 | Phase Behavior of PLCs |  |
Polymer liquid crystals will most certainly become more important as research into this field progresses. Applications for these materials range from the production of high-strength materials to their use in optical devices. The following is an introduction to some of these applications.
An application of polymer liquid crystals that has been successfully developed for industry is the area of high strength fibers. Kevlar, which is used to make such things as helmets and bullet-proof vests, is just one example of the use of polymer liquid crystals in applications calling for strong, light weight materials.
Ordinary polymers have never been able to demonstrate the stiffness necessary to compete against traditional materials like steel. It has been observed that polymers with long straight chains are significantly stronger than their tangled counterparts. Main chain liquid crystal polymers are well-suited to ordering processes. For example, the polymer can be oriented in the desired liquid crystal phase and then quenched to create a highly ordered, strong solid. As these technologies continue to develop, an increasing variety of new materials with strong and light-weight properties will become available.
The use of polymer liquid crystals in the display industry is an exciting area of research. At this time, PLC's demonstrate relatively slow "response times" to electric fields. That is, when a field is applied, the molecules take a long time to align along it. This is not a good property for use in displays where the screen must be able to change rapidly from one view to another. Researchers are working to overcome this problem because the manipulation of polymers is often much easier than traditional liquid crystals.
In applications for which response time is not a factor (or in the future, after response times have improved), a twisted nematic polymer liquid crystal cell can be used to make energy efficient displays. A laser is used to selectively melt portions of the display into the liquid crystal phase. The orientation of the cell is then chosen by applying a field across it, just as in an ordinary twisted nematic liquid crystal cell. When the polymer cools down and hardens into a glass, the mesogens will be locked in that configuration and the field can be turned off.
Side chain polymer liquid crystals exhibit good properties for applications in optically nonlinear devices including optical waveguides and electro-optic modulators in poled polymeric slab waveguides. More devices are expected to be fabricated from PLCs in the future: optically-addressed spatial light modulators, tunable notch filters, optical amplifiers, and laser beam deflectors. The properties of ferroelectric chiral smectic C phases make this material useful for films with applications in nonlinear optics.
| | Phase Behavior of PLCs | |