Dingqian Shi,Kun Hu,Pei Chen,Weisong Du,Aiai Gao,Ran Chen,Xinbing Chen,Zhongwei An
A series of nematic heterocyclic liquid crystals, 2-(2ʹ-fluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(2)PBx) bearing hydrogen (nPF(2)PBH), methyl (nPF(2)PBM) and nitro (nPF(2)PBN) terminal groups, respectively, are developped and investigated. The results show that the nematic mesophase stability is obviously improved via a slightly increase in the inter-ring twist angle between the planes of two phenyl rings in the biphenyl unit, where modification of the twist angle can be achieved by adjusting the position of the lateral monofluorine substituent from the outer to the inter ring of the biphenyl mesogenic core unit. Meanwhile, the inter-ring lateral fluorine substituent results in a decrease in both melting and clearing points but only a nematic mesophase with an acceptably wide mesophase range for nPF(2)PBx, and thus a potential application in liquid crystal display mixtures is expected, especially for the compounds nPF(2)PBM and nPF(2)PBN. The reduced π–π interaction/conjugation caused by the increased twist angle is considered as one of the possible reasons for the formation of a nematic mesophase.
Qiang Weng,Longyan Duan,Pei Chen,Aiai Gao,Xinbing Chen,Zhongwei An
Modifying the position and numbers of lateral fluorine substituent is a common method to design and adjust the mesophase of liquid crystal compounds. Here, a series of 2-(2,2ʹ-difluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-5-substituted benzoxazole with both non-polar (H, CH3) and polar (NO2) groups (coded as nPF(2)PF(2)Bx) is synthesised and characterised. All of the compounds show a conspicuous inter-ring twist angle of 38° compared with corresponding reference compounds I and II which are calculated by density functional theory method, and it is interesting to note that the final compounds nPF(2)PF(2)Bx show only nematic mesophase during heating or cooling. Meanwhile, the UV-vis absorption bands and photoluminescence emission peaks both display remarkable blue-shifted. The aforementioned results reveal that lateral difluoro substituents play a key role to stable the nematic mesophase by increasing the dihedral angle of biphenyl.
Gang Zhang,Shu-shan Yuan,Zhi-min Li,Sheng-ru Long,Jie Yang
Two kinds of high glass temperature poly(arylene ether sulfone)s containing thioether and biphenyl units (PASSs) have been developed. The polymers were prepared by a polycondensation reaction of 4,4′-bis(4-chlorophenylsulfone)biphenyl (BCPSB) and 4,4′-dimercaptodiphenyl sulfone (DMDPS) (or 4,4′-bis(4-mercaptophenylsulfone)biphenyl (BMPSB)). They showed good thermal properties such as a relatively high glass transition temperature of 263–282 °C and a 5% weight-loss temperature (T5%) of 441–445 °C. The water flux and retention rate of the resultant membranes were 0.61–2.48 L m−2 h−1 and 89.47–94.91%, respectively. Interestingly, we found that the corrosion resistance of the membranes had been largely improved with the oxidization treatment. They were even insoluble in NMP, DMSO, concentrated H2SO4, aqua regia and so on, while the polymers without oxidation were soluble or destroyed in above solvents. In addition, we found the water flux of the oxidized membrane was also improved but the retention rate only decreased a little.
危险品化学品经营许可证（带存储）