Template leaching

Template leaching is another methodology applied for the production of membranes it can be applied to produce porous glass membranes [180], The method consists in the formation of a structure with the help of a homogeneous melt of a three-component system, for example, NazO—B203 — Si02 when 

FIGURE 3.18 SEM micrograph of a ceramic membrane prepared with a powder of particle size, dp = 500 pm, and treated at 800°C, During 2h. (bar = 1 pm). 

The Physical Chemistry of Materials Energy and Environmental Applications 

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Figure 3.6 Flow schematic of a melt extruder system used to make polypropylene membranes by template leaching [13]...

Symmetric membranes and asymmetric membranes are two basic types of membrane based on their structure. Symmetric membranes include non-porous (dense) symmetric membranes and porous symmetric membranes, while asymmetric membranes include integrally skinned asymmetric membranes, coated asymmetric membranes, and composite membranes. A number of different methods are used to prepare these membranes. The most important techniques are sintering, stretching, track-etching, template leaching, phase inversion, and coating (13,33). 

J. Sa-nguanruksa, R. Rujiravanit, P. Supaphol, and S. Tokura, Porous polyethylene membranes by template-leaching technique preparation and characterization. Polymer Testing 23, 91-99 (2004). 

Similarly not aU template molecules may be accessible within the polymer matrix, or will require very long extraction times leading to problems of template leaching especially when employing MIPs for trace analysis [35]. 

The effects of both template and amine ligands were examined for the reduction of acetophenone derivatives with the rhodium catalysts (Table 4). The reduction of propiophenone using P-8a, b was also examined to eliminate the possibility of the template leaching to distort the product analysis (entry 7). The enantioselectivity was the highest reported of the series, although the results were still unremarkable when compared to the homogeneous examples. 

The template leaching technique is suitable for preparing porous membranes from polymers, which do not dissolve in common organic solvents [9], or from glass, metal alloys, and ceramics [5]. 

There are important limitations to consider when using MIPs in sensing applications. These include their recognition properties in water, binding kinetics, and slow leaching of the template from the polymer matrix. 

Template Polymers. Template effects in chelating polymers constitute an interesting development in the field of metal containing polymers. The Template effects are interpreted by the fact that the small molecule is templating a pattern in the macromolecule which can be recognized by the same molecule in a subsequent process. The idea is to prepare a polymer from the metal-chelated monomer, to remove the metal ion, and then to measure the selectivity of the prepared polymer for the metal ion of the template [36]. Typical examples of template systems are 4-vinyl-4 -methylbipyridine (Neckers [36]) and 1-vinyl-imidazole (Tsuchida [37]). These are polymerized in presence of divinylbenzene [36] and appropriate metal salts (Co2+, Cu2+, Ni2+, Zn2+). The template metal ions are removed by acid leaching and the polymer subsequently used for metal ion absorption studies (Fig. 16). 

Early reports on electrospun scaffolds described poor cellular infiltration [175], Frequently, cells adhered at the surface and thus coated the nano- or submicrometer-scaled electrospun meshes due to the small pore size. In order to overcome this limitation, pore sizes were increased by combining ES with other methods. These approaches included the coating of microfibers with nanofibers [183], Other strategies combine ES with leaching [184, 185], freeze-drying [186], blowing agents [187], or ice templates [188],... 

Figure 5.17. Screen-shots from ADEPT. (a)A simple two-component library composed of an ami-nothiazole template and a series of piperidines specified with ADEPT. (b) Histograms of rotatable bonds and molecular weight for the enumerated virtual library, aiding the medicinal chemist in the design of the library. [Reproduced from A. R. Leach and M. M. Hann, Drug Discovery Today, 5, 326-336 (2000), with permission of Elsevier Science.]...

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