Ferroelectricity SmC* phase

Fig. 30 Selected examples of chiral rod-like mesogens with one fluorinated chain (77° C) one enantiomer is shown as example (SmCA = antiferroelectric SmC phase SmC = ferroelectric SmC phase SmCpi = ferrielectric SmC phase SmCa = helical SmC phase SmI = chiral tilted low temperature phase) [197-199]...

Earlier work on nanoparticle-doped chiral smectic-A (SmA ) and chiral smec-tic-C (SmC ) phases including some intriguing electro-optic effects in ferroelectric SmC phases were summarized in two earlier reviews [1, 2],... 

Measurements were performed on a SCE9 liquid crystal, which contains the ferroelectric SmC phase. The pure bulk SCE9 phase sequences with decreasing temperature from the isotropic (I) phase are as follows the I-N, N-SmA, and SmA-SmC phase transitions take place at 7) 392K,Tp 360K, and... 

The most studied chiral smectic phase is ferroelectric SmC phase [18], which is derived from Smectic C (SmC) phase. As shown in Fig. 5.2, the helical twist in SmC results from chiral organization of smectic layers as similar to the formation of N from nematic layers mentioned above. The molecules in each smectic layer... 

The flexoelectric effect is a phenomenon where a space variation of the order parameter induces polarization. Chiral polar smectics are liquid crystals formed of chiral molecules and organized in layers. All phases in tilted chiral polar smectic liquid crystals have modulated structures and they are therefore good candidates for exhibiting the flexoelectric effect. The flexoelectric effect is less pronounced in the ferroelectric SmC phase and in the antiferroelectric SmC. The flexoelectric effect is more pronounced in more complex phases the three-layer SmCpu phase, the four-layer SmCFi2 phase and the six-layer SmCe a phase. 

The structure of the ferroelectric SmC phase was described in detail in the previous section. We will repeat only the essentials. Molecules are tilted away from the layer normal, the tilt precesses around the cone from layer to layer but the direction differs between two layers only slightly. The tilts are almost synclinic. If the helicoidal modulation is neglected, we can say that... 

Then, for paraelectric SmA phase both = 0 and = 0, for ferroelectric SmC phase 0 but = 0 as discussed in Section 13.1, for antiferroelectric SmC A phase = 0 but f 0, and for ferrielectric phases SmC F/ both 0 and AP 7 0. Now the Landau expansion of the free energy in the vicinity of transitions between the paraelectric, ferroelectric and antiferroelectric phases will operate with two order parameters and both coefficients at the terms in the free energy are considered to be dependent on temperatiue ... 

Thennotropic and lyotropic liquid crystals share a common state of matter with many analogies in their structural and physical properties. However, these two fields of liquid crystal research are usually treated completely separately. This is partially due to historical reasons, but also to striking differences in some aspects of these two classes of liquid crystals. One of these differences is the occurrence of thermotropic phases which do not have a lyotropic counterpart A compelling example of this is the thermotropic ferroelectric SmC phase. Due to its unique chirality effects, i.e. ferroelectricity and a helical configuration of the tilt-direction, this phase attracted considerable scientific interest over the last decades. However, there are no reports found in literature about a SmC analog phase in lyotropic liquid crystals. 

In conclusion, this work shows that a lamellar, lilted, fluid phase exists in lyotropic liquid crystals and that it exhibits characteristic chirality effects, namely helicity and spontaneous electrical polarization, known Irom the thermotropic ferroelectric SmC phase. These results contribute significantly to a better understanding of lyotropic liquid crystals and bridge a substantial gap between the two fields of liquid crystal research. In accordance with the established nomenclature of lyotropic and thermotropic liquid crystals, the novel phase is suggested to be denoted as the lamellar L, phase, where the index a denotes a tilted fluid phase and the superscript indicates that molecules are chiral. 

The main non-display applications of liquid crystals can be subdivided into two classes. The first exploits their anisotropic optical properties in spatial light modulators or their nonlinear optical properties in optical wave mixing etc. Spatial light modulators are usually based on the ferroelectric SmC phase aligned in a thin film. Liquid crystal spatial light modulators may soon find advanced applications such as the storage of... 

Figure 9. Measured optical path difference for three and four layer smectic structures of antiferroelectric, ferrielectric and ferroelectric SmC phases [37]. Bottom figure indicates angle of incidence for A+ and A measurements.

In the ferroelectric SmC phase the tilt direction precesses in a helical path from layer to layer, whereas in the antiferroelectric... 

In smectic C materials, the relative twist of the planes is uncoupled to the layer thickness, giving rise to strong, nematic-like scattering [106]. There are relatively few light scattering studies of either achiral or chiral SmC phases, despite the technological importance of the ferroelectric SmC phase. This is in part due to the few discussions of the elastic theories of these phases, and in particular descriptions that include dynamic behaviour. Indeed it is only relatively recently that Leslie et al. [107] de-... 

Some of these materials display the potentially chiral ferroelectric SmC phase in addition to a SmA or cholesteric mesophase. Pyzuk [108] found for copper and nickel complexes some blue phase or novel type of amorphous phase between a tightly twisted chiral nematic phase and the isotropic liquid. These ferroelectric metallomesogens are interesting as they can be aligned par-... 

Busson P, Ihre H, Hult A (1998) Synthesis of a novel dendritic liquid crystalline polymer showing a ferroelectric SmC phase. J Am Chem Soc 120 9070-9071 Calundarm GW (1980) Melt processable thermotropic wholly aromatic polyester. US Patents 4184996... 

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