排序方式: 共有54条查询结果,搜索用时 46 毫秒
1.
Lightly cross-linked anisotropic networks with uniaxial and π/2 twisted orientations were produced by photopolymerization of monotropic mixtures containing liquid crystal mono and diacrylates. In this way the polymer backbone was immobilized and became decoupled from the motion of the mesogenic side groups. The networks showed very good reversibility and even after becoming isotropic, upon cooling, the initial orientation was recovered. In the same way, in the presence of electric fields the mesogenic groups could be reoriented in the direction of the electric field, reverting back to the initial orientation on removal of the field at a rate comparable with those observed in the monomeric state. Combining viscoelastic measurements with the dielectric behaviour of the monomeric liquid crystal and the anisotropic network, a comparison between the internal and bulk rotational viscosities was also made. 相似文献
2.
Abstract The dielectric relaxation of the liquid crystal 4-n-pentyl-4′-cyanobiphenyl (K15) in the presence of an anisotropic network has been studied. Anisotropic networks containing K15 molecules were prepared by in situ polymerisation of liquid-crystalline diacrylate molecules in a mixture containing K15. By changing the network concentration, the effect of the network molecules on the behaviour of the K15 molecules, which were not chemically attached to the network, was investigated. With increasing network concentration it was found that the mean relaxation times of K15 molecules shifted to lower temperatures and that their distribution became broader. The activation energy associated with the relaxation, however, remained almost constant before showing some increase at high network concentrations. 相似文献
3.
R. A. M. Hikmet 《Liquid crystals》2013,40(11-12):1407-1418
A Commentary on the paper “Anisotropic gels and plasticized networks formed by liquid crystal molecules”, by R. A. M. Hikmet. First published in Liquid Crystals, 9, 405–416 (1991). 相似文献
4.
Koruyucu Elif Ekici Selcuk Karakoc T. Hikmet 《Journal of Thermal Analysis and Calorimetry》2021,145(3):1303-1315
Journal of Thermal Analysis and Calorimetry - This study presents determining performance parameters as well as thermodynamic analysis through certain design parameters of a two-spool turbojet... 相似文献
5.
The synthesis of chiral liquid crystalline diacrylates is described. By mixing one of them with non-chiral liquid crystalline diacrylates. cholesteric phases are obtained of which the wavelength of reflection can be chosen by the composition of the mixture. After isothermal photopolymerization of the mixture a crosslinked network is obtained with thermally stable properties. 相似文献
6.
Christian Hammer Benjamin Walther Hikmet Karabulut Manuel M. Lohrengel 《Journal of Solid State Electrochemistry》2011,15(9):1885-1891
Anodic Ta oxide films are said to inhibit oxygen evolution. In industry, however, large amounts of gas are evolved during
the anodization of tantalum anodes for electrolytic capacitor fabrication. We quantified the oxygen by fluorescence quenching
in a flow-through cuvette and found that 4% of the anodic charge are consumed for oxygen evolution. In wires or sheets, this
oxygen is removed by diffusion without bubble formation and, thus, not recognized. Due to the large inner area of the sintered
Ta anodes, the oxygen evolution causes strong oscillations of the current density and bubble formation. The amount of oxygen
is proportional to the oxide amount formed in parallel. This is explained by a model where mobile ions during oxide growth
form interband states which allow electron tunneling. Accordingly, stationary no oxygen evolution is observed. 相似文献
7.
Liquid crystal (LC) mixtures of a reactive diacrylate and a commercial ferroelectric liquid crystal (FLC) mixture were produced. The mixtures were brought into cells provided with orientation layers in which various orientations such as uniaxial and twisted orientations, could be induced. When the desired orientation had been obtained, the polymerization of the reactive molecules was induced creating a three-dimensional anisotropic network containing the FLC molecules which were not chemically attached to the network (ferroelectric gels). The presence of the anisotropic network was found to have a large effect on various properties of the FLC molecules. For example, complex orientations (for example, 180° twisted) obtained by polymerization (formation of the gel) in the nematic phase remained unchanged when the gel was cooled to the FLC phase. Likewise uniaxial orientation, which cannot be realised in thick cells containing the pure FLC, could be realised when ferroelectric gels were used. For this reason the ferroelectric gels will be referred to as an anisotropic network-stabilized FLC. Optical properties such as effective birefringence and tilt angle were also influenced by the network. When use was made of a network with a lower birefringence than the FLC, a reduced effective birefringence in gels was observed. This is important for technologies involving thicker cells. The switching covered a range of voltages in the case of the gels, instead of showing a well-defined threshold voltage as in the bulk. The possibility of using this effect to obtain grey scales in cells during passive addressing has also been demonstrated. 相似文献
8.
The antibacterial activity of honey samples from different sources were collected and investigated against Bacillus cereus, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 27736, Morganella morganii, Micrococcus luteus NRRL B-4375, Escherichia coli ATCC 35218, and Candida albicans. Pathogens exhibited different sensitivities towards the honey samples. The results showed that majority of the honey samples (75%) generally inhibitied the bacteria tested. The honey samples which were obtained from Izmir (samples 1 and 2) proved more effective as inhibitors against P. aeruginosa, E. coli, and S. aureus. The honey which was obtained from Mu?la (sample 5) exhibited high anticandidal activity on C. albicans. A comparison of the honey samples on the basis of pollen content revealed that they were heterofloral, and samples which had highest antibacterial activity against P. aeruginosa, E. coli, and S. aureus were dominated by pollen from Chenopodiaceae/Amaranthaceae (sample 1), and Trifolium, Trigonella, Cyperaceae, Zea mays and Anthemis taxa (sample 2). The honey proved more effective on bacteria than antibiotics. 相似文献
9.
Single and dual substituent correlation analysis were applied to study transmission of substituent effects on IR carbonyl and thiocarbonyl stretching frequencies of 4-substituted phenyl-4,5-dihydrobenzo [f] [1,4] oxazepin-3 (2H)-ones (5a–n) and -thiones (6a–n). The substituent effects were estimated on the basis of results of the statistical analysis. The differences among the regression coefficients were discussed in terms of the relative importance of the substituent field and resonance effects. For a better understanding of the results, density functional theory (DFT) calculations were performed to determine the preferred geometry and to calculate the theoretical carbonyl and thiocarbonyl stretching frequencies. 相似文献
10.
Hikmet Aĝirbaş Selahattin Güner 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):257-263
Abstract 4-Substituted-2,3-1H-benzoxazine-1-thiones were prepared by the treatment of the corresponding benzoxazine-1-ones with P2S5. The thermal rearrangement of 4-substituted-2.3-1H-benzoxazine-1-thiones, catalysed by metallic copper, yielded 4-substituted-2.3-1 H-benzthiazine-1-ones. 相似文献