Papers by Keyword: Mesophase

Abstract: The transition from the glass to the highly elastic state in polydiethylsiloxane (PDES) is not reflected on the temperature dependences of the relative permittivity, the dielectric loss tangent, and the specific volumetric electrical conductivity. But, the peak of the current of thermostimulated depolarization (TSD) is fixed in the temperature range of the transition to the highly elastic state. The peak of the TSD current at T ~ 130K indicates a continuous amorphous phase formation in the experimental conditions. The maximum value of the TSD current directly depends on the content of the amorphous phase in the polymer. The cooling of the polymer in an electric field reduces the magnitude of the peak. Exposure in the mesophase leads to an almost complete absence of thermopolarization effects near the glass transition temperature. This peak of the TSD current in the absence of preliminary polarization is characteristic, presumably, only for flexible-chain polymers where structural units have pyroelectric properties. Under certain conditions, PDES demonstrates itself as an active dielectric in the temperature range of 90 - 180K.

Abstract: The mesophase (iron aluminate, etc.) in steel slag was extracted by potassium hydroxide-sucrose (KOSH) solution method. The effects of partical size of steel slag, temperature and time of extraction on dissolution of mesophase phase were studied. The composition and morphology of the residue were analyzed by XRD and SEM. The results show the mesophase in steel slag powders (the weight was and the fineness was) could be fully dissolved when 4.00 g sample with a fineness about 600m²/kg is used and extraction temperature is kept at 90 ^oC, however, other minerals in the steel slag could be hardly dissolved. The reason might be for that, in alkaline environment which provided by potassium hydroxide, the replacement of ions were took place between the mesophase in steel slag and the organic ligands formed by sugar and potassium hydroxide, and through the adsorption and polarization between ligand and steel slag surface, it will result in the decrease of activation energy of iron aluminate.

Abstract: Liquid crystals (LCs) are compounds that have properties between isotropic liquids and solid crystal materials. Although there is not a parameter to predict this behavior, the liquid crystals reported until now have common characteristics, for example rigid groups such as columns or rods within its structures, and long hydrocarbon chains that give flexibility. In this work we report the synthesis and characterization of LC N,N'-(1,4-phenylene bis (methanylylidene)) bis (4-(hexyloxy) aniline). The compound was characterized by infrared (IR), raman and ¹H-nuclear magnetic resonance (¹H-NMR) spectroscopies. The mesomorphic properties were determined by Differential Scanning Calorimetry (DSC) and Polarized Optical Microscopy (POM). The compound N,N'-(1,4-phenylene bis (methanylylidene)) bis (4-(hexyloxy) aniline) was obtained with a yield of 87 % and purity of 99.9 % determined by elementary analysis. The POM study revealed that this compound have a typical low molecular weight liquid crystal behavior. At temperatures of 157 and 174 °C typical mesophases of liquid crystals were observed; the phase transitions were analyzed by DSC. The POM images reveal the typical birefringence of liquid crystal behavior and different anisotropic textures of smectic and nematic mesophases, these textures are characteristic of the benzylideneanilines or Schiff bases.

Abstract: This article have reviewed the preparation processes, flow path and methods of today's high-performance mesophase asphalt-based carbon fiber, and illustrated the advantages of preparation of high performance asphalt-based carbon fiber. Besides, today's main methods of preparation of asphalt-based carbon fiber have been found, and the key problems of preparation of high performance carbon fiber have been figured out.It is very complex and difficult to control accurately. Preparation of mesophase asphalt-based carbon fiber is mainly reflected in the following points: (1) The selection of asphalt; (2) The quality of the spinning; (3) The effect of oxidation treatment; (4) The temperature during carbonization and graphitization process.

Abstract: In this study, a triphenylene-based discotic liquid crystal 3,6-dicarbethoxy-2,7,10,11-tetra-pentyloxytriphenylene was synthesized. The chemical structure was characterized by FTIR, 1HNMR.The mesophases of the material synthesized here was characterized by using polarizing optical microscopy (POM), differential scanning calorimetry (DSC). It was found that the compound displayed columnar phase during cooling at 164.7 °C and the columnar phase can be preserved even at room temperature. The charge transportation properties of the compound were measured by using time-of-flight method.

