Smectic membranes thermotropic

Thermotropic smectic membranes are similar to the Newton black soap films in respecf to their structure, thickness, and because both are spanned on frames and can exchange molecules with the meniscus. However, the smectic membranes are more complex in the respect that the number N of monolayers is variable, whereas the Newton black films are usually bilayers. Smectic membranes are also similar to vesicles by means of their layered structures however, the vesicles are rather isolated unframed systems in the sense that the number of molecules is conserved, but the surface is free to evolve. ... 

We note that earlier research focused on the similarities of defect interaction and their motion in block copolymers and thermotropic nematics or smectics [181, 182], Thermotropic liquid crystals, however, are one-component homogeneous systems and are characterized by a non-conserved orientational order parameter. In contrast, in block copolymers the local concentration difference between two components is essentially conserved. In this respect, the microphase-separated structures in block copolymers are anticipated to have close similarities to lyotropic systems, which are composed of a polar medium (water) and a non-polar medium (surfactant structure). The phases of the lyotropic systems (such as lamella, cylinder, or micellar phases) are determined by the surfactant concentration. Similarly to lyotropic phases, the morphology in block copolymers is ascertained by the volume fraction of the components and their interaction. Therefore, in lyotropic systems and in block copolymers, the dynamics and annihilation of structural defects require a change in the local concentration difference between components as well as a change in the orientational order. Consequently, if single defect transformations could be monitored in real time and space, block copolymers could be considered as suitable model systems for studying transport mechanisms and phase transitions in 2D fluid materials such as membranes [183], lyotropic liquid crystals [184], and microemulsions [185],... 

The proper function of a membrane is intimately linked to the liquid-crystalline character of its lipid bilayer matrix. Among other factors, this depends crucially on the existence of sufficient water reservoirs on both sides of the bilayer membrane. (The lipid bilayer is a thermotropic and lyotropic smectic liquid-crystal.) While this is naturally given on the distal side of the tethered membrane architecture by the aqueous phase of the flow cell, the coupling of the membrane to the substrate on the proximal layer imposes serious restrictions on the amount and free accessibility, e.g., for ions of the aqueous phase between the bilayer and the solid substrate. In this context, the tethering system not only couples and thus stabilizes mechanically the whole architecture to the support foremost it has to decouple the lipid bilayer from the strong interactions of the headgroups with the polar support. This way ... 

Mesophases can be locked into a polymer network by making use of polymerizable LCs [59]. These molecules contain moieties such as acryloyl, diacety-lenic, and diene. Self-organization and in situ photopolymerization under UV irradiation will provide ordered nanostmctured polymers maintaining the stable LC order over a wide temperature range. A number of thermotropic liquid crystalline phases, including the nematic and smectic mesophases, have been successfully applied to synthesize polymer networks. Polymerization of reactive lyotropic liquid crystals also have been employed for preparation of nanoporous polymeric materials [58, 60]. For the constmction of nanoporous membranes, lyotropics hexagonal or columnar, lamellar or smectic, and bicontinuous cubic phases have been used, polymerized, and utilized demonstrated in a variety of applications (Fig. 2.11). 

In the classical view only membranes and their components seem tolerable, with their close bilayer similarities to thermotropic smectics and head/tail abstracted lyotropics [7a, 33p, q, 54-57]. While nucleic acids and proteins represent both structure and system individualities, membranes, as huge collectives of highly differentiated mem-... 

Lyotropic lamellar systems are very similar to thermotropic smectics, and their elastic free energy is identical to that of SmA given in Eq. (4.34). In lyotropic lamellar systems, the origin of the layer compression modulus B is the steric repulsive interaction energy. This can be visualized as illustrated in Figure 4.20. If a stack of membranes, formed, e.g., by lipid bilayers, is placed between two parallel walls, violent thermal out-of-plane fluctuations of the membranes exert a pressure p on the walls. 

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