Ferro-electric liquid crystal

S)-2,3-chloro- 1-propanol (/ )-2,3-dlchloro-1 -propanol 100% ee Cl yf OH H Cl (5)-2.3-dichloro-1-propanol 100% ee base New materials, such as chiral polymers, ferro-electric liquid crystals, etc. 

Ikeda T, Sasaki T, Ichimura K. 1993. Photochemical switching of polarization in ferro electric liquid crystal films. Nature 361 428 430. 

Apart from these nCB examples, there have also been reports of STM images of ferro-electric liquid crystals on graphite surfaces [19-21]. The interesting conclusion from these results, in particular from those of [21], is that the enchanced tunneling efficiency of the benzene rings cannot simply be explained via the highest occupied or lowest unoccupied molecular orbitals. 

D. J. Byron, L. Komitov, A. S. Matham, I. McSherry, R. C. Wilson, The synthesis and characterization of a novel thiophene-based liquid crystal exhibiting ferro-, ferri- and antiferro-electric phase types, J. Mater. Chem., 6, 1871-1878 (1996). 

Rg. r.5 -If Number of ferroelectric substances known at the end of each year. The solid line represents aU ferro-electrics, including hqnid crystals and polymers. For liquid crystals and polymers, each gronp of homolognes is connted as one substance. The dashed line represents ferroelectric hquid crystals and polymers alone. Figure prepared by Prof. K. Deguchi... 

The existence or nonexistence of mirror symmetry plays an important role in nature. The lack of mirror symmetry, called chirality, can be found in systems of all length scales, from elementary particles to macroscopic systems. Due to the collective behavior of the molecules in liquid crystals, molecular chirality has a particularly remarkable influence on the macroscopic physical properties of these systems. Probably, even the flrst observations of thermotropic liquid crystals by Planer (1861) and Reinitzer (1888) were due to the conspicuous selective reflection of the helical structure that occurs in chiral liquid crystals. Many physical properties of liquid crystals depend on chirality, e.g., certain linear and nonlinear optical properties, the occurrence of ferro-, ferri-, antiferro- and piezo-electric behavior, the electroclinic effect, and even the appearance of new phases. In addition, the majority of optical applications of liquid crystals is due to chiral structures, namely the ther-mochromic effect of cholesteric liquid crystals, the rotation of the plane of polarization in twisted nematic liquid crystal displays, and the ferroelectric and antiferroelectric switching of smectic liquid crystals. 

Soon after the initial discovery of ferro-electricity in chiral smectic LCs it was predicted that, if the helix of an SmC phase were suppressed by surface forces in very thin layers between two glass electrodes, then this would pin the molecules in their positions and allow switching between two energetically equivalent polarization directions, thereby giving rise to an electro-optic memory effect [22]. This is the basis of the electro-optic display device called the surface stabilized ferroelectric liquid crystal... 

It was recognized as early as 1981 [54] that in order to achieve the ferroelectric state, a chiral liquid crystal is necessary. Chirality puts two molecules in the ideal unit cell, and this allows new modes of fluctuations and also new forms of organisation which also give possible minima in the free energy [ structure ] function. An electric field can now take the liquid crystal into one of these alternative forms of molecular packing, some of which can have a net ferroelectric moment per unit cell and therefore an overall ferroelectric moment. Columnar pyrenes made recently by Bock and Helfrich [55] have saturation polarization of -llOnCcm" and switch from the anti- to the ferro-electric state on a time scale of = 10 s with switching fields -10 V tm . Similar behavior has been... 

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