Microdomains crystallization

Figure 2.26 Model of packing of chains in form III of iP4MP according to space group /4x, 33. tS3 jwo eqUivaient unit cells characterized by chains having opposite azimuthal orientations indicating possible packing in different microdomains of crystal are shown.

Fig. 4 Schematic representation of control over block copolymer thin film orientation by directional eutectic solidification. The scheme shows control of polystyrene-b-polyethylene (PS-b-PE) block copolymer microdomain orientation through directional crystallization of benzoic acid (BA), (taken from [95])...

Cohen et al. (1990) studied a poly(styrene)-poly(ethylene) (PS-PE) diblock that was solvent cast from toluene. Crystallization within microphase-separated PE spheres occurred when solvent-casting was done above the PE block melting temperature, Tm (see Fig. 5.2). When solvent was removed below Tm crystallization did not occur within spherical microdomains, instead TEM and SANS experiments suggested an irregular structure. Nojima et al. (1994) suggest that crystallization from the melt in this sample occurred within the microphase-separated block in the former case due to the high molecular weight of the... 

The junction zones of CAQ organogel networks are lyotropic microdomains that vary from hexagonal in decane to more compact, lamellar-like ordering in 1-octanol 94. Schlieren optical textures confirm the inhomogeneity of the orientation of the threadlike structures (Fig. 16), and CD spectra resemble those of neat CAQ solid, cooled from its mesophase. However, the solid morph obtained from solvent crystallization is packed differently from the gel strands 114. ... 

Statistical thermodynamic treatments of defect populations have lead to an explanation of existence of grossly nonstoichio-metric crystals in terms of microdomains of ordered structure. The model considers that the nonstoichiometric matrix is made up of a mosaic of small regions of ordered defect-free structures, the microdomains. To account for stoichiometric variation, one can postulate that at least two microdomains with different compositions occur. However, compositional change might simply arise at the surface of the domain. For example, if there are compositionally identical microdomains, one of which is bounded by an anion surface and one by a cation surface, variation in the two populations can give rise to compositional variation. In a strict sense, as each microdomain is ordered, the concept of a defect is redundant, except for... 

Even though some plasma membranes, such as nerve myelin membranes, contain a high concentration of lipids that form gel phase bilayers, the presence of cholesterol keeps these membranes in a fluid phase. However, interaction with the rigid cholesterol ring affects hydrocarbon chains of lipids in the liquid crystal phase (L ) and leads to formation of a new phase, the liquid ordered (Lq) phase (27). The phase is well characterized by a variety of physical methods and does not exist in pure lipids or their mixtures. In the liquid ordered phase, the long axis rotation and lateral diffusion rates are similar to the La phase, but the acyl chains are predominantly in an all-trans conformation and, hence, the order parameters are similar to the Lp phase (see Table 1). Recently, the cholesterol-rich Lq phase has been strongly associated with microdomains in live cells—the so-called lipid rafts. ... 

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