Electro-optic Applications of Liquid Crystalline Polymers

ELECTRO-OPTIC APPLICATIONS OF LIQUID CRYSTALLINE POLYMERS... 

Characterization of Liquid Crystalline Polymers for Electro-optic Applications... 

Meredith, G. R., Vandsen, J. G., and Williams, D. J., Charactmzation of liquid crystalline polymers for electro-optic applications, in Nonlinear Optical Properties cf Organic and Polymeric Materials (ACS Symp. Sen, 233), Williams, D. J., Ed., American Chemical Society, Washington, D.C., 1983, 109. 

This chapter provides an overview of current researches on liquid crystalline polymers (LCPs). Topics include syntheses of main-chain and side-chain LCFs, structured characterization of LCFs and LCP networks and rheology and processing. Applications of LCP/polymer blends as self-reinforced polymers and electro-optical meterials are also discussed. 

Various aspects of liquid crystallinity in flexible polymers with the mesogenic moiety in the side group are discussed in several articles. The focus here is on the liquid crystalline behavior in electric fields and possible applications of PLCs in electro-optical display and recording. The properties of a novel group of PLCs — liquid crystalline elastomers — obtained from mesogenic side group systems are also described. 

Suda K, Akagi K (2008) Electro-optical behavior of ferroelectric liquid crystalline polyphenylene derivatives. J Polym Sci A Polym Chem 46 3591-3610 Sun HY, Chen HX, Zheng MS (2005) Synthesis, properties and applications of the polyphenylene. HuaXue Tong Bao 7 515-521... 

Liquid crystals, polymers and liquid crystalline polymers are soft condensed matter systems of major technological and scientific interest. In liquid crystals the orientational order of the constituent molecules is associated with a reduced or absent translational order. This gives liquid crystalline systems a combination of fluidity (liquid-like properties) and anisotropic electro optic properties, similar to those of a crystal. Orientational order can be controlled easily by the application of external fields, leading to the spatial switching of bulk properties in response to external stimuli. This provides the basis for a wide range of technological applications, including displays, optical switches, adaptive optics for telescopes and many other electro-optical devices. 

The surface-stabilized ferroelectric liquid crystals in the smectic C (SmC ) phase are among the most interesting types of liquid-crystalline systems because of their potential applications in high-resolution flat panel displays and fast electro-optical devices [73-76]. Within this class of compounds, ferroelectric liquid-crystalline polymers (FLCPs) have gained theoretical and practical interest as systems which combine the properties of polymers and ferroelectric liquid crystals. This combination is achieved by attaching the ferroelectric mesogen to a main chain via a flexible spacer... 

Ferroelectric liquid crystals (FLC) have attracted attention because of their high speed response and memory effect (7-5). The characteristics of fast response and memory effect make them suitable in electro-optical device applications, such as display, light valve and memory devices. Ferroelectric side chain liquid crystalline polymers (FLCPs) exhibit desirable mechanical properties of polymers and electro-optical properties of low molecular weight FLC, which have been investigated extensively Corresponding author. 

The structures of extra-chain liquid crystalline polymers present applicative interest today for other reasons than those of intra-chain LCP. Coupling of the mesogene with basic chain caused a classical liquid crystal behavior. On the other hand, these structures exhibit characteristics of processability and a mechanical behavior similar with that of polymers, having the same sensitivity to various external sohcitations (electric and/or magnetic field) as simple mesogenes, which recommends the utilization of liquid crystaline polymers with extra-chain mesophase for electro-optic applications [29-32]. 

Electro-optic The liquid crystal plastics exhibit some of the properties of crystalline solids and still flow easily as liquids (Chapter 6). One group of these materials is based on low polymers with strong field interacting side chains. Using these materials, there has developed a field of electro-optic devices whose characteristics can be changed sharply by the application of an electric field. 

Side-chain LCPs are, in a way, more subtle than their main-chain counterparts because, thanks to the flexible spacers, the polymer main chain (called backbone) still retains many degrees of freedom. In fact, there is a true balance between the natural disorder of the backbones and the liquid-crystalline order of the rod-like moieties. For instance, in the SmA phase, it was recently demonstrated by SANS that the backbone performs a 2-dimensional random walk between the smectic layers [22]. Therefore, these materials have poor mechanical properties but display a rich variety of mesophases, even at room temperature. This makes them more suitable for applications in displays and electro-optic devices. 

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