星形液晶的分子结构对其有序排列的影响

以1,2,4-丁三醇(C)为手性中心,4’-(4-(三氟甲基苯甲酸基)联苯)羧酸(B1)、6-(4-(4-乙氧基苯甲酸基)苯)己二酸单酯(B2)为侧臂,采用N,N'-二环己基碳化二亚胺/4-二甲氨基吡啶(DCC/DMAP)成酯法,合成了均臂星形与杂臂星形液晶FJ0~FJ3。通过红外光谱、核磁共振、偏光显微镜、差示扫描量热、变温X射线衍射等手段对所合成的星形液晶的分子结构及其有序排列进行了研究。结果表明,手性中心使均臂星形液晶(FJ0和FJ3)产生螺旋状的有序排列,而杂臂星形液晶(FJ1和FJ2)并未受手性中心的影响形成螺旋结构,而是形成了一维有序的向列相结构。     

主链柔顺性对侧链液晶聚合物液晶性能的影响

由对羟基苯甲酸与对羟基甲醚反应得到了４－甲氧基－４’－羟基苯甲酸苯酯（ＭＰＨＢ）,ＭＰＢＨ再分别与环氧氯丙烷和甲基丙烯酰氯反应生成４－甲氧基－４’－（２,３－环氧丙基氧）苯甲酸苯酯（ＭＰＥＢ）和４－甲氧基－４’－甲基丙烯酰氧苯甲酸苯酯（ＭＰＭＡＢ）。用阳离子和自由基聚合法聚合得到了具有相同液晶元而主链结构和间隔基不同的聚合物ＰＭＰＥＢ和ＰＭＰＭＡＢ。用ＤＳＣ、热台偏光显微镜和Ｘ射线衍射仪对合成的聚     

液相色谱法测定食品包装用油墨中11种光引发剂的含量

目的 建立油墨中光引发剂的检测方法，从源头控制食品包装的安全。方法 油墨样品经乙酸乙酯和乙腈超声提取，体积分数为20%的乙腈溶液定容，固相萃取柱萃取后用乙腈定容，使用液相色谱进行测定。结果 11种成分在各自范围内线性关系良好（R≥0.999 5），平均加样回收率为90.0%～95.0%，相对标准偏差（n=6）小于3.5%。结论 建立了液相色谱同时测定油墨中2-甲基-1-(4-甲基硫代苯基)-2-(4-吗啉基)-1-丙酮、1-羟基环己基苯基酮、2-苯甲酰基苯甲酸甲酯、4-二甲氨基苯甲酸乙酯、4,4’-二（N,N-二甲氨基）二苯甲酮、安息香双甲醚、4-甲基二苯甲酮、4,4’-二（N,N-二乙氨基）二苯甲酮、对二甲氨基苯甲酸异辛酯、2-异丙基硫杂蒽酮、2,4-二乙基噻唑酮的方法。     

4,4’二(4-烯丙氧基苯甲酸)苯酯双功能基团液晶体的制备与性能

以3-溴丙烯、4-羟基苯甲酸和对苯二酚为主要原料,经Williamson醚化、羧酸酰化和酯化反应制备了4,4'-二(4-烯丙氧基苯甲酸)苯酯双功能基团液晶单体,通过FT-IR,1H-NMR,13C-NMR对其结构进行了表征.用DSC,XRD,偏光显微镜((POM)研究了单体的液晶性能,结果表明该单体熔点为164℃,清亮点为244℃,为向列相液晶.     

有机可溶性聚酯酰亚胺的合成及其液晶分子取向特性研究

采用偏苯三酸酐酰氯（TMAC）与乙二醇反应制备了含有酯键的乙二醇双苯甲酸酯-3,3’,4,4′-四酸二酐（TMEG）。然后采用该二酐单体分别与芳香族二胺单体,包括4,4′-二胺基二苯甲烷（MDA）、4,4′-二胺基二苯胺（NDA）、1,4-双[2-（4-胺基苯基）-2-丙基]苯（BisP）以及1,3-双[2-（4-胺基苯基）-2-丙基]苯（BisM）通过两步化学亚胺化工艺制备了可溶性聚酯酰亚胺（PEsI）树脂。凝胶渗透色谱（GPC）测试结果显示,该系列PEsI树脂的数均分子量（M_n）在6.21×10⁴～1.64×10⁵ g/mol,表明TMEG具有较高的反应活性。该系列PEsI树脂在极性非质子性溶剂,如N-甲基吡咯烷酮（NMP）、N,N-二甲基乙酰胺（DMAc）等中具有良好的溶解性,但在低极性溶剂,如乙二醇丁醚（BC）体系中则不溶解。采用PEsI/NMP/BC体系配制了PEsI液晶取向剂,并以此装配了液晶盒。测试结果显示,基于TMEG的PEsI取向膜具有良好的耐热稳定性,其5%失重温度超过了400℃,玻璃化转变温度（T<...     

