Lamellar organization, effect

Fig. 7. Schematic diagram showing the effect of cooling rate on the lamellar organization of TAG and the t,. T is the initial temperature and is the isothermal crystallization temperature.

The dimeric A(LS)2 structure was found remarkably effective even in the case where the unit A is a ionic moiety, such as viologen in 54 [78], or a strongly self-associating group, such as the NAf -disubstituted 3,4,9,10-perylenetetracarboxylic diimide core in 55 [79]. It was foimd that 54 forms a stable gel only in 1-butanol at low concentration (below 1 wt/vol %) of which the CD spectnun displayed the features typical of a chiral, clockwise aggregation of the gelator molecules. X-ray diffraction patterns of the xero-gel of 54 were similar to those of the neat crystal obtained from ethanol. They indicated the formation of a lamellar organization with an interlayer distance of 4.96 nm. The molecules 54 were proposed to exist in an extended conformation in the gel state and to be tilted relative to the normal of the... 

Orientation affeets the permeability of polyethylene by changing its degree of crystallinity, lamellar organization, and molecular constraints. Strain-induced crystallization may increase the degree of crystallinity, while noncrystalline regions become better paeked as a function of orientation [47,48], both of which reduce the free volume of the system and hence reduce its permeability. Not withstanding, the effects of orientation are complex, and contradictory results have been reported [49]. 

These coatings are also employed as soHd lubricants in engine components. Refractory materials such as M0S2 and WSe2 are lamellar compounds and provide very effective soHd-state lubrication in spacecraft bearings and components used in radiation environments where conventional organic Hquid lubricants are not stable (see Lubrication and lubricants). 

An additional route consists of using the reconstruction ability of some LDH materials after a moderate thermal treatment. This is a pecuharity of LDH systems called the memory effect the LDH lamellar framework is reconstructed in the presence of the polymer with concomitant intercalation. Finally, a post-synthesis hydrothermal treatment can be applied in all cases, which may improve the inter- and intralamellar organization of the LDH/polymer nanocomposites. 

Figure 7 The possible mechanisms involved in the effect of penetration enhancers on the lipid organization of the intercellular domains in the stratum corneum. (A) Intercalation of the enhancer in the lipid lamellae. (B) Phase separation between enhancer and skin lipids in the lamellae. (C) Phase separation between lipid lamellae and an enhancer-rich phase. (D) Intercalation of the enhancer in the lipid lamellae and simultaneous phase separation between lipid lamellae and enhancer. (E) Phase separation within the lamellae and separation between an enahncer-rich phase and the lamellar phase. (F) Disappearance of the lamellar phases.

Fig. 2.4. The often dramatic effects bottom contacts can have on molecular ordering in organic semiconductors like pentacene. A. Schematic diagram of the type of disorder introduced in pentacene s lamellar structure as thin-film growth encounters a step, for example...

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