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Department Chemie
Prof. Dr. rer. nat. Heinz-Siegfried Kitzerow
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Electro-optics of polymer composites and nanoparticle dispersions

Combining the anisotropic optical properties of liquid crystals (LCs) with the mechanical properties of polymers has a large potential for possible applications. Flexible displays, optical polarizing or compensating filters, switchable holograms and optical storage are just a few examples of emerging technologies. Currently, we are working on polymer-stabilized blue phases, which are promising materials for a new generation of liquid crystal displays (LCDs). They exhibit fast switching, high contrast and easy fabrication. The benefits of the underlying optical Kerr effect have been known for a long time, but only the combination with a polymer network enabled enhancing the temperature range of the appearance of LC blue phases to values that are technically needed.

Light scattering setup for basic investigations on blue phases [Dr. Jürgen Schmidtke]

Dispersion of nanoparticles in ordered fluids can also alter and hopefully enhance the electro-optic performance of LCs, considerably. Our studies include the dispersion of metal-, luminescent semiconductor-, dielectric and ferroelectric particles in LCs. Confocal microscopy, X-ray diffraction and electro-optic studies indicate that nanoparticles can alter the alignment, the order parameter and the electro-optic switching behaviour. The switching from a bright ground state to a field- induced dark state can even be inverted (dark ground state, field-induced bright state) by adding nanoparticles to a LC.

Electroconvection pattern observed in a nanoparticle-doped liquid crystal (bar: 100 μm) [Dr. Martin Urbanski]

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