Ferroelectric liquid crystals influence

In the most simple chiral polar tilted smectics, ferroelectric liquid crystals, the flexoelectric phenomenon influences the structure of the SmC phase only quantitatively. It affects the elastic and chiral couplings and consequently slightly changes the transition temperature to the tilted phase and the pitch of the helicoidal modulation. 

Liquid crystals are birefringent and they therefore influence the state of polarization of light beams. This interaction is described by the Jones calculus [2], which is briefly outlined below, prior to using it to establish basic results in light modulation by ferroelectric liquid crystals. 

Archer P, Dierking I (2009) Electro-optic properties of polymer-stabilized ferroelectric liquid crystals before, during and after photo-polymerization. J Opt A Pure Appl Opt 11(2) 024022 Archer P, Dierking I, Osipov MA (2008) Landau model for polymer-stabilized ferroelectric liquid crystals experiment and theory. Phys Rev E 78(5) 051703 Bahr CH, Heppke G (1990) Influence of electric field on a first-order smectic-A-foroelectric-smectic-C liquid-crystal phase transition a field-induced critical point. Phys Rev A 41 (8) 4335 342... 

Detailed theory and experimental observation of laser-induced director axis reorientation in a chiral smectic-C (ferroelectric) liquid crystal were reported by Macdonald et al. This study was conducted with a surface-stabilized ferroelectric liquid crystal in a planar oriented bookshelf-like configuration, where the director axis of the molecules is parallel, and the smectic layer perpendicular, to the cell walls (Fig. 8.16). Typically, the induced reorientation angle by a laser of intensity on the order of3000 W/cm is about 23°, with a switching time measured to be on the order of a millisecond or less. At such high optical intensity, the authors also noticed strong influence from laser heating of the sample. 

The orientation of liquid crystals can be influenced by an electric field. This property makes LCPs attractive for LCDs. Some liquid crystals undergo a spontaneous electric polarization even in the absence of an external electric field. This phenomenon is referred to as a ferroelectricity. 

Perhaps one of the most important applications of chiral induction is in the area of liquid crystals. Upon addition of a wide range of appropriate chiral compounds, the achiral nematic, smectic C, and discotic phases are converted into the chiral cholesteric (or twisted nematic), the ferroelectric smectic C and the chiral discotic phases. As a first example, we take the induction of chirality in the columns of aromatic chromophores present in some liquid-crystalline polymers. " The polymers, achiral polyesters incorporating triphenylene moieties, display discotic mesophases, which upon doping with chiral electron acceptors based on tetranitro-9-fluorene, form chiral discotic phases in which the chirality is determined by the dopant. These conclusions were reached on the basis of CD spectra in which strong Cotton effects were observed. Interestingly, the chiral dopants were unable to dramatically influence the chiral winding of triphenylene polymers that already incorporated ste-reogenic centers. 

It has been known for a long time that the surface ordering of a nematic (or other non-polar) liquid crystal is influenced by the ferroelectric domains of the anchoring substrate. In a work by M. Glogarova at al. [69], it is shown how the properties of a liquid crystal cell can be modulated and stabilized using a ferroelectric material as an anchoring substrate. These results motivated us to consider that the EFM technique could be efficiently used to create surfaces with variable anchoring conditions on a micrometric scale. 

G. Joly, A. Anakkar, M. Ismaili, P. Cluzeau, N. Isaert, H.T. Nguyen, Chiral azobenzene liquid crystals under illumination Thickness influence and spontaneous polarisation variations. Ferroelectrics 277, 67-74 (2002)... 

In this book the authors present a complete and readily understood treatment of virtually all known phenomena occurring in liquid crystals under the influence of an electric field. In the first three chapters (Chapters 1-3) bulk and surface properties of liquid crystalline materials are discussed. The next two chapters (4, 5) are devoted to consideration of the electrooptical effects due to the formation of uniform and spatially modulated structures in nematics. In Chapters 6 and 7 the electrooptical properties of the cholesteric and smectic mesophases are presented, including a discussion of ferroelectric materials. Major emphasis is given to explaining the qualitative aspects of the phenomena and to portraying their physical basis. The prospects for the practical application of electrooptical effects are also discussed (Chapter 8). 

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. 

The helical smectic C state has the point symmetry (< 22), illustrated in Fig. 19, which does not permit a polar vector. It is therefore neither pyroelectric nor ferroelectric. Nor can it, of course, be piezoelectric, which is also easily realized after a glance at Fig. 14 if we apply a pressure or tension vertically, i.e. across the smectic layers (only in this direction can the liquid crystal sustain a strain), we may influence the pitch of the helix but no macroscopic po-... 

Boiko N, Zhu X, Vinokur R, Rebrov E, Muzafarov A, Shibaev V (2000) New carbosilane ferroelectric liquid crystalline dendrimers. Mol Cryst Liq Cryst 352 342—350 Botiz I, Stingelin N (2014) Influence of molecular conformations and microstructure rat the optoelectronic properties of conjugated polymers. Materials 7 2273-2300 Bumiing TJ, Natarajan LV, Tondiglia VP, Sutherland RL (2000) Holographic polymer dispersed liquid crystals (HPDLCs). Armu Rev Mater Sci 30 83-115 Busch K, John S (1999) Liquid-crystal photonic-band-gap materials the tunable electromagnetic vacuum. Phys Rev Lett 83 967-970... 

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