Encapsulation compounds

Increased sophistication in chemical synthesis has led to the development of a wide range of molecules which can wrap up or encapsulate metal ions (as well as, in some cases, even whole small molecules). A range of topologies (or three-dimensional shapes) has been devised for accommodation of either metal ions with different preferred coordination numbers or small molecules. The former usually involve covalent bonds, the latter weaker nonco-valent interactions (such as hydrogen bonds). Developing functionality for encapsulated 

Examples of three-, four-, five- and six-donor macrocycles. Metal ion selection and binding strength 

At a simple level, we can see this as four up , three up and one down , and two types of two up and two down other options (such as four down compared with four up ) are 

Possible dispositions of the secondary amine hydrogen atoms in a coordinated macrocