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Articles by Li Niu
Total Records ( 2 ) for Li Niu
  Qixian Zhang , Liansheng Jiao , Changsheng Shan , Peng Hou , Bin Chen , Xiaoyu Xu and Li Niu
  A novel series of compounds with different counter anions, i.e. 1-lcub[4-(4-nitrophenylazo)phenyloxy]rcubalkyl-3-methyl-1H-imidazol-3-ium bromide salts (Cn , n = 3, 6, 10) and tetrafluoroborate salts (Dn , n = 3, 6, 10), were synthesised by the incorporation of an imidazolium group into paraffin side chain-terminated 4-nitroazobenzene derivatives. Their chemical structures were determined by 1H NMR, 13C NMR, UV spectroscopy and elemental analysis. The thermotropic liquid crystalline properties of these materials were further studied by polarising optical microscopy, wide-angle X-ray diffraction and differential scanning calorimetry. The results show that Cn and Dn (n = 6, 10) exhibit smectic liquid crystalline phases. The ionic liquid groups play an important role in forming the smectic layer structure, via enhancement of the thermal stability of the smectic state.
  Qixian Zhang , Changsheng Shan , Xiaodan Wang , Lili Chen , Li Niu and Bin Chen
  Imidazolium-substituted azobenzene liquid crystal derivatives were synthesised and their chemical structures were determined by 1H NMR, 13C NMR and UV spectroscopy and elemental analysis. The liquid crystalline properties pf the new compounds were investigated by differential scanning calorimetry, polarising optical microscopy and powder X-ray diffraction. The monomer DC10 was found to exhibit a monolayer smectic C (SmC) phase with schlieren texture on both heating and cooling. The effects of ionic interactions as well as the length of the alkyl chains on the mesophase are discussed. The results indicate that ionic interactions between imidazolium groups are the driving force for the formation of the monolayer SmC phase, the thermal stability of which is enhanced.
 
 
 
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