Micro-segregated layer structures generated by liquid crystalline dimers possessing an oligo(ethylene glycol) spacer and two terminal alkyl chains

Liquid crystalline dimers consisting of two rodlike cores, two terminal alkyl chains and an oligo(ethylene glycol) spacer were synthesized. Their phase behaviors and structures were investigated by polarized optical micrograph (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). These liquid crystalline dimers generated unconventional smectic layer structures in which the alkyl and oligo(ethylene glycol) chains micro-segregated in the chain layers.     

聚醚酰亚胺和热致性液晶高分子原位复合材料的研究进展

综述了近年来聚醚酰亚胺和热致性液晶高分子共混形成原位复合材料的研究进展。液晶高分子在共混物中既起到增强剂的作用。又起到加工助剂的作用。应用Taylor理论可描述液晶分散相在基质高分子中的成纤过程。讨论了各自聚合物以及共混物的流体动力学行为和聚合物间的相容性、混合程序、混合物组成等因素对原位复合材料的形态和力学性能的影响。     

Internal structure and physical properties of thermotropic liquid crystal polymer/poly(ethylene 2,6-naphthalate) composite fibers

Thermotropic liquid crystal polymer (TLCP)/poly(ethylene 2,6-naphthalate) (PEN) composites and their fibers were prepared by using melt compounding and spin-draw process. Thereafter, they were additionally drawn by various drawing methods. As TLCP contents increased, melt flow index was increased and shear viscosity was decreased because TLCP fibril structure of rigid backbones was formed during melt compounding. Molecular orientation and crystalline structure of the TLCP/PEN composite fibers were improved as a function of draw ratio and the heat–laser drawing method gave synergic effects on internal structure of the TLCP/PEN composite fibers. Thermal stability of the TLCP/PEN composite fiber was improved significantly by incorporating small amount of TLCPs.     

Synthesis,crystal growth and characterization of novel semiorganic nonlinear optical crystal: Dichlorobis(l-proline)zinc(II)

Single crystals of the semiorganic material, dichlorobis(l-proline)zinc(II) (DCBPZ), were grown from aqueous solution. The grown crystals were tested by single crystal X-ray diffraction, energy-dispersive spectrometry, FT-IR, UV–vis and TG–DTA. The structural prefection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The dielectric and mechanical behavior of the specimen was also studied. The SHG efficiency of DCBPZ is three times greater than that of KDP. Measuring transmittance of DCBPZ permitted the calculation of the refractive index n, the extinction coefficient K and both the real ?_r and imaginary ?_i components of the dielectric constant as functions of photon energy. The optical band gap of DCBPZ is 4.8 eV.     

Phase transitions of liquid crystalline polyesters: Poly(heptane-1,7-diyl-4,4′-biphenyldicarboxylate)

Wide-angle X-ray scattering was applied to investigate the non-isothermal and isothermal phase transitions of poly(heptane-1,7-dyil-4,4′-biphenyldicarboxylate). It is suggested that the isotropic–smectic (I–S) transition is controled by a nanophase separation with a critical point T_ns=151 °C. Nanophase separation is followed by a first-order S–Cr (crystal) transition. At isothermal conditions above T_ns only S phase exists, whereas below it the S phase appears first and the Cr phase grows from the S by nucleation and three-dimensional crystal growth.     

Anisotropic focusing characteristics of microdomain structures within crystalline Sr(0.61)Ba(0.39)Nb2O6: the crystal ball

We report the anisotropic focusing characteristics of a spherically configured region of microdomains that have been induced within a cubic-shaped crystal of Ce-doped Sr(0.61) Ba(0.39) Nb(2) O(6). The internal spherical structure focuses extraordinary polarized light, but not ordinary polarized light. The spherical region, which is easily observed via scattering, is formed as the crystal cools after a repoling cycle through the Curie temperature, with an applied field. Analytic modeling of the thermal gradients that exist within the crystal during cooling reveals a small (<1 degrees C) temperature difference between the central and the outside regions. The similarity in shape between these temperature profiles and the observed scattering region suggests a possible mechanism for the growth of this spherical microdomained structure.     

Characterization and investigation of the mesogenic, thermo-morphologic and thermotropic properties of new chiral (S)-5-octyloxy-2-[{4-(2-methylbuthoxy)-phenylimino(methyl]phenol liquid crystalline compound

Synthesis, characterization and investigation of the mesogenic, thermo-morphologic and thermotropic properties of a new chiral liquid crystalline compound are presented in this work. This new compound has prolate molecules and exhibits the chiral smectic C* mesophase in a sufficiently large temperature interval. Two types of solid crystalline phases have been found in this compound. Typical textures and temperatures of the direct and reverse phase transitions, taking place in the compound, are given. Typical peculiarities for the first-order transition between the smectic C* mesophase and isotropic liquid have been observed.     

Studies on growth and characterization of an NLO crystal: L-alanine hydrogen chloride (LAHC)

A nonlinear optical (NLO) salt viz. L-alanine hydrogen chloride (LAHC) has been synthesized and solubility of the synthesized salt in de-ionized water was determined at different temperatures. Single crystals of L-alanine hydrogen chloride (LAHC) salt were grown by solution method with slow evaporation technique. The grown crystals were characterized by single crystal X-ray diffraction (XRD) and powder XRD analyses to study the crystal structure. The crystallinity of LAHC crystal was confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. FTIR study was used to confirm the presence of various functional groups in the grown crystals. UV–visible transmittance spectrum was recorded to study the optical transparency of LAHC crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz–Perry powder test. The density of LAHC crystal was determined by floatation method. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to TG/DTA analyses. The dielectric behavior of the sample was also studied.     

