用X射线衍射(XRD)、透射电镜(TEM)、傅立叶变换红外光谱(FT-IR)、四探针测试仪等方法进行了表征与检测.结果表明:PPy成功地包覆在TiN纳米颗粒表面,形成了纳米TiN/PPy复合材料.复合材料具有优良的电性能.