Ferroelectric liquid crystals ferroelectricity

Takahashi, K., Ishibashi, S., and Yamamoto, F., Direction of mesogenic side chains and its effect on the properties of polymeric ferroelectric liquid crystals, Ferroelectrics, 181, 277-285 (1996). 

Eber, N., Bata, L., Scherowsky, G., and Schliwa, A., Linear electromechanical effect in a polymeric ferroelectric liquid crystal, Ferroelectrics, 122, 139-147 (1991). Kozlovsky, M. V., Darius, M., and Haa.se, W., Frustrated pha.se behaviour of a chiral side chain polymer, European Polymer Journal, (in press). 

Moritake, H.. Fuwa, Yo., Sagioka, K., Watanabe, T.. Ozaki, M., and Yoshino, K., Light scattering in polymeric ferroelectric liquid crystal, Ferroelectrics, 181, 397-318 (1996). 

Yasuda et al. performed dielectric relaxation measurements on metastable solid MBBA, using a parallel-plate capacitor. Glass plates with strips of transparent tin-oxide-conducting coating served as electrodes. The cell was mounted in a copper beryllium pressure vessel, pressurized with liquid isopentane. A similar setup was used for the study of ferroelectric liquid crystals. Ferroelectric liquid crystals have also been studied by Chandrasekhar and co-workers who used a sapphire cell setup in a high-pressure apparatus. The sample was sandwiched... 

Fujisawa T, Nishiyama I, Hatsusaka K, Takeuchi K, Takatsu H, Kobayashi S (2008) Field sequential full color LCDs using polymer-stabilized V-shaped ferroelectric liquid crystals. Ferroelectrics 364(l) 78-85... 

Fume H, Takahashi T, Kobayashi S, Yokoyama H (2002) Models of molecular alignment stmcture in polymer-stabilized ferroelectric liquid crystals. Jpn J Appl Phys 40(l) 7230-7233 Giepehnann F, Zugenmaier P (1995) Mean-field coefficients and the electroclinic effect of a ferroelectric hquid crystal. Phys Rev E 52(2) 1762-1772 Giepehnann F, Hermann A, ZugeranaiCT P (1997) Experimental determination of Landau-expansion coefficients in ferroelectric liquid crystals. Ferroelectrics 200 237-256 Guymon CA, Hoggan EN, Walba DM, Qark NA, Bowman CN (1995) Phase behaviour and electro-optic characteristics of a polymer stabilized ferroelectric liquid crystal. Liq Cryst 19 719-727... 

Hikmet RAM, Boots HMJ, Michielsen M (1995) Ferroelectric liquid crystal gels—network stabilized ferroelectric display. Liq Cryst 19 65-74 Inoue T, Higuchi N, Fume H (2008) The effect of pol5mer doping on the formation of helical stmcture in ferroelectric liquid crystals. Ferroelectrics 364 113-120 Jean YC (1990) Positron annihilation spectroscopy for chemical analysis a novel probe for microstmctural analysis of polymers. Microchem J 42 72-102 Jean YC, Nakanishi H, Hao LY, Sandreczki TC (1990) Anisotropy of free-volume hole dimensions in polymers probed by positron annihilation spectroscopy. Phys Rev B 42 9705-9708 Jean YC, Mallon PE, Schrader DM (2003) Principles and application of positron and positronium chemistry. World Scientific, Singapore... 

Suresh S, Chien LC (2003) Electro-optical properties of polymer-stabilized ferroelectric liquid crystal. Ferroelectrics 287 1-6... 

Tsuda H, Waki N, Furue H (2008) Response time of polymer-stabilized ferroelectric liquid crystals. Ferroelectrics 365 108-114... 

As witli tlie nematic phase, a chiral version of tlie smectic C phase has been observed and is denoted SniC. In tliis phase, tlie director rotates around tlie cone generated by tlie tilt angle [9,32]. This phase is helielectric, i.e. tlie spontaneous polarization induced by dipolar ordering (transverse to tlie molecular long axis) rotates around a helix. However, if tlie helix is unwound by external forces such as surface interactions, or electric fields or by compensating tlie pitch in a mixture, so tliat it becomes infinite, tlie phase becomes ferroelectric. This is tlie basis of ferroelectric liquid crystal displays (section C2.2.4.4). If tliere is an alternation in polarization direction between layers tlie phase can be ferrielectric or antiferroelectric. A smectic A phase foniied by chiral molecules is sometimes denoted SiiiA, altliough, due to the untilted symmetry of tlie phase, it is not itself chiral. This notation is strictly incorrect because tlie asterisk should be used to indicate the chirality of tlie phase and not tliat of tlie constituent molecules. 

Lagerwall S T 1998 Ferroelectric liquid crystals Handbook of Liquid Crystals Vol 2B. Low Molecular Weight Liquid Crystals II ed D Demus, J Goodby, G W Gray, H-W Speiss and V Vill (New York Wiley-VCH)... 

Ferroelectric Liquid Crystals Principles, Properties and Applications (PMade ph a Gordon and Breach)... 

Clark N A, Handschy M A and Lagerwall S T 1983 Ferroelectric liquid crystal electro-optics using the surface stabilized structure Molec. Cryst. Liq. Cryst. 94 213-34... 

