Liquid analogous state

In contrast to the topochemically polymerizable diacetylenes, methacryloylic and butadienic lipids are also polymerizable in the liquid like phase. Figure 11 shows the contraction behavior of butadiene lecithin (19) during irradiation in the liquid analogous state 22). The final polymer has a 1,4-trans structure22). 

Fig. 5.20. Surface pressure (7r)/area (A) isotherm of a monolayer at the air-water interface a, gas analogous state 6, liquid analogous state c, condensed or solid...

Attaching non amphiphilic or amphiphilic liquid crystalline molecules as side chains to linear, branched or crosslinkedpolymers yields liquid crystal (l.c.) side chain polymers, which can exhibit the liquid crystalline state analogously to the conventional low molar mass liquid crystals. The l.c.-side chain polymers combine the specific, anisotropic properties of the liquid crystalline state with the specific properties of polymers. 

To function properly, cell membranes must exist primarily in the liquid-crystalline state. Model studies using synthetic lipids have demonstrated that the presence of a (9Z)-olefinic fatty acyl side chain in a diacylphospholipid lowers its gel-liquid phase temperature (T ) by some 50° C relative to its fully saturated analog (4). The presence of the A fatty acyl side chain lowers the T even more and constitutes an important adaptation to chilling for plants. The regulation of the response to chilling temperatures has been studied in some detail in various organisms (4). 

If the concentration of surfactant becomes high enough, surfactant structures often develop long-range order, and hence they become liquid crystalline. They are lyotropic liquid crystals, because the transition to the liquid-crystalline state is induced by concentration changes. Surfactant solutions can form nematic and smectic-A liquid-crystalline phases analogous to those discussed in Chapter 10. In addition, hexagonal and cubic phases are common in surfactant solutions. 

A polaron is an electron attached to, and moving with, the polarization induced by it in a polar environment. This concept is used mostly in solid state physics the liquid analog is the solvated electron. 

Another state of an excess electron is the delocalized which is sometimes called dry electron. The electron in this state is not localized in a definite microscopic region, but freely travels inside the liquid. This state is analogous to that of an electron in a conduction band. As the electron is not localized for a sufficiently long time, there is no possibility of the appearance of a corresponding polarization of a nuclear subsystem, in particular of orientation of dipoles. A delocalized electron interacts... 

These results were confirmed by Thompson et al., who investigated the thermal and mesomorphic behavior of Fc materials and those of analogous compounds in which Fc was replaced by a benzene or a cyclohexane ring (see, for example, 51-53).They observed that Fc destabilizes the liquid-crystalline state. Indeed, whereas 51 and 52 show enantiotropic SmC and SmA or SmC and N phases, respectively, 53 displays only a monotropic N phase. This behavior indicates that Fc plays the role of a bulky unit, again as a consequence of its three-dimensional structure. 

Analogous to three-dimensional bulk materials, monolayer films exhibit characteristics that can be almost equated to the solid, liquid, and gaseous states of matter. As the monolayer is compressed on the water surface, phase transitions between these analogous states should occur and the changes could be detected by the measurement of the n — A isotherms. Figure 7 shows an example of the n — A isotherm. It shows the following phases ... 

Many anion-driven supramolecular gels have been fabricated based on ion pairing or the analog state such as a mixture of acids and bases [8d]. There are a few examples of gelator molecules that are electronically neutral anion-responsive molecules, whose anion complexes also behave as gelators. This section mainly introduces several examples of anion-driven supramolecular gel systems as ion pairs, including ionic liquids and related materials, and cationic metal complexes accompanied by counteranions. 

Fig. 7. A texture of a main-chain liquid crystal polymer, X, as seen in transmitted light between crossed polars. By analogy with small molecule liquid crystal parlance, it is known as a Schlieren texture. The fine granular nature of the background is caused by crystallization on cooling otherwise the microstructure is unchanged from that in the liquid crystal state. (Photograph courtesy of T. J. Lemmon, Department of Materials Science and Metallurgy, University of Cambridge.)...

Conventional principles and methods concern the synthetic routes for macromo-lecular networks and the realization of the liquid crystalline state by mesogenic monomer tmits. Network chemistry has to consider the reactivity and functionality of the monomer tuiits. In most cases, this excludes ionic polymerization techniques and reduces utihzable methods to radical polymerization and polymer analog reactions for side chain networks, and to polycondensation or polyadditirai reactions for main chain elastomers. The chemistry of the crosslinking process and the chemical constitution of the crosslinker have to be adapted to the polymerization process. Applying photo-chemistry of suitable functional mmiomer units opens an additional, versatile pathway to build up the network structure. 

A vapor is in equilibrium with its liquid when the rate of condensation is equal to the rate of evaporation. An analogous state of equilibrium exists in a chemical system when the rate at which the reactants combine to form products is equal to the rate at which the products decompose to form the reactants. For example, in the stratosphere and mesosphere, ozone (O3) is formed by the reaction... 

Maier and Saupe [13] developed a statistical theory to describe the liquid crystalline state and the molecular ordering for the nematic phase. In analogy to the treatment of ordering phenomena in ferromagnetics or ferroelectrics, this theory describes the intermolecular orientational forces by a mean field method. Each individual molecule feels a nematic potential D = f (0, S, V) which depends on the momentaneous angle 6 between its long axis and the optic axis, the order parameter S and the molar volume V. S is then given by... 

K diverges in the vicinity of the N-SmA-SmC point where Cx vanishes. The type II condition is thus expected to be fulfilled close to the N-SmA-SmC point. In presence of chirality, this is precisely the place where a liquid crystal analog of the Abrikosov flux phase should show up. The structure of this new liquid crystalline state will be described in subsequent section. 

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