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Articles by Huai Yang
Total Records ( 12 ) for Huai Yang
  Qiang Wei , Lin Shi , Hui Cao , Liping Wang , Huai Yang and Yangbin Wang
  Two series of symmetrical azine-type liquid crystals were synthesised and their chemical structures identified by FTIR, 1H NMR and elemental analysis. Their mesomorphic properties were investigated by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. The characteristic of these liquid crystals is that they have a high clearing point (most were higher than 320°C) and a broad thermal range in the mesophase. The end groups of the liquid crystals had an effect on their mesomorphic properties. The series with alkoxy end groups all exhibited both smectic A (SmA) and a nematic phase, whereas the series with alkyl end groups showed only nematic phase at their lower analogues and showed both SmA and nematic properties at their higher analogues.
  Xiaokang Ding , Ming Cao , Huijing Liu , Hui Cao , Wenbo Li and Huai Yang
  Polymer-dispersed liquid crystal (PDLC) films were prepared by dual UV and heat curing from UV- and heat-curable monomers. For PDLC films with a certain amount of the UV- and heat-curable monomers, the mesh size (the size of LC domains) of the polymer network could be adjusted by adjusting the relative content of the two types of monomers, enabling the electro-optical properties of the film to be optimised.
  Guohui Pan , Lilong Yu , Hongbin Zhang , Jinbao Guo , Renwei Guo , Hui Cao , Zhou Yang , Huai Yang and Siquan Zhu
  A photopolymerisable monomer/liquid crystal (LC)/chiral dopant/photoinitiator mixture with a smectic A (SmA*)-chiral nematic (N*) phase transition was prepared. After the SmA* phase was homeotropically oriented and then irradiated by ultraviolet light, a homeotropically oriented polymer network was formed in the SmA* phase and then a homeotropically oriented polymer network-stabilised liquid crystal (PSLC) film with a SmA*-N* phase transition was prepared. In the temperature range of the SmA* phase, the LC molecules were homeotropically oriented and the film exhibited a transparent state. However, in the temperature range of the N* phase, the film exhibited a strong light-scattering state owing to the fact that the LC molecules adopted a focal conic alignment affected by the homeotropically oriented polymer network. The strong light-scattering state of the N* phase could be changed into a transparent one when an electric field was applied. The focus of this study was on the effects of composition of the PSLC film on its thermo-optical and electro-optical properties.
  Wei Huang , Zhenyu Bian , Kexuan Li , Jiumei Xiao , Hui Cao and Huai Yang
  The preparation is reported of particles of photopolymerisable monomer/chiral dopant composites with a crystalline (Cr)-chiral nematic (N*) phase transition. By mixing particles with different pitches of the N* phase in the Cr phase and crosslinking the liquid crystal (LC) monomer molecules by photopolymerisation in the planarly oriented N* phase, an N*-LC composite film with a non-uniform pitch distribution was obtained. Experimental results show that the bandwidth of the reflection spectrum and the location of reflection band of the composite films can be controlled accurately by controlling the pitch lengths of the N* phase of the particles. Effects of polymerisation temperature and UV intensity on the non-uniform pitch distribution of N*-LC composite films were investigated.
  Jinbao Guo , Fang Liu , Fengjin Chen , Jie Wei and Huai Yang
  In this study, a single-layer polymer-stabilised liquid crystal (PSLC) film reflecting both right- and left-circularly polarised light has been developed by a wash-out/refill method. A polymer network/liquid crystals (LCs) composite, in which the polymer network had a certain helical structure, was prepared by photo polymerisation of the photo-polymerisable LC monomers (LCMs) in a LCM/LC/photoinitiator mixture. Then, the LC molecules were extracted from the composite film and cholesteric LCs (Ch-LCs) with the opposite helical structure were refilled into the film. The film was constructed by the polymer network with a certain helical structure and Ch-LCs with the opposite helical structure could reflect both right- and left-circularly polarised light simultaneously. The reflection intensity of the film is close to 100% when the pitch lengths of the two opposite helical structures are the same, which goes beyond the 50% reflectance limit of Ch-LCs. It was demonstrated that the memory effect of the polymer network is an important mechanism for the resulting film properties.
  Qingyong Meng , Hui Cao , Miki Kashima , Huijing Liu and Huai Yang
  Polymer-dispersed liquid crystal (PDLC) films were prepared from thermal polymerisation-induced phase separation in heat-curable monomers/nematic liquid crystal (LC) mixtures. For PDLCs with a certain amount of LCs, the microstructure and the refractive index of polymer networks could be influenced by the relative content of epoxy monomers, owing to their different chemical structures. The effect of these factors on the electro-optic properties of films was also investigated.
