Cooperative structure-directing

S.J. Weigel, S.C. Weston, A.K. Cheetham, and G.D. Stucky, Cooperative Structure Direction in the Synthesis of Microporous Materials Preparation and Crystal Structure of TREN-GaPO. Chem. Mater., 1997, 9, 1293-1295. 

We have developed an automated parallel synthesis methodology that permits the rapid and detailed Investigation of hydrothermal systems. The general procedure is as follows automatic dispensing of reagents into autoclave blocks followed by synthesis, product isolation and automated structure analysis with X-ray diffractometry. Here we describe the application of this technique to the exploration of the aluminophosphate synthesis field. The effects of template, template concentration, A1 sources as well as mixed template systems are investigated. Emphasis is put on the study of cooperative structure direction effects. 

Figure 3.4 Formation of mesoporous materials by structure-directing agents (a) true liquid-crystal template mechanism, (b) cooperative liquid-crystal template mechanism.

This kind of direct cooperation between organizations resembles a graphlike network cooperation structure in a peer-to-peer mode which is not supported in the former delegation-based concept of AHEAD Both subcontractors cannot cooperate with each other directly but only through their common contractor, the chemical company (shown in the left part of the Figure). In this way, only tree-like cooperation structures are possible. Although this delegation-based process decomposition approach is sufficient in many situations, often direct cooperation between all partners of a cooperative network of companies is needed as well. 

Four new informatics concepts were introduced in Sect. 1.1 and discussed in detail in Chap. 3 Direct process support based on developers experience, consistency control between different developers results based on underlying structures, direct communication between developers that is related to organized cooperation, and reactive management being able to cover the dynamic situations within design processes. These concepts are new and give valuable support within development processes, as to be seen from the demo description of Sect. 1.2. 

On the other hand, the soft template method involves cooperative assembly between the structure-directing agents (usually surfactants) and organic precursor species in solution. Therefore, the carbon structures obtained via soft templating are more flexible and their formation is dependent on temperature, type of solvent and ionic strength. However, there are currently only limited examples for the successful fabrication of porous carbon via the soft template method, which were reviewed recently by Wan et alP Soft template and hard template routes have been classified as endotemplate and exotemplate, respectively. 

Figure 20.3.5 Synthesis of the zeotypes SIZ-2 and A1PO-CJ2 using a ChCl/Urea DES. The structure directing agents have been omitted for clarity. [Adapted, by permission, from E. R. Cooper, C. D. Andrews, R S. Wheatley, P. B. Webb, P. Wormald and R. E. Morris, Nature, 430,1012 (2004).]...

It has been demonstrated that chemical structure directly affects cooperativity. " To simplify the research, one amorphous polymer with a high molecular weight was chosen. Polymethyl methacrylate (PMMA) was purchased from Aldrich in the powder form. Gel permeation chromatography showed a Mw of 101,300 g/mol with a polydispersity of 1.967. 

In ionothermal synthesis, the ionic liquid acts as the solvent, and in many cases also as a template provider playing a structure-directing role in the formation of zeolites and open-framework structures. The use of [EMim][Br] led to the formation of open-framework aluminophosphates SIZ-1, SIZ-3, SIZ-4, SIZ-5, and SlZ-6, (Cooper et al. 2004 Parnham et al. 2006) and the use of choline chloride/urea mixtures led to SlZ-2 and A1PO-CJ2 (Cooper et al. 2004). The ionic liquids acted as both solvent and template provider. 

Applications of structured packing into ethylene plant s various column systems [119] have been successfully achieved, but the individual manufacturers must be consulted to use their most directly applicable pilot and commercial data, which are generally not published. The use of published general correlations should only be used for a first or approximation design, while the delicate or important final design must be performed in cooperation with the manufacturer. 

Point defects in solids make it possible for ions to move through the structure. Ionic conductivity represents ion transport under the influence of an external electric field. The movement of ions through a lattice can be explained by two possible mechanisms. Figure 25.3 shows their schematic representation. The first, called the vacancy mechanism, represents an ion that hops or jumps from its normal position on the lattice to a neighboring equivalent but vacant site or the movement of a vacancy in the opposite direction. The second one is an interstitial mechanism where an interstitial ion jumps or hops to an adjacent equivalent site. These simple pictures of movement in an ionic lattice, known as the hopping model, ignore more complicated cooperative motions. 

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