基于1,2,4-三羧基-3-羧甲基环戊烷二酐的可溶性聚酰亚胺垂直取向剂的制备及性能

采用1,2,4-三羧基-3-羧甲基环戊烷二酐（TCA）、4,4’-二氨基二苯甲烷（MDA）及长侧链二胺4-十二烷氧基苯甲酸酯联苯酚-3’,5’-二胺基苯甲酸酯（DBPDA）共聚制备了一系列的聚酰亚胺。并对其溶解性能、透光性能及取向性能进行了测试。结果显示,聚酰亚胺在有机溶剂中可溶,成膜后紫外透光率较高,在波长400 n...     

侧链含有两种介晶基元的聚硅氧烷类液晶聚合物的制备与性能

合成了侧基带有两种介晶基元的聚硅氧烷类系列液晶聚合物（P1－P5），所用介晶单体M1为4－联苯二酚基－4’－（2－乙基已酰基）－4－烯丙氧基苯甲酸酯，M2为4－烯丙氧基苯甲酰氧基－4’－甲氧基苯，它们介晶区间分别为39℃和7．9℃。只含有单体M1的聚合物P1和只含有单体M2的聚合物P5的介晶区间分别为70．8℃和75．1℃；但是同时含有不同摩尔比的M1和M2的液晶聚合物P2－P4的介晶区间为240－250℃，比只含有一种介晶基元的P1或P5拓宽了约170℃，所有聚合物均低于室温就有液晶性能，且耐热性达310℃以上，属于非晶近晶织构。     

基于季戊四醇的二代硅碳烷液晶树状物--端基含36个丁氧基偶氮苯基团

以基于季戊四醇的二代硅碳烷树状氯化物PCSi-2G-Cl为脚手架、4一-丁氧基-4’-羟己氧基偶氮苯（M—C4）为介晶基元,合成了以季戊四醇为核、端基含36个丁氧基偶氮苯的新型硅碳烷液晶树状物PCSi-2GC4。利用红外光谱（IR）、核磁共振（^1H NMR）、元素分析（EA）、偏光显微镜（POM）和差示扫描量热法（DSC）进行了表征。PCSi-2G-C4与M—C4同为向列相,说明树状物相态由介晶基元相态决定。PCSi-2G-C4的熔点比M—C4降低13℃,清亮点比M—C4降低15℃。     

含酒石酸基元的液晶单体及其聚合物的合成与表征

合成了一种以酒石酸为中心的新型工字型液晶单体2,3-二乙酰氧基-1,4-丁二酸对烯丙氧基苯甲酸对苯二酚酯(M1),将其与手性液晶单体4-烯丙氧基苯甲酸胆甾醇酯(M2)共聚,得到侧链液晶聚合物P1～P8。通过红外光谱(FT-IR)、核磁共振(1H-NMR)、偏光显微镜(POM)、差示扫描量热分析(DSC)和X射线衍射(XRD)等手段对所获单体及聚合物的结构和液晶相行为进行了表征。结果表明,液晶单体M1具有近晶相扇形、纹影织构,手性单体M2具有胆甾相油丝织构。聚合物P1～P8出现胆甾相的Grandjean织构,随着单体M1含量的增加,聚合物P1～P8的Tg呈上升趋势,液晶区间变窄。     

含氟席夫碱型环氧液晶聚合物的合成与表征

合成了席夫碱型含氟液晶单体(4-烯丙氧基苯甲酸)-2-甲氧基-4-三氟甲氧基苯胺亚甲基-苯酯(M)和环氧液晶单体(4-烯丙氧基苯甲酸)-4-(2,3-环氧丙氧基)-苯酯(E),将它们接枝共聚到含氢聚硅氧烷上,得到系列含氟席夫碱型环氧液晶聚合物PI~PVI。采用红外光谱、核磁共振、差示扫描量热、热重分析、偏光显微镜和X射线衍射等手段对单体及聚合物的结构和液晶性能进行表征。结果表明,聚合物PI~PVI呈现向列相。从PI到PVI随着单体M含量的减少,聚合物玻璃化转变温度(T_g)和清亮点(T_i)均呈下降趋势。该系列聚合物热稳定性良好,液晶区间在36.4~177.5℃之间。     

Influence of pretilt angle on disclination lines of liquid crystal lens

This article investigates the effect of pretilt angle on disclination lines of liquid crystal (LC) lenses. When the pretilt angle of LCs is higher than 7°, the disclination lines are reduced and are moved to the boundary of the LC lens. The disclination lines at the boundary do not influence the focused beam profile of the LC lens. As the pretilt angle of LCs further increases, the disclination lines at the boundary become almost invisible. However, the interference rings become asymmetrical. The response time of an LC lens with a pretilt angle higher than 7° is ～60% of the conventionally homogeneous LC lens. This value is a result of the decrease in the rotation angle of the LCs and the reduced disclination lines.     

