|Ansprechpartner: Reiner Giesa, Hans-Werner Schmidt, Peter Strohriegl|
Cholesteric liquid crystals have attracted special interest as result of their selective reflection of light which is caused by the helical structure of the cholesteric mesophase.
Cholesteric mesophases can be obtained by mixing a nematic host with small amounts of a chiral dopant. The reflected wavelength depends on the viewing angle, with increasing viewing angle a blueshift can be observed. This effect, called color flop, is the origin for the increasing interest in this class of materials.
Anisotropic, permanently fixed cholesteric
networks find various applications e. g. as holographic writing or data
recording materials, polarizers, screen printing inks (Ultraking®
Paliocolor® by BASF AG), and can be further processed into pigment
particles for car paints. These organic color flop pigments are
distinguished from inorganic pigments by a high contrast color flop and
excellent color brilliance.
|Schmitt, G.; Giesa, R.; Schmidt, H.-W.: Cholesteric networks based on lyotropic mixtures, ChemPhysChem, 4, 505-508 (2003)|
|Pfeuffer, T.; Hanft, D.; Strohriegl, P.: Vitryfying star-shaped liquid crystals: synthesis and application in cholesteric polymer networks, Liquid Crystals 29, 1555-1564 (2002)|
|Pfeuffer, T.; Strohriegl, P.; Theissen, U.; Zilker, S.J.: Vitrifying cholesteric materials with photopolymerizable groups synthesis and holographic applications, Proceedings of SPIE 4463, 40 (2001)|
|Schmitt, G.; Schmidt, H.-W.; Giesa, R.: New liquid crystalline di- and tetra-acrylates for network formation, Liquid Crystals 28, 1611-1621 (2001)|
|Theissen, U.; Zilker, S.J.; Pfeuffer, T.; Strohriegl, P.: Photopolymerizable Cholesteric Liquid Crystals New Materials for Holographic Applications, Advanced Materials, 22, 1698 (2000)|
|Schmitt, G.; Giesa, R.; Schmidt, H.-W.: New nematic diacrylates with a calamitic core of four to six aromatic rings for the preparation of cholesteric networks, Freiburger Arbeitstagung Flüssigkristalle 29, 10 (2000)|
|Kürschner, K.; Strohriegl, P.: Polymerizable Liquid Crystalline Twin Molecules, Synthesis and Thermotropic Properties, Liquid Crystals 27, 1595 (2000)|
|Pfeuffer, T.; Kürschner, K.; Strohriegl, P.: Novel nematic bis-1,5-hexadiene monomers: Synthesis and photopolymerization to cholesteric polymer networks, Macromolecular Chemistry and Physics, 200, 2480 (1999)|
|Stohr, A.; Strohriegl, P.: Polymer networks containing cholesteryl compounds of different functionality, Pure & Applied Chemistry, A 34, 1125 (1997)|
|Stohr, A.; Strohriegl, P.: Synthesis and optical characterization of cholesteric polymer networks, Molecular Crystals Liquid Crystals, 299, 211 (1997)|