非线性光学晶体MnHg(SCN)4(C2H6SO)2的热学和光学性质的测定

制备了一种新型非线性光学晶体二甲亚砜合硫氰酸汞锰(分子式MnHg(SCN)4(C2H6SO)2,简称MMTD).用热重法、差热分析法、差示扫描量热法、热机械分析法、分光光度法和红外光谱研究了它的热学和光学性质.MMTD晶体具有较好的物理化学稳定性.在27℃时,它的比热为699.5 J/mol·℃.晶体的热膨胀系数为α1=5.33×10-5/℃,α2=4.51×10-5/℃,α3=3.10×10-5/℃.MMTD晶体的截止波长为375nm;透光波段为375-2560 nm.MMTD晶体在标准紫光波长404nm的透过率为44.18%,高于硫氰酸汞锰(MMTC)晶体.     

Enhanced optoelectronic,thermal, mechanical and third order nonlinear optical properties of dichlorobis(thiourea)zinc(II) crystal: an effect of Phenol red dye

For the first time the growth of dichlorobis (thiourea) zinc(II) (ZTC) monocrystal in presence of Phenol red dye of considerably good size (~13 mm?×?5 mm) has been achieved from aqueous solution using slow evaporation solution technique at room temperature. The solubility was calculated at different temperatures. The crystal structure was confirmed through X-ray diffraction analysis. The crystallinity of the dyed crystals has been enhanced revealed by Powder X-ray diffraction study. The presence of dye was inveterate by FT-IR and FT-Raman spectroscopic studies. The scanning electron microscopy analyses show that the grown crystals with dye are better than pure. Diffused reflectance was measured and optical band gap was calculated found to be enhanced from 4.5 to 4.65 eV for dyed crystals. The enhancement in the PL intensity has been observed in the dyed crystals. DSC study shows that the thermal stability has been remarkably enhanced from 163?°C (pure) to 203?°C (dyed) and various other thermal parameters are calculated. The surface study shows that the grown crystals with dye possess less dislocation than pure. Mechanical strength of the dyed crystal is found to be remarkably enhanced. Third-order nonlinear optical susceptibility (χ3) of PRZTC was found to be 2 times higher than pure. All results suggest that the properties of ZTC crystals grown in presence of dye are enhanced and can be considered as better contender in various nonlinear devices.     

Thermal diffusivity by laser intensity modulation method (LIMM-TD): a novel technique for the determination of thermal diffusivities and conductivities and its application to porous PZT and silica samples

A modification of a technique for the measurement of the thermal diffusivity of thin solid materials is presented. The technique is called Thermal Diffusivity by Laser Intensity Modulation Method (LIMM-TD). It is based on the measurement of the phase retardation of a thermal wave passing through the test material by means of a lead-zirconate-titanate ceramic (PZT) pyroelectric detector. It is not necessary to know either the pyroelectric coefficient of the detector or the intensity of the laser beam. The method was tested on quartz samples to verify its accuracy. It was then applied to the study of several sets of ceramic samples with porosities of 20, 25, and 30%. One sample set was poled and the pores were partially filled with the fluid used during poling. A second set was not poled. The poled porous samples had thermal conductivities intermediate between that of a commercial dense sample and those of unpoled materials. Thermal diffusivities and conductivities were also measured on micron-thickness porous silica samples. The experimental results were compared with calculations using several composite mixing theories.     

Fluorine speciation analysis using reverse phase liquid chromatography coupled off-line to continuum source molecular absorption spectrometry (CS-MAS): identification and quantification of novel fluorinated organic compounds in environmental and biological samples

Driven by increasing demand for the monitoring of industrial perfluorinated compounds (PFCs), the identification of novel fluorine containing compounds (FOCs) and the tracking of organofluorine drugs and their degradation products, there is a clear need for sensitive, fluorine-specific detection of unknown FOCs. Here we report the first ever direct fluorine-specific (speciation) method; capable of individually detecting untargeted FOCs in environmental and biological samples through the application of continuum source molecular absorption spectrometry (CS-MAS) using a commercial CS-AAS. Two model FOCs (2,4,6, trifluorobenzoic acid (TFBA) and 5-fluoroindol-5-carboxylic acid (FICA)) were used, achieving fluorine-specific detection across a range of 0.1 to 300 ng/mL fluorine, corresponding to a limit of detection of 4 pg F and 5.26 nM for both compounds. Both TFBA and FICA showed a similar response to CS-MAS detection, potentially enabling the quantification of fluorine content in novel FOCs without having molecular standards available. This paper also reports the use of reverse-phase high performance liquid chromatography (RP-HPLC) coupled off-line with CS-MAS for the identification of single organofluorines in a mixture of FOCs via fraction collection. The linear range of both FOCs was determined to be from 1 to 500 ng/mL. The limits of detection of those species were just above 1 ng/mL (100 pg) and can therefore compete with targeted analytical methods such as ESI-MS. Finally, as a proof of principle the analysis of a fluoride-containing groundwater sample from Ghana demonstrated that this method can be used in the detection of novel FOCs, with identification achieved through parallel ESI-MS. Coupled HPLC-CS-MAS/ESI-MS is the first analytical methodology capable of selectively detecting and identifying novel FOCs, making possible the quantification of all fluorine containing compounds in one sample. This is the necessary analytical requirement to perform fluoronomics.