Nematic mesophase enhanced via lateral monofluorine substitution on benzoxazole-liquid crystals |
| |
| Authors: | Dingqian Shi Kun Hu Aiai Gao Weisong Du Ran Chen |
| |
| Institution: | 1. Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, Shaanxi Normal University, Xi’an, P R China;2. School of Materials Science and Engineering, Shaanxi Normal University, Xi’an, P R China;3. Center of Opto-electronic Materials, Xi’an Modern Chemistry Research Institute, Xi’an, P R China |
| |
| Abstract: | Fluorine is widely used as a lateral substituent to modify the physical properties of liquid crystals. Here, laterally monofluorinated compounds, 2-(4?-alkoxy-2-fluorobiphenyl-4-yl)-benzoxazole derivatives (nPPF(2)Bx) bearing different substituents (H, CH3, NO2, coded as nPPF(2)BH, nPPF(2)BM and nPPF(2)BN, respectively) at 5-position, were synthesised and characterised. It is interesting to note that these only display enantiotropic nematic mesophases with mesophase ranges of 12–28°C and 13–45°C on heating and cooling for nPPF(2)BH, 46–97°C and 62–120°C for nPPF(2)BM and 82–108°C and 87–113°C for nPPF(2)BN, which are very different from the corresponding monofluorine-substituted analogue (compounds I) with enantiotropic smectic or smectic/nematic mesophases. The enhanced nematic mesophase is attributed to the reduced π–π interaction/conjugation resulting from the twisted structure of the molecule caused by the introduction of a fluorine atom into the inter-ring of the biphenyl unit. These results suggest that modification of the monofluorine substituent position is an effective method to improve the nematic mesophase in benzoxazole-liquid crystals. |
| |
| Keywords: | Lateral monofluorine nematic mesophase benzoxazole-liquid crystals inter-ring twist angle |
|
|
