Crystallographical regularity

Intercalated composites in an intercalated composite the insertion of polymer into the clay structure occurs in a crystallographically regular fashion, regardless of the clay to polymer ratio. An intercalated nanocomposite is normally interlayered by only a few molecular layers of polymer and properties of the composite typically resemble those of ceramic materials. 

They retain the domain structure of filler and consist of ordered regions (crystallographically regular) formed by slightly exfoliated filler domains. 

In the first case polymer chains are inserted into layered structures such as clays, which occur in a crystallographically regular fashion, with a few nanometres repeat distance, irrespective of the ratio of polymer to layered structure. In the second case, flocculation of intercalated and stacked layers to some extent takes place due to the hydroxylated edge-to-edge interactions of the clay layers. Finally, separation of the individual layers in the polymer matrix occurs in the third type by average distances that depend only on the loading of layered material such as clay. In this new family of composite materials, high... 

Intercalated. Where the insertion of the polymeric chains into the layered silicate structure occurs in a crystallographically regular fashion and at a constant spacing of a few nanometers. 

Intercalated Nanocomposites Where insertion of polymer chains into the silicate stracture occurs in a crystallographically regular fashion, regardless of polymer to OMLS ratio, and a repeat distance of few nanometers. Intercalated morphologies are characterized by moderate intrusion of polymer strands into the gallery volume and the shape of the layered stack is preserved. 

The best fit of the Nielsen model (Equation 11.3) to the experimental data for O2 and water gave apparent particle aspect ratios of 46 and 130, respectively. Chang et al. suggest that the clay retains a crystallographic regular layer... 

One of the most striking results that has emerged from the high-resolution crystallographic studies of these icosahedral viruses is that their coat proteins have the same basic core structure, that of a jelly roll barrel, which was discussed in Chapter 5. This is true of plant, insect, and mammalian viruses. In the case of the picornaviruses, VPl, VP2, and VP3 all have the same jelly roll structure as the subunits of satellite tobacco necrosis virus, tomato bushy stunt virus, and the other T = 3 plant viruses. Not every spherical virus has subunit structures of the jelly roll type. As we will see, the subunits of the RNA bacteriophage, MS2, and those of alphavirus cores have quite different structures, although they do form regular icosahedral shells. 

Our laboratory has planned the theoretical approach to those systems and their technological applications from the point of view that as electrochemical systems they have to follow electrochemical theories, but as polymeric materials they have to respond to the models of polymer science. The solution has been to integrate electrochemistry and polymer science.178 This task required the inclusion of the electrode structure inside electrochemical models. Apparently the task would be easier if regular and crystallographic structures were involved, but most of the electrogenerated conducting polymers have an amorphous and cross-linked structure. 

The crystallographic structure of the D. vulgaris protein has been reported by Lindley and collaborators (132). The structure was solved to a resolution of 1.7 A. The major findings are consistent with most of the conclusions derived from the Mossbauer work done in the D. desulfuricans protein. The protein was found to contain two distinct clusters of the same nuclearity. Also, one cluster has a mixed N, O, S ligand environment, while the other has a regular iron-sulfur core... 

A regularly formed crystal of reasonable size (typically >500 pm in each dimension) is required for X-ray diffraction. Samples of pure protein are screened against a matrix of buffers, additives, or precipitants for conditions under which they form crystals. This can require many thousands of trials and has benefited from increased automation over the past five years. Most large crystallographic laboratories now have robotics systems, and the most sophisticated also automate the visualization of the crystallization experiments, to monitor the appearance of crystalline material. Such developments [e.g., Ref. 1] are adding computer visualization and pattern recognition to the informatics requirements. 

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