Liquid Crystals
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| A free-standing liquid crystal film taken in the smectic ferri-1 phase. |
| photo by C. C. Huang group |
The search for new methods of processing and displaying information has emphasized the importance of development and characterization of novel electro-optic materials. For example, creating faster optical switches requires a better understanding of high-polarization materials that allow controllable switching between different optical states. One such group of materials is liquid crystals. These materials have long been used in display technology (LCDs), which has advanced significantly with the synthesis of high-polarization liquid-crystal compounds. In the future, these materials may fill even greater needs for high speed switching in fiber optic applications.
In addition to their technological importance, liquid crystals are fundamentally interesting. Some high-polarization liquid crystals have a rich phase sequence consisting of six or more phases in a fairly narrow temperature window. Such compounds provide a unique set of systems for studying structural and orientational molecular ordering.
In recent years, Prof. C. C. Huang and his group have studied free-standing films of liquid crystals, which resemble soap bubbles on a ring. The films can range in thickness from two to several thousand molecular layers. The well-aligned substrate-free films provide an excellent sample in which to study liquid-crystal ordering. To study the films they use various optical probes, including ellipsometry, differential optical reflectivity, and depolarized reflected light microscopy. The acquired data, combined with computer modeling, allow them to investigate the molecular arrangements within the films. In recent years, the group has determined the interlayer structures of three chiral smectic phases. They also theoretically predicted the existence of a new phase that was subsequently confirmed experimentally. The group has also been involved in the development of the state-of-the-art method of resonant x-ray scattering. This synchrotron-based research has contributed to the advancement of orientational crystallography techniques.
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