Tilted molecules

This region has been divided into two subphases, L and S. The L phase differs from the L2 phase in the direction of tilt. Molecules tilt toward their nearest neighbors in L2 and toward next nearest neighbors in L (a smectic F phase). The S phase comprises the higher-ir and lower-T part of L2. This phase is characterized by smectic H or a tilted herringbone structure and there are two molecules (of different orientation) in the unit cell. Another phase having a different tilt direction, L, can appear between the L2 and L 2 phases. A new phase has been identified in the L 2 domain. It is probably a smectic L structure of different azimuthal tilt than L2 [185]. 

Chiral molecules which form smectic liquid crystals are often capable of forming structures in which the electric dipoles associated with the molecules all point approximately in the same direction in a particular region but in which this direction rotates as one moves in a direction normal to the smectic planes. Such materials are rather misleadingly referred to as ferroelectric liquid crystals. The mechanism responsible for this effect is illustrated in Figure 7.3. The molecules tilt into a smectic-C phase due to their structure as illustrated. Dipoles associated with the molecules are supposed to point in a direction normal to the page. Thus, if the molecules all have the same handedness the dipoles all point in he same direction. This description is an oversimplification as the molecules rotate about their long axes but point preferentially in the manner indicated. This phenomenon has been successfully applied to... 

Dividing (2) by F, it is clear that the area would tend to 85 sq. A. at high surface pressures, if the physical conditions of this part of the curve were maintained (this is not actually the case, as the molecules tilt, and occupy much less space in gaseous films at high compressions). The value of the first constant on the right of (2) is an indication of the area of the molecules lying flat, but it usually gives results which are rather too small. 

Molecules Tilted in Diffuse Layeis No Long Range PosMonai Order Long Range Hit Older... 

Figure 15. Schematic illustration of a chiral bilayer (A), with the molecules tilted with respect to the local layer normal. (The arrows indicate the direction of the molecular tilt, projected into the layer plane.) The favored twist between the chiral molecules leads the whole membrane to curve into (B), a wound ribbon, then fuse into (C), a cylindrical tube. The observed CD spectra come from the chiral molecular packing common to all three figures, not from the micrometer-scale helical structure in (B) and (C). Reproduced from ref. 171 (Schnur et al.. Science 1994,264,945) with permission of the American Association for the Advancement of Science.

Molecules Tilted In Diffuse Layers No Long Range Positional Order Long Range Tilt Order... 

It is well accepted that innate and adaptive immune mechanisms modnlate atherosclerosis [1,2] and immune responses to OSEs, such as OxPLs, play a central role in the development of atherosclerosis. [3] Following lipid accnmnlation in the vessel wall, atherosclerosis develops when the net balance between snbsets of immune cells and their products, such as proinflammatory and anti-inflammatory subsets of macrophages, B-1 cells and B-2 cells and their respective IgM and IgG antibodies, T effector cells and Tregs and co-stimulatory and co-inhibitory molecules tilts toward a pro-inflammatory phenotype [4]. 

Assuming the head-to-tail symmetry of a bent-shape molecule, the highest symmetry of a uniaxial non-tilted smectic A layer is Dooh- Then, according to molecular packing presented in Fig. 13.29a, the highest symmetry of the biaxial polar layer is 2, there is a rotation axis C2 parallel to x, and two symmetry planes xz and xy. The layer polarization is possible along the C2 axis. Had the layer consisted of the rod-like molecules tilted within the xz plane the symmetry would be C2h as in SmC. However, when the bent-core molecules are tilted in the y-direction (forward... 

The simplest phase corresponds to a compact triangular packing (still called hexagonal) of isotropic columns (see Fig. 9.3). The equivalent phases in smectic C liquid crystals are such that molecules are tilted relative to columns. A priori molecules may tilt towards the nearest or second nearest neighbour columns, or in any other direction. These three possibilities correspond to three distinct phases. Columns may also deform themselves into ellipses without molecules tilting relative to the columnar axis this is yet another phase. Columnar symmetry may also occur with local smectic order and an example is shown in Fig. 9.19 for long thin molecules with polar heads. All these phases have common elastic, hydrodynamic and topological properties. 

SAMs on metal oxide surfaces, a model assuming a uniform, dense packing of molecules tilted by an angle of 30° to the surface normal was used (Figure 9). 

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