后处理工艺对POSS-PMMA_8改性凝胶聚合物电解质性能的影响

为解决凝胶聚合物电解质(GPE)的离子电导率低、力学性能差等问题,通过静电纺丝制备星型笼型低聚倍半硅氧烷-聚甲基丙烯酸甲酯(POSS-PMMA_8)改性聚甲基丙烯酸甲酯-聚丙烯腈-聚偏氟乙烯(PMMA-PANPVDF)得到聚合物纺丝薄膜(POSS-PMMA_8/PMMA-PAN-PVDF)M1,将聚合物纺丝薄膜M1在120℃热处理得到聚合物纺丝薄膜M2,或热压并预氧化处理得到聚合物纺丝薄膜M3,将其浸泡于电解液中活化得到POSS-PMMA_8/PMMA-PAN-PVDF的GPE。对不同状态聚合物纺丝薄膜M1、M2、M3的形貌、孔隙率、吸液率、力学性能及其GPE的电导率和电化学稳定窗口进行测试。结果发现,相比于M1,M2的拉伸强度及GPE的电导率分别提高9.2%及181.1%,电化学窗口增至5.3 V;而M3的拉伸强度和GPE电导率分别较M1增加193.7%、20.2%,电化学窗口增至5.5V。     

Preparation of electrospun nanofibers of star-shaped polycaprolactone and its blends with polyaniline

The electrospun nanofibers of synthetic star-shaped poly(?-caprolactone) (PCL) and its blends with polyaniline (PANI) were prepared. We utilized the advantages of star-shaped PCL and benefits of electrospinning method for obtainment of the uniform nanofibers with improved properties for tissue engineering. Biodegradable star-shaped PCL with four arms was synthesized by Sn(Oct)₂-catalyzed ring-opening polymerization (ROP) of ?-caprolactone (CL) from a pentaerythritol core. The chemical structure of star-shaped PCL was investigated by FTIR, and average molecular weight of polymer was determined by ¹HNMR (about 38000 g mol^?1). Thermal behavior of star-shaped PCL was also studied by Thermogravimetric Analysis (TGA). Moreover, the cyclic voltammetry (CV) measurement confirmed the preparation of electroactive nanofibers. The scanning electron microscopy (SEM) was also used to investigate the morphology of electrospun nanofibers produced from star-shaped PCL and its blends with PANI with different feed ratios. The presence of PANI resulted in fibers with diameters less than 100 nm and significant decrease of bead formation.     

Efficient angular spectrum decomposition of acoustic sources. II. Results

For pt.I see ibid., vol.40, no.3, p.238-49 (1993). Results of angular spectrum computations are presented for three applications: general decomposition, pressure field calculation, and modeling of pulse-echo measurements. Wherever possible, analytical (exact) results are used as reference for the decomposition results. This permits the accuracy of the angular spectrum decomposition to be evaluated for specific choices of M and N where M is the number of samples across the maximum characteristic length, d, of the source region and N is the total number of samples along each side of the source decomposition plane, and for both sampling techniques. Based on the results for the three applications, guidelines for choosing M and N are presented in a graphical format.     

Studying viscoelastic properties of liquid crystals during nematic-isotropic phase transition by low-frequency ultrasound probing of small-volume samples

The velocity of propagation and the coefficient of absorption of ultrasound in liquid crystals (LCs) in the vicinity of the phase transition from a nematic phase (N) to the isotropic liquid (I) has been studied in samples with a volume of 0.15 cm³ using an acoustic resonance technique at frequencies in the range from 0.68 to 1.63 MHz. An analysis of the results of acoustic measurements provides information on the characteristics of phase transition and critical anomalies in the viscous properties of LCs in the N-I phase transition region. The proposed acoustic method offers good prospects for the rapid investigation of small volumes of mesogenic compounds.     