  Renwei Guo , Hui Cao , Chaoyong Yang , Xiaojuan Wu , Qingyong Meng , Tao Liu , Wanli He , Zihui Cheng and Huai Yang
  A bandwidth-controllable reflective gel has been investigated from photo- and thermally-induced processes. Due to the pitch of cholesteric liquid crystal (CLC) composite increasing as the temperature rises, the CLC with short pitch is frozen by UV-curing the polymer network at low temperature and the CLC with long pitch is fixed by heat curing the polymer network at high temperature. A non-uniform pitch distribution of CLCs forms in the gel when temperature becomes low. It is demonstrated that the memory effect of the polymer network is an important mechanism for the resulting gel.
  Hai quan Zhang , Wen ke Liu , An lei Qin , Fei fei Wang , Li cheng Zhao , Shuai Zhang , Ying Li and Huai Yang
  A novel series of chiral dopants synthesised from (S)-1, 2-propanediol and mesogenic carboxylic acids were characterised by Fourier transform infrared and 1H nuclear magnetic resonance, and their helical twisting properties were investigated by doping the chiral dopants into a nematic liquid crystal host (SLC-1717). The results showed that the values of the molecular twisting power β were significantly dependent on the nature of the terminal substituents, terminal alkyl length and numbers of chiral centres in the molecular structure. Compared to compounds with electron-with-drawing groups (-NO2, -F, -CF3), the chiral compounds with terminal alkyl chains exhibited a higher β.
  Miki Kashima , Hui Cao , Huijing Liu , Qingyong Meng , Ding Wang , Fasheng Li and Huai Yang
  Polymer-dispersed liquid crystal (PDLC) films were prepared by photochemical polymerisation from an ultraviolet-curable monomer/crosslinking agent/initiator/liquid crystal (LC) mixture. The influences of the chain length of crosslinking agents on the PDLC system have been studied. The microstructures of the PDLC films were strongly influenced by the chain length of the crosslinker, which in turn influences the electro-optic properties of PDLC films. It is proved that adjusting the chain length of the crosslinking agents and the LC content can produce PDLC films that have good electro-optic properties with a lower LC content.
  Xiaotao Yuana , Lipei Zhang and Huai Yang
  Chiral propane-1,2-di-(4-(4-heptylcyclohexyl)benzoate) (PPCB) and 1-phenylethane-1,2-di-(4-(4-heptylcyclohexyl) benzoate) (PEPB) were synthesised and used as chiral dopants to induce chiral nematic liquid crystals (N*-LCs). Since the helical twisting power of the former first decreased and then increased as a result of thermally induced inversion helicity sense, and those of the latter changed little with increasing temperature, the pitch lengths of the N*-LCs prepared from (N-LC)/PPCB/(R)-PEPB and N-LC/PPCB/(S)-PEPB mixtures decreased and increased with increasing temperature respectively. Then, based on these two kinds of N*-LCs, polymer stabilised liquid crystal films were obtained, in which the bandwidth of the selective reflection spectra increased with increasing temperature.
  Wang Hu , Haiyan Zhao , Liankun Shan , Li Song , Hui Cao , Zhou Yang , Zihui Cheng , Chunzhu Yan , Sijin Li , Huai Yang and Lin Guo
  A magnetite (Fe3O4) nanoparticle/chiral nematic liquid crystal (N*-LC) composite was prepared and filled into a planar treated cell. The Fe3O4 nanoparticles had been modified by oleic acid so that they could be better dispersed in the composite. When a magnetic field was scanned on the outer surface of the cell locally, Fe3O4 nanoparticles moved towards the inner surface of the cell correspondingly, and the black expected information was displayed. When the magnet was applied to the opposite outer surface, the information was erased. After polymer network walls were prepared in the composite, the resolution of the information displayed increased. Then, through the formation of hydrogen bonds between the nanoparticles and chiral pyridine compound (CPC) doped in the composite, the pitch length of the N*-LC could be adjusted by altering the intensity of the applied magnetic field. The composite doped with CPC could potentially be used as a material for a type of reflective colour paper with magnetically controllable characteristics.
  Lipei Zhang , Wanli He , Xiaotao Yuan , Wang Hu , Hui Cao , Huai Yang and Siquan Zhu
  A polymer-stabilised cholesteric liquid crystal (PSChLC) was fabricated by ultraviolet (UV) induced polymerisation of photopolymerisable acrylate monomers mixed in a cholesteric liquid crystal (ChLC). A polymer network with a concentration gradient, which was induced by UV light absorption of dye along the propagation direction, was formed. A hydrogen bond, arising between the polymer network with a concentration gradient containing carboxyl as proton donors and chiral dopant (CD) as proton acceptors, induced a pitch gradient in PSChLC and then, as a consequence, broadband reflection. The broadband reflection is associated with the concentration and the composition of photopolymerisable acrylate monomers, the concentration of CD and the polymerisation temperature. Examining the morphologies of the polymer network by scanning electron microscopy, the helix structure and pitch gradient were verified, confirming the pitch gradient of the PSChLC and revealing the essence of the formation of broadband reflection.
 
 
 
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