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Development of New Azobenzene Photo-Alignment Molecules on Controlling the Tilt Angle of Liquid Crystals

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[Technical Report, Final Report]

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Cholesteric liquid crystals CLCs have been of great interest due to their selective reflection of light maximum reflection 50 and can be used as optical fibers, light shutters, smart windows and displays. Previously, dynamic electro-optic responses of polymer stabilized CLCsPSCLCs have been reported, including red or blue shifting tuning, bandwidth broadening, and switching response. Compared to the normal angle of incidence, a single PSCLC cell exposed to a large angle of incidence 50 degree exhibits very low transmittance high optical density in the reflection band 99 reflection and high out-of-band transmission. However, in order to be used an optical device requiring high optical density, a large prism having an angle of 60 degree or more must be used, which is a big hurdle to overcome. Instead of using a prism, an alternative approach is to tilt the helical axis of CLC across the cell thickness. In this project, light-responsive azobenzene functionalized POSS derivatives are designed and synthesized as new photo-alignment materials. By controlling the orientation of the light-responsive POSS molecules in the LC medium, the tilt angle of the LC and the helical axis of the CLC can be adjusted. The goal of this work is to control the angle of the helical axis of the CLC in the cell by exposure to linearly polarized blue light. The reflection efficiency optical density increases as the helical axis of the CLC tilts towards the cell surface. A single PSCLC sample with a tilted CLC helical axis 50 degree will provide excellent optical density and high out-of-band transmission.

Subject Categories:

  • Physical Chemistry
  • Electrooptical and Optoelectronic Devices

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[A, Approved For Public Release]