Chemically Responsive Gels Prepared from Microspheres Dispersed in Liquid Crystals

Liquid‐crystalline materials are a promising class of stimuli‐responsive materials that have been demonstrated to undergo surface‐induced orientational ordering transitions that can be highly sensitive and specific to chemical species. However, past studies demonstrating surface‐induced transitions in liquid crystals (LCs) have employed thin films of low‐molecular‐weight LCs that are difficult to stabilize (due to dewetting of the LC on a surface). Here, it is reported that it is possible to prepare liquid‐crystalline gels using a mixture of polystyrene microspheres and nematic LCs that undergo changes in orientational order, and thus optical appearance, in response to exposure to specific chemical compounds. These colloid‐in‐liquid‐crystal (CLC) gels are mechanically stable and can be molded on chemically functionalized surfaces into thin films containing micrometer‐sized LC‐rich domains that span the two interfaces of the gels. In contrast to other reports of LC gels, where the presence of a polymeric or self‐assembled small‐molecule gelator network within a nematic LC frustrates ordering transitions from propagating through the gels over distances, it is demonstrated that thin films of CLC gels, when supported on chemically functionalized surfaces, do undergo easily visualized ordering transitions upon exposure to organophosphonate compounds. Because these optically responsive CLC gels are mechanically robust and can be molded, this class of composite LC material may be broadly useful for the design of chemically responsive LC devices.     

热致可逆变色胆甾液晶聚合物的制备和光学性能研究

合成了两种胆甾液晶单体,4-烯丙氧基苯甲酸胆甾醇酯M1和4-{4-[(4-烯丙氧基)-苯甲酰氧基]丁氧羰基}苯甲酸胆甾醇酯M2。将两种单体按一定比例与含氢聚硅氧烷(PMHS)共聚得到了一系列侧链液晶聚合物P1-P6。采用红外光谱(FT-IR)、核磁共振(1 H NMR)、差示扫描量热(DSC)、偏光显微镜(POM)和X射线等手段对单体及聚合物的结构、液晶性能和相行为进行了表征。通过分析表明单体M1、M2和聚合物为热致胆甾型液晶,聚合物在常温具有选择性反射现象,在升温—降温—再升温的过程中反射波长随温度升高发生蓝移,且聚合物具有良好的热稳定性和可逆变色性。     

Synthesis and investigation of the properties of a star-shaped polysilane

The intermediate monomer of a star-shaped polymer's cyclosiloxane core, was prepared from CH₃HSiCl₂ and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane(D₄^vi) through the basic method of hydrosilylation reaction. Then, a star-shaped polysilane [poly(core-methylphenyl-diphenyl)silane] was synthesized by the classical Wurtz coupling reaction. Futhermore, UV absorption, fluorescent spectrum, UV-resistant stability and thermal properties of the star-shaped polysilane were investigated. Results reveal that star-shaped polysilane possesses good UV-resistant stability, favourable thermo-oxidative stability and strong fluorescence emitting near 400 nm.     

Tunable Diffraction Gratings from Biosourced Lyotropic Liquid Crystals

Diffraction gratings are important for modern optical components, such as optical multiplexers and signal processors. Although liquid crystal (LC) gratings based on thermotropic LCs have been extensively explored, they often require expensive molecules and complicated manufacturing processes. Lyotropic LCs, which can be broadly obtained from both synthetic and natural sources, have not yet been applied in optical gratings. Herein, a facile grating fabrication method using a biosourced lyotropic LC formed by cellulose nanocrystals (CNCs), a material extracted from plants, is reported. Hydrogel sheets with vertically aligned uniform periodic structures are obtained by fixing the highly oriented chiral nematic LC of CNCs in polymer networks under the cooperative effects of gravity on phase separation and a magnetic field on LC orientation. The hydrogel generates up to sixth-order diffraction spots and shows linear polarization selectivity, with tunable grating periodicity controlled through LC concentration regulation. This synthesis strategy can be broadly applied to various grating materials and opens up a new area of optical materials from lyotropic LCs.     

Limit cycle analysis of nonsmooth aeroelastic system of an airfoil by extended variational iteration method

The variational iteration method (VIM) was extended to solve the aeroelastic system of an airfoil with both cubic and nonsmooth stiffnesses (a piecewise freeplay), expressed by integral-differential equations. Limit cycle (LC) frequency and amplitude are unknown to be updated at every iteration stage. If the VIM is routinely applied, the LC solution needs to be embedded into both the integrals and the freeplay, which can result in two intractable problems: (1) the integrals lead to coupled terms between frequency and amplitude and (2) the Fourier expansion of the freeplay cannot be realized. In order to tackle these problems, the solution obtained at the previous iteration rather than the current unknown one is applied to the freeplay and the integrals. By this means, the frequency and amplitude are decoupled, and the freeplay can be expanded as Fourier series. Numerical examples show that very accurate LC solutions can be obtained by the presented method. This method is suitable for solving LCs of nonlinear dynamical systems with nonsmooth nonlinearities.