Nanostructure, lamellar

Scanning electron microscopy (SEM) is one of the very useful microscopic methods for the morphological and structural analysis of materials. Larena et al. classified nanopolymers into three groups (1) self-assembled nanostructures (lamellar, lamellar-within-spherical, lamellar-within-cylinder, lamellar-within-lamellar, cylinder within-lamellar, spherical-within-lamellar, and colloidal particles with block copolymers), (2) non-self-assembled nanostructures (dendrimers, hyperbranched polymers, polymer brushes, nanofibers, nanotubes, nanoparticles, nanospheres, nanocapsules, porous materials, and nano-objects), and (3) number of nanoscale dimensions [uD 1 nD (thin films), 2 nD (nanofibers, nanotubes, nanostructures on polymeric surfaces), and 3 nD (nanospheres, nanocapsules, dendrimers, hyperbranched polymers, self-assembled structures, porous materials, nano-objects)] [153]. Most of the polymer blends are immiscible, thermodynamically incompatible, and exhibit multiphase structures depending on the composition and viscosity ratio. They have two types of phase morphology sea-island structure (one phase are dispersed in the matrix in the form of isolated droplets, rods, or platelets) and co-continuous structure (usually formed in dual blends). 

Let us consider a nanostructured thin film built from lamellar particles [84], If the principal axis of layer stacks is oriented normal to the film surface, the scattered intensity measured in symmetrical-reflection geometry (SRSAXS) is... 

Ruland and Smarsly [84] study silica/organic nanocomposite films and elucidate their lamellar nanostructure. Figure 8.47 demonstrates the model fit and the components of the model. The parameters hi and az (inside H ) account for deviations from the ideal two-phase system. Asr is the absorption factor for the experiment carried out in SRSAXS geometry. In the raw data an upturn at. s o is clearly visible. This is no structural feature. Instead, the absorption factor is changing from full to partial illumination of the sample. For materials with much stronger lattice distortions one would mainly observe the Porod law, instead - and observe a sharp bend - which are no structural feature, either. 

Stribeck N (1980) Computation of the Lamellar Nanostructure of Polymers by Computation and Analysis of the Interface Distribution Function from the Small-Angle X-ray Scattering. Ph.D. thesis, Phys. Chem. Dept., University of Marburg, Germany... 

The morphology of spin-cast film, thickness of 180 nm, from polycaprolactone shows many spherulitic structures with fibrillar nanostructures formed of lamellae lying edge on (about 10 nm thick) and areas with lamellar sheets lying flat on. Different crystalline structures are found when the sample is melted and crystallized as a function of temperature. These two studies reinforce the complex inner relationship between physical treatment and nanostructure. 

Mesostructured aluminophosphate / surfactant composite materials were prepared from aqueous and alcoholic systems. Syntheses in ethanol or methanol, respectively, lead to mixtures of two nanostructured phases. One of these consists of hexagonally arranged rod-like assemblies of the surfactant molecules with the head groups located in the centres, encapsulating the inorganic aluminophosphate the other is lamellar. The syntheses were monitored by in-situ temperature- and time-resolved small angle X-ray scattering (SAXS). 

Fig. 25. The development of lamellar molecular crystals using polypeptides with a repeating sequence. The correct folding of these macromolecules produced by molecular biology gives peptide nanostructures, bearing specific functional groups in a well-defined spatial relationship. (Reproduced with the permission of Ref. 63)...

Figure 21.2 Assembly of mesosfructured hybrids, (a) Nanoparticles smaller than the darker gray block s R0 are miscible and assemble into a lamellar structure, (b) Nanoparticles larger than the darker gray block s R0 segregate, forming a nanoparticle-rich core around which lamellae assemble into an onion-type structure, (c) This can be used to generate compositionally heterogeneous nanostructures from tailored nanoparticle size distributions.10 (Reprinted with permission from S. C. Warren et al., Nature Mater. 2007, 6, 156-161. Copyright 2007 Macmillan Publishers Ltd.)...

Figure 16.15 Excitation of SPGCE on periodically modulated lamellar grating nanostructure with SPPs propagation, (a) The SEM images of Au (40 nm), Alq3 (80 nm) and photoresist, PR, (100 nm) fabricated on silicon substrate, (b) The 3-D AFM images of PR-grating profiles with 500 nm pitch size.

Recent studies by Lin and co-workers [63] have shown that not only the fatty acid composition influences the kind and ratio of carbonyls formed during heating of lipids, but also the structure of the reaction medium. The type of self-assembly stmcture had a significant influence on reaction yields. Egg phosphatidylcholin, which forms a lamellar phase together with water, generated significantly more 41 than phosphatidylethanolamine which adopts a different nanostructure, namely a reversed hexagonal structure. 

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