Abstract: A side chain triphenylene-based polysiloxane were synthesized from 2-hydroxy-3-Methoxy-6,7,10,11–tetrapentyloxy-triphenylene.2-hydroxy-3-Methoxy-6,7,10,11–tetrapentyloxy triphenylene was synthesized via the common synthisis route including the Williamson Etherification of catechol, the iodination of 1,2-dipentyloxybenzene, the Ullman Coupling and the coupling of 3,3'-4,4'–tetrapentyloxy diphenyl and methoxy-phenol; 2-allyloxyl-3-Methoxy-6, 7, 10, 11–tetrapentyloxytriphenylene was synthesized by the etherification of 2-hydroxy-3-Methoxy-6,7,10, 11–tetrapentyloxytriphenylene and allyl bromide; the polysiloxane was synthesized by addition of 2-allyloxyl-3-Methoxy-6,7,10,11–tetrapentyloxytriphenylene and polydimethylsiloxane. The structures of the compounds were determined by FTIR and 1HNMR. Mesophase and their structural orders were determined using a polarized optical microscope and a differential scanning calorimeter.

Abstract: Cholesteric liquid crystals elastomers have been extensively studied during the last two decades. They showed Bragg-reflection in visible, Infrared and even UV wavelength Range and a particular circular polarization. Their special helical structure and the adjustment of pitch made them suitable for using as optical thin films. In this study, two kinds of mesogenic monomers undecylenate cholesteryl ester (M₁) and p-phenylene di-4-(allyloxyl) benzoate (M₂) were synthesized. Then the two monomers were fixed onto poly- (methylsiloxane) backbone by grafting polymerization using Dicyclopentadienylplatinum (II) Chloride as catalyst. A series of side-chain polymers with different monomer densities produced by the reaction of hydropolysiloxane and M₁/M₂ with different molar ratios were obtained. The synthesized polymers were characterized by IR, H1NMR and GPC. The mesophases were characterized by using differential scanning calorimetry (DSC), polarizing optical microscopy (POM).

Abstract: In this paper, (E)-4-(2-(4-(allyloxy) phenyl) diazenyl) benzoic acid and (E)-4-(2-(4-(hexyloxy) phenyl) diazenyl) benzoic acid were synthesized through diazotize-coupling reaction and etherification. The structures of these compounds were characterized by the methods of 1H-NMR and FTIR. Phase transition temperature was measured by DSC, and the phase behaviors were studied by the polarizing microscope. Both of them had mesomorphic phase. And the mesophase temperature of (E)-4-(2-(4-(hexyloxy) phenyl) diazenyl) benzoic acid ranged from 224.9 °C to 265.4 °C.

Abstract: A series of novel liquid crystal were synthesized with alkyloxyben- zimidoylbenzoic acid (CnABOH) and poly(4-binylpridind) (PVP) through hydrogen bond self-assemble between carboxyl groups of alkyloxybenzimidoylbenzoic and nitrogen of PVP. PVP was used as a hydrogen bond acceptor polymer. The CnABOH (n is the number of carbon atom) had been used as H-bond donor. The existence of H-bond was confirmed used FTIR spectroscopy. Optical microscopy was used to investigate liquid crystalline behaviors. The mesophases of the complexes (PVP-CnABOH) were obviously different from LC behaviors of the CnABOH. With increasing length of terminal group, the melting temperature reduced and the temperature range of the LC mesophase increased. For instance, while the number of carbon atom increased from 3 to 8, the melting temperature reduced from 180°C to 156°C and the range of LC mesophase increased from 36°C to 84°C.

Abstract: A three-ring containing bent-core compound 1,3-phenylene-bis(4-butoxybenzylidene amine) was synthesized and characterized with differential scanning calorimetry and polarized optical microscopy. It exhibited mesophases in the temperature range of 48-54oC for the first cyclic heating and cooling. Our results demonstrated that three-ring containing bent-core molecules can form mesophases.