Smectics orthogonal

FIG. 33 X-Ray Diffraction Patterns of Ammonium Dodecane 1-Sulfonate. 2-D (a) and 3-D plots (b) of oriented samples. Both pictures show the presence of a nonordered smectic phase, since the diffuse, weak, wide-angle diffraction indicates only an average distance between the molecules and the sharp, intense small angle reflections a very well defined layer distance. The reflections are perpendicular to each other, so the structure should correspond to an orthogonal smectic A type. The pictures were obtained using an x-1000 area detector from Siemens. 

In this section, we will present the crystal structures of chiral mesogenic compounds exhibiting ferroelectric liquid crystalline phases which are listed in Table 18 [152-166]. Moreover, four compounds of the list show antiferroelectric properties and two compounds form only orthogonal smectic phases. The general chemical structures of the investigated chiral compounds are shown in Fig. 27. 

The structure of the B6 phase is also illustrated in Figure 8.17. This achiral, orthogonal smectic phase is one of the class of intercalated smectics wherein the layer spacing is actually about half the molecular length. This phase, which has full translational symmetry within the layers, has the same symmetry (D2h), and the same basic structure as the all-anticlinic SmCA phase. Intercalated SmCA phases of this type were first described in pioneering work of Watanabe in main-chain polyesters.37... 

The electroclinic effect is an induced molecular tilt observed in the chiral orthogonal smectic phases, such as the smectic A phase, when an electric field is applied along the smectic layers [76]. The induced molecular tilt 0 is a linear function of the applied field E and gives rise to an induced polarization Pj... 

V. Novotna, M. Glogarova, M. Kaspar, V. Hamplova, E. Gorecka, D. Pociecha and M. Cepic, Reentrant orthogonal smectic-A phase below a tilted smectic-C phase in a chiral compound, Phys. Rev. E 83(2), 020701/1-4, (2011). doi 10.1103/PhysRevE.83.020701... 

Figure 11 The mosaic textures of smectic phases showing the side elevations of the domains (A) the orthogonal smectic phases and (B) the mosaic texture of a smectic phase where the long axes of the molecules are tilted with respect to the layer planes.

Panarin, Y. R Nagaraj, M. SreenUayam, S. Vij, J. K. Lehmann, A. Tschierske, C. Sequence of four orthogonal smectic phases in an achiral bent-core liquid crystal evidence for the SmAPoi phase. Phys. Rev. Lett. 2011,107, 247801. 

Introduction of chirality into the chemical structure of a liquid crystal molecule has no effect on the structure of orthogonal smectic phases (e.g., smectic A). Ne-... 

Due to special symmetry conditions, the presence of chiral molecules in tilted smectic phases leads to the appearance of a spontaneous electric polarization within each smectic layer [1], [2], Magnitude and direction of the polarization are coupled to the magnitude and direction of the molecular tilt giving rise to imique properties of tilted as well as orthogonal smectic phases of chiral molecules in external electric fields. In this chapter, the basic properties of smectic-C and smectic- l phases of chiral low-molecular weight molecules are summarized, mainly from the viewpoint of physics. 

Under the second column of Table 1.1, different orthogonal smectics are classified according to the structures within the layers. Smectic A has layers that can be considered as simple two-dimensional liquids. There is only short-range correlation between the molecular positions within the layers over a distance corresponding to a few molecules. In Fig. 1.5a, two of these short-range clusters of size are shown. These clusters possess a... 

SmA chiral orthogonal smectic A SmB / chiral orthogonal hexatic smectic SmBjfgx B phase (SmB preferred)... 

It will be seen that most nematics and orthogonal smectic and columnar phases are... 

Achiral calamitic orthogonal smectic or lamellar phases (SmA) D hXT(2) u(+)... 

Orientation of the transverse molecular dipole moments become biased along the y-axis (corresponding to above) when a tilt develops either induced by an electric field along the y-axis (orthogonal smectics) or... 

Hz. The high frequency polarization modes (<%s> pg) essentially the same as the dipole relaxation modes for x already discussed in the context of non-chiral phases, except they relate to a linear transverse dipolar contribution to the permittivity they are degenerate in orthogonal smectic phases, and have relaxation frequencies in the region of 500 MHz. The temperature dependence of these relaxation processes is illustrated schematically in Fig. 21. 

Transitions between Tilted and Orthogonal Smectic Phases... 

Electroclinic Effect Near the Smectic A—Smectic C Phase Transition. The electric field may induce a tilt of the director in the orthogonal smectic A phase near the smectic A-smectic C phase transition (electroclinic effect [189, 191]). The electroclinic effect may be understood within framework of the Landau phase transition theory [7]. If the dielectric anisotropy is negligible, the free energy density of the smectic A phase may be expanded over the field-induced tilt angle 6 ... 

This chapter is concerned with the application of both tilted and orthogonal smectic phases that do not contain a chiral center, within these constraints it is the smectic A phase (SmA) that is of most interest and has been most widely studied. 

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