Structures lamellae

A comparison of the calculated relative peak heights using the very simplified electron density profiles of Figs. 23b and 23d with the SAXS pattern of the sample, Fig. 24, unequivocally indicates the presence of the non-centrosysmmetric lamellae structure depicted in Fig. 23a. In agreement with SCMF calculations [90], the centrosymmetric two-way arrangement (Fig. 23c) of A-B-C-A-C-B pattern was not observed. 

The BET surface area of the catalysts is summarised in Table 3. The enhancement could be explained in case of MO-s with the reconstruction of the lamella structure. The reason of enhancement in the presence of 212 is still not known. All the other cases significant decrease can be observed. The surface area of metallic part of the used RNi-s shows increase from A to C, with the increasing temperature of the catalyst production, indicating growing Ni distribution. 

With the long alkyl chain substitutions on the A-heterocyclic carbenes, lamella-structured silver(i) carbene complexes 27a and 27b (Figure 14) were isolated.74 It is interesting to note that the synthetic procedures for the two complexes are the same except for the use of different solvents of crystallization. The dinuclear 27a was obtained from recrystallization in dichloromethane- -hexane while the tetranuclear 27b was obtained from acetone. The structure of 27a could be interpreted as the dimeric form of [Ag(carbene)Br] bridged by intermolecular Ag-Br interactions. The Ag-G bond has a distance of 2.094(5) A. The tetranuclear 27b, on the other hand, could be regarded as two monocationic bis(carbene)silver(i) bridged by an [Ag2Br4]2 anion, with the presence of short Ag(cationic)-Ag(anionic) contact (3.0038(18) A) and comparable Ag-G bond distances (2.0945(5), 2.138(13) A). A related... 

X-ray diffraction from cast films provide useful information of bilayer structure. Periodic peaks in small and middle-angle diffraction from cast films on glass plates are attributed to the reflections from (h, 0,0) planes of the multiple lamella structure. The spacing of higher order reflections (h > 1) satisfies with numerical relation of 1 / h of the long period calculated from the first order reflection =1), which is equivalent to the bilayer thickness. Every cast film measured in this experiment showed more than 6 reflection peaks. 

Wide-angle X-ray scattering data of these films is not consistent with the phase segregation of the core and complex units, although a lamellae structure is observed... 

Okano et al. [78-80] found that HEMA-STY triblock copolymer formed a typical domain structure when it was cast into a film. The domain structure changed with the HEMA mole fraction, and the lamella structured surface (mole fraction of HEMA 0.61 lamella width 30-50 nm) exhibited the best blood-compatibility. 

In mean field theory, two parameters control the phase behavior of diblock copolymers the volume fraction of the A block /A, and the combined interaction parameter xTak- V. where Xab is the Flory-Huggins parameter that quantifies the interaction between the A and B monomers and N is the polymerization index [30], The block copolymer composition determines the microphase morphology to a great extent. For example, comparable volume fractions of block copolymer components result in lamella structure. Increasing the degree of compositional asymmetry leads to the gyroid, cylindrical, and finally, spherical phases [31]. 

Both theoretical [186, 190-192] and experimental [63,123,124, 128, 193] studies have demonstrated that interaction of the middle B block with a substrate plays a decisive role in the lamella structure orientation and order in thin films. 

Xiao et ah, 2007). The results indicate that the regular parallel lamella structure (the concentric cylinder barrel structure) appears if d and L0 are compatible in both flat and curved confinements, while a vertical or distorted vertical lamellae structure (sector column structure) is observed otherwise. Upon increasing the curvature of the exterior surface K = 1 /ReXr the compatibility span of d and L0 becomes smaller consequently, the formation of the parallel lamella structure (or the concentric cylinder barrel structure) is more difficult. Our MC results in this work are shown in Figure 28 and more details can be referred to (Xiao et ah, 2007). 

Figure 21.8 Structural models for lamellar PEP-fr-PEO-b-PHMA block copolymer-aluminosilicate composite morphologies with a small PEP block. In the absence of the PEP block, the PEO (black) and PHMA (light grey) chains stretch into their respective domains while the aluminosilicate particles (white) partition into the hydrophilic PEO domain (a). Possible domain structures discussed in the text are illustrated as follows In the balls-in-lamellae structure the small PEP block (dark grey) forms round micellar domains (b). Dimple structure with PEP micelles at the PHMA/PEO-aluminosilicate interface (c). In the pillared-lamellae structure the PEP domains form pillars spanning across the PEO-aluminosilicate domain (d).37 (Reprinted with permission fiomG.E. S.Toombesetal., Chem. Mater. 2008,20,3278-3287. Copyright 2008 American Chemical Society.)...

Figure 21.12 Structural models for PEP-fr-PEO-fr-PHMA block copolymer-aluminosilicate lamellar morphologies with a small PEP block. Top (a) and side (b) views of the pillared-lamellae structure.37 (Reprinted with permission from G. E. S. Toombes et al., Chem. Mater. 2008, 20, 3278-3287. Copyright 2008 American Chemical Society.)...

Fig. 16 STM images (b 11.7x 11.7 nm2, c 11.5 x 11.5 nm2) and structure models (d,e) for the enantiomorphous lamella structures induced by adsorption of ISA (a) on hopg from a 1-heptanol solution [47]. For opposite enantiomers, opposite lamella tilt angles (0) are observed. The large lamella ALi is built up from pure ISA enantiomers, while the smaller AL2 lamella consists of coadsorbed achiral 1-heptanol molecules. The ISA chirality is transferred to the coadsorbed solvent molecules via opposite alignment angles (p (f,g). Reprinted with permission from Wiley...

There are relatively few direct transmission, electron microscopy (TEM) studies of domain structures in polyurethanes (3-7,13,14,15). No distinct micelle-lamellae platelets have been observed in the urethane systems thus studied. Instead, the domain structures which have been observed generally appear as isolated equiaxed grains 30-500 A in diameter (4,13,14,15). Randomly oriented fibrils with lateral dimensions of 300-600 A have been observed in a polyether/MDI/BDO system (3,6). It remains to be seen what relation the equiaxed grains (domains) and the fibrils observed by transmission electron microscopy have with the micelle-lamellae structures inferred from WAXS and SAXS (12,16). 

A constricted tube model is used to analyze viscous and capillary effects associated with foam flow in porous media. The foam moves through the pore structure as single layer, continuous bubble trains. Capillary resistance stems from the drainage and imbibition surfaces as well as the internal lamellae structure. 

In order to obtain an estimate of such effects, the pressure associated with the capillary resistance of the internal lamellae structure was calculated for different sets of bubbles, with different numbers and sizes. The specific pore geometry chosen was that shown in Figure 3. The pressure is the pressure in the front bubble and pressure Pn is that of the Nth bubble Pn - Po then gives the capillary resistance associated with the internal... 

The results for bubble trains with 100 bubbles (Figure 4(a)) show that the capillary contributions associated with the internal lamellae structure are significant and result in mobilization pressures (Pn) as high as 9 times the capillary pressure of the... 

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