K. A. Epstein and co-workers, "Fluorinated Ferroelectric Liquid Crystals Overview and Synthesis," Eleventh Winter Fluorine Conference, St. Petersburg, Fla., 1993. 

Five-membered sulfur-containing heterocycles are important synthetic intermediates and have found a variety of applications in medical, agricultural, and material chemistry. Looking for potential candidates for ferroelectric display applications. Seed s group investigated the preparation of liquid crystals... 

Other more exotic types of calamitic liquid crystal molecules include those having chiral components. This molecular modification leads to the formation of chiral nematic phases in which the director adopts a natural helical twist which may range from sub-micron to macroscopic length scales. Chirality coupled with smectic ordering may also lead to the formation of ferroelectric phases [20]. 

In the operation of ferroelectric liquid crystal devices, the applied electric field couples directly to the spontaneous polarisation Ps and response times depend on the magnitude E Ps. Depending on the electronic structure (magnitude and direction of the dipole moment as well as position and polarity of the chiral species) and ordering of the molecules P can vary over several orders of magnitude (3 to 1.2 x 10 ), giving response times in the range 1-100 ps. 

Omenat, A., Serrano, J.L., Sierra, T., Amabilino, D.B., Minguet, M., Ramos, E. and Veciana, J. (1999) Chiral linear isocyanide palladium(II) and gold(I) complexes as ferroelectric liquid crystals. Journal of Materials Chemistry, 9, 2301-2305. 

Liquid Crystal Displays (LCD). Liquid crystal displays, once limited to small devices such as calculators, are now displacing color CRT (cathode ray tube) displays in commercial quantities. The ability to fabricate these display devices at high quality and at low cost is partially due to the wider spread use of photopolymer-based materials. Photopolymer technology is being used for the alignment of liquid crystal (LC) elements (49), the orientation of ferroelectric materials (50), the synthesis of LC polymers (57) and the manufacture of color filters for liquid crystal display applications (52). 

Photopolymerization and Electrooptic Properties of Polymer Network/Ferroelectric Liquid-Crystal... 

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). 

The amorphous diacrylate monomers chosen for study were two commercially available monomers, p-phenylene diacrylate (PPDA) and 1,6-hexanediol diacrylate (HDDA) (Polysciences, Inc., Warrington, PA). The liquid crystalline diacrylate studied was 1,4-di-(4-(6-acryloyloxyhexyloxy)benzoyloxy)-2-methylbenzene (C6M) (13). Chemical structures of these monomers as well as pertinent physical and LC properties are given in Figure 1. All monomers were used without further purification. The ferroelectric liquid crystal mixture consisted of a 1 1 mixture of W7 and W82 (1) (Displaytech, Boulder, CO). This mixture exhibits isotropic (I), smectic A... 

The earliest approach to explain tubule formation was developed by de Gen-nes.168 He pointed out that, in a bilayer membrane of chiral molecules in the Lp/ phase, symmetry allows the material to have a net electric dipole moment in the bilayer plane, like a chiral smectic-C liquid crystal.169 In other words, the material is ferroelectric, with a spontaneous electrostatic polarization P per unit area in the bilayer plane, perpendicular to the axis of molecular tilt. (Note that this argument depends on the chirality of the molecules, but it does not depend on the chiral elastic properties of the membrane. For that reason, we discuss it in this section, rather than with the chiral elastic models in the following sections.)... 

It was quickly recognized that chirality would play an important role in discotic liquid crystals, not only for the possibility of creating cholesteric and ferroelectric liquid crystals but also as a tool for studying the self-assembly of these molecules as a whole, both in solution and in the solid state. However, initial studies revealed that expression of chirality in discotic liquid crystals was not as straightforward as for liquid crystals derived from calamitic molecules. More recently, with the increase in interest in self-assembly and molecular recognition, considerably more attention has been directed to the study of chiral discotics and their assemblies in solution. The objective of this chapter is... 

To understand how chirality is expressed, it is important to first describe the different thermotropic mesophase assemblies which can be formed by chiral discotics. Even though expression of chirality has been observed in thermotropic mesophases, the chiral expression occurs in a rather uncontrolled manner, and systems which are suitable for applications, for example, easily switchable columns/ferroelectric discotic liquid crystals, consequently have not yet been developed. Hence, the assembly of discotics in solution has received considerable attention. Supramolecular assemblies of discotic molecules in solution are still in their infancy and have not yet found commercial application, but they are of fundamental importance since they allow a detailed and focused investigation of the specific interactions that are required to express chirality at higher levels of organization. As such, the fundamental knowledge acquired from supramolecular assemblies in solution might formulate the design criteria for thermotropic chiral discotic mesophases and provide the necessary tools for the creation of functional systems. 

Along with the prediction and discovery of a macroscopic dipole in the SmC phase and the invention of ferroelectric liquid crystals in the SSFLC system, the discovery of antiferroelectric liquid crystals stands as a key milestone in chiral smectic LC science. Antiferroelectric switching (see below) was first reported for unichiral 4-[(l-methylheptyloxy)carbonyl]phenyl-4/-octyloxy-4-biphenyl carboxylate [MHPOBC, (3)],16 with structure and phase sequence... 

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