Liquid crystalline polymers ferroelectric properties

S. and K. tmura. Liquid crystalline arid ferroelectric properties of tartrate with two chiral centers, Chem Lea, 2217 (1969) Thermal and ferroelectric properties of dural liquid crystalline potytartralc, Chem Lea, 1031 (1990) Ferroelectric liquid rystalline po-lytartrate. Polymer J. 23 1483 (1991). 

M. Doi, Rheological properties of rodlike polymers in isotropic and liquid crystalline phases, Ferroelectrics, 30, 247 (1980). 

Ujiie, S., and limura, K., Phase transitions and ferroeleetrie properties of liquid crystalline polymer having a chiral tartrate unit, Ferroelectrics, 148, 263-269 (1993). 

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. 

In semicrystalline dipole electrets, polar crystallites are present in addition to the polar amorphous phase (Fig. 2b). In die technically most interesting semicrystalline dipole electrets such as polyvinyhdene fluoride (PVDF) and its copolymers with trifluoro ethylene (P(VDF-TrFE)) (Lovinger 1983) or hexafluoropropylene (P(VDF-HFP)), odd Nylons 7 and 11, polyureas, polyureflianes (PU), and some liquid crystalline polymers, the crystallites are ferroelectric (Vasudevan et al. 1979 Hattori et al. 1996). The terpolymer poly(vinyhdene-fluoride-trifluoroethylene— chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) has been shown to have relaxor ferroelectric properties as the CTFE group destabilizes die long-range order of the ferroelectric phase (Xu et al. 2001). 

Application of the concepts obtained in the study of PVDF and its copolymers has been made for other types of novel polymers with similar polar chemical structure. For example, poly(vinylidene cyanide) (PVDCN) and its copolymer with vinyl n-fatty acid ester have ciMmical structures close to that of PVDF F atoms arc displaced by CN groups. These polymers are also attracting attention because of their characteristic electric properties. Odd-numbered members of nylon (nylon 7, nylon 11, etc.) and ferroelectric liquid-crystalline polymers (FLCP) are also the candidates for ferroelectric polymers. These substances are still new. and their structural study has not yet been developed extensively compared with the study of PVDF and its copolymers. 

Ferroelectric Liquid Crystalline Polymers Properties and Applications... 

The author s group chose polyacrylate [102, 103], polyoxyethylene [104, 105], polysiloxane [103], and a polyacrylate/polysiloxane hybrid polymer [106] as the main chain according to the design in Fig. 1.26b-e. We attached various kinds of side-chain structures onto polymer main chains described above and checked the physical properties of these side-chain-type ferroelectric liquid crystalline polymers (FLCPs). 

To produce novel LC phase behavior and properties, a variety of polymer/LC composites have been developed. These include systems which employ liquid crystal polymers (5), phase separation of LC droplets in polymer dispersed liquid crystals (PDLCs) (4), incorporating both nematic (5,6) and ferroelectric liquid crystals (6-10). Polymer/LC gels have also been studied which are formed by the polymerization of small amounts of monomer solutes in a liquid crystalline solvent (11). The polymer/LC gel systems are of particular interest, rendering bistable chiral nematic devices (12) and polymer stabilized ferroelectric liquid crystals (PSFLCs) (1,13), which combine fast electro-optic response (14) with the increased mechanical stabilization imparted by the polymer (75). 

It can be safely predicted that applications of liquid crystals will expand in the future to more and more sophisticated areas of electronics. Potential applications of ferroelectric liquid crystals (e.g. fast shutters, complex multiplexed displays) are particularly exciting. The only LC that can show ferroelectric property is the chiral smectic C. Viable ferroelectric displays have however not yet materialized. Antifer-roelectric phases may also have good potential in display applications. Supertwisted nematic displays of twist artgles of around 240° and materials with low viscosity which respond relatively fast, have found considerable application. Another development is the polymer dispersed liquid crystal display in which small nematic droplets ( 2 gm in diameter) are formed in a polymer matrix. Liquid crystalline elastomers with novel physical properties would have many applications. 

Recently, liquid-crystalline polyphenylene derivatives have been synthesized through substitution of a fluorine-containing chiral liquid-crystalline group into side chains, with an aim to develop ferroelectric liquid-crystalline conjugated polymers (Fig. 5 Suda and Akagi 2008). These are attracting interest because they can afford anisotropies in electrical and optical properties when they are macroscopically aligned. This study also elucidated that PPP can be used to prepare new types of polymer materials. 

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... 

H. Goto, X. Dai, T. Ueoka, K. Akagi, Synthesis and properties of polymers from monosubstituted acetylene derivatives bearing ferroelectric liquid crystalline groups, Macromolecules, 37, 4783-4793 (2004). 

Svensson, M., Helgee, B., Skarp, K., Hermann, D., and Andersson, G., Chiral liquid crystalline side-chain polymers effects of side-chain length on physical properties, Ferroelectrics, 181, 319-326 (1996). 

Pfeiffer, M., Beresnev, L. A., Haase, W., Scherowsky, G., Kuehnpast, K., and Jung-bauer, D., Dielectric and electrooptic properties of a switchable ferroelectric liquid crystalline side chain polymer. Mol. Cryst. Liq. Cryst., 214, 125-141 (1992). 

This book was conceived as a renewed version of the earlier published original book, Electro-Optical and Magneto-Optical Properties of Liquid Crystals (Wiley, Chichester, 1983) written by one of us (L.M. Blinov). That book was first published in Russian (Nauka, Moscow, 1978) and then was modified slightly for the English translation. Since then new information on electrooptical effects in liquid crystals has been published. Novel effects have been discovered in nematics and cholesterics (such as the supertwist effect), and new classes of liquid crystalline materials, such as ferroelectric liquid crystals, appear. Recently, polymer liquid crystals attracted much attention and new electrooptical effects, both in pure polymer mesophases and polymer dispersed liquid crystals, were studied. An important contribution was also made in the understanding of surface properties and related phenomena (surface anchoring and bistability, flexoelectricity, etc.). 

M. PCeilfar, L. A. Bresncv. W. Haase, O. Scberawald, K. Kflhnpaai. and K. Jungbauer, Dielectric and electro-optic properties of a sariicbable ferroelectric liquid crystalline side-diain polymer. MoL Cryst fiq. Crysi 214 125 (1992). 

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