Fabrication Of Light-Driven Chiral Azo Switch And Properties Of Flexible Display

In this paper, a kind of novel light-driven chiral azo switches bearing both axially chiral binaphthyl center and single tetrahedrally chiral center with different configuration were designed and synthesized. The chiroptical properties in solution and molecular conformation of the chiral azo switches were demonstrated. Meanwhile we doped these switches to a nematic liquid crystal host to induce cholesteric phase and discussed the ability to phototune the reflection color. On this basis we utilized the above chiral azo switch to fabricate a color photo-addressed flexible liquid crystal display driven by light and hidden as well as fixed by application of an electric field and studied the controlling conditions and mechanisms.Firstly, we synthesized four chiral azo switches and characterized their structures. The chiroptical properties and photoisomerization of the switches were investigated using UV-Vis absorption and CD spectra. The results indicated that the introduction of a tetrahedrally chiral center don’t influence the UV-Vis absorption and CD spectra while the maximum absorption wavelength became widely and the CD spectra changed by the import of a biphenyl rigid long chain. Then we calculated the optimized geometries of trans and cis form of the switches by the Gaussian03calculations at the B3LYP/6-31G(d) level. We can see that the molecular geometry bent because the existence of the tetrahedrally chiral center while the biphenyl rigid long chain can maintain the rod-like molecular geometry.Furthermore, small amounts of chiral azo switches doped in the nematic liquid crystal induced a cholesteric phase and the ability to phototune the reflection color was discussed in detail. The results showed that import of tetrahedrally chiral center dramatically decreased the HTP of axially chiral azo switch, while rigid long core increased the HTP. It is worth noting here the cholesteric liquid crystal induced by the switch is capable of fast and reversible phototuning the reflection color over the entire visible spectrum.At last, this chiral azo switches were used in a color photo-addressed flexible liquid crystal display and the performance of the device was studied. The information recorded in the display through a photomask by light irradiation, the pattern would be hidden when applying a22V pulse and reappeared by applying a46V pulse. Moreover, the information would be recorded indefinitely by applying a30V pulse.