共查询到5条相似文献,搜索用时 0 毫秒
1.
Naohiro Terasawa Nobutaka Tanigaki Kenji Kiyohara 《Journal of fluorine chemistry》2006,127(8):1096-1104
The alignment behavior of the triphenylene compounds possessing fluoroalkylated side chains was investigated for the hexagonal columnar (Colh) mesophase on the polyimide-, cetyltrimethylammonium bromide (CTAB)-, and indium-SnO2 (ITO)-coated glass substrates by polarizing optical microscopy. It was found that 2,3,6,7,10,11-hexakis(1H,1H,2H,2H,3H,3H-perfluoroheptyloxy)- and 2,3,6,7,10,11-hexakis(1H,1H,2H,2H,3H,3H-perfluorononyloxy)-triphenylenes exhibit a spontaneous homeotropic alignment on these substrates, in contrast to the non-uniformity of alignment of Colh phase in the corresponding hydrocarbon mesogens. On the other hand, it was also found that 4,4,4-trifluorobutyloxy, 4,4,5,5,5-pentafluoropentyloxy and 4,4,5,5,6,6,6-heptafluorohexyloxy derivatives do not show such a spontaneous homeotropic alignment on these substrates. These results indicate that the spontaneous homeotropic alignment of the Colh phase could be easily attained by the introduction of an appropriate number and length of the fluoromethylene chains in the peripheral parts of discogens. 相似文献
2.
Jinsoo Kim Young Ju Jung Jae-Won Ka Eun Chol Kim Taek Ahn Mi Hye Yi 《Liquid crystals》2013,40(12):1451-1457
This report discusses the preparation and the unusual mesomorphism of three homologues of photopolymerisable triphenylene ether compounds. These homologues showed ‘a cold crystallisation’ on heating differential scanning calorimetry curves, and this phenomenon is attenuated with increase methylene units, spacers between the triphenylene core and the terminal photopolymerisable acrylate group. Classical textures of hexagonal columnar (Colh) mesophase were observed by polarising optical microscopy for all three photopolymerisable mesophase compounds described here. Also described is the mesomorphism of their intermediates, hydroxylalkoxytriphenylenes. In some cases, the discotic columnar hexagonal mesophases were confirmed by wide angle X-ray scattering techniques. 相似文献
3.
Thorsten Geisler Karin Popa Rudy J.M. Konings 《Journal of solid state chemistry》2006,179(5):1490-1496
We have studied the structural evolution of monoclinic BaZr(PO4)2 during heating up to 835 K by Raman spectroscopy. In agreement with previous studies we found a first-order phase transition at about 730 K during heating while upon cooling the reverse transition occurs at 705 K. However, some disagreement about the crystal structure of the high-temperature polymorph occurs in the literature. While the space group has not yet been determined, the X-ray diffraction pattern of the high-temperature phase has been indexed on either an orthorhombic or a hexagonal unit cell. We found that the number of Raman active internal PO4 vibrational modes decrease from nine to six during the transition. A group theoretical survey through all orthorhombic, trigonal, and hexagonal factor groups revealed that the observed number of vibrations would only be consistent with the Ba and Zr atoms located at a site, the P and two O atoms at a C3v(3m), and six O atoms at a Cs(m) site in the D3d factor group. Based on our Raman data, the space group of the high-temperature polymorph is thus either , , or . 相似文献
4.
A series of double-chain sulfobetain zwitterionic surfactants with varying carbon number of the intercharge group (spacer), (C16H33)2NCH3(CH2)nSO3, where n=2, 3, 4, and 6, referred to as (C16)2NCnS, were synthesized. The influence of the spacer length on the thermal behaviors of (C16)2NCnS in their pure state was studied using thermogravimetry (TG), differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) showed that the thermal stability of (C16)2NCnS lowered with increasing the spacer length. All compounds showed a complex polymorphism. Only for (C16)2NC4S and (C16)2NC6S, thermotropic liquid crystals were observed using POM. The former exhibited a smectic A (SmA) phase, whereas the latter formed a hexagonal columnar phase. These liquid crystals obtained both in the cooling and the second heating scans provided compelling evidence for the thermal stability of these compounds. 相似文献