標題: | Non-conventional three-armed star-shaped mesogens based on 1,3,5-trisubstituted benzene with azobenzene moieties at the periphery: synthesis, and mesomorphic behaviour |
作者: | Ooi, Yew-Hong Yeap, Guan-Yeow Han, Chun-Chieh Lin, Hong-Cheu Shinomiya, Teruo Ito, Masato M. 材料科學與工程學系 Department of Materials Science and Engineering |
關鍵字: | azobenzene;synthesis;XRD;terminal substituent;star-shaped liquid crystals;spectroscopic techniques |
公開日期: | 3-七月-2014 |
摘要: | A series of new symmetrical trimeric star-shaped mesogens in which the molecular architecture composed of three 4-[(4-substituted-phenyl)diazenyl]phenoxy-6-bromohexane connected as the pheripheral units to 1,3,5-positions of the benzene core group have been synthesised and fully characterised by physical measurements and spectroscopic techniques (carbon, hydrogen and nitrogen microanalysis, Fourier transform-infrared spectroscopy and nuclear magnetic resonance: CHN, FT-IR and NMR). At one end of the para-position of the azobenzene fragment consists of different terminal substituents X=F, Cl, Br, I, C2H5 and OC2H5. The thermal behaviour and mesomorphic properties of the star-shaped compounds were investigated by means of differential scanning calorimetry, polarizing optical microscopy (POM) and X-ray diffraction analyses. Moreover, the liquid-crystalline properties of all the intermediates 4-[(4-substituted-phenyl)diazenyl]phenoxy-6-bromohexane were also evaluated. Whilst all the star-shaped compounds exhibit nematic and smectic A phases, the mesogens with chloro- and bromo-terminal substituents were found to show soft crystalline phase. The smectic phase and the possible molecular arrangement of the star-shaped molecule within the anisotropic region were further substantiated by the XRD. In addition to a low-angle sharp peak (reflecting the layered structure), a diffuse wide-angle peak indicating the liquid-like order within the smectic layer was recorded. A comparative study between the properties of the present azo mesogens and the earlier reported star-shaped mesogens from Schiff bases is also discussed. |
URI: | http://dx.doi.org/10.1080/02678292.2014.898341 http://hdl.handle.net/11536/24389 |
ISSN: | 0267-8292 |
DOI: | 10.1080/02678292.2014.898341 |
期刊: | LIQUID CRYSTALS |
Volume: | 41 |
Issue: | 7 |
起始頁: | 1017 |
結束頁: | 1033 |
顯示於類別: | 期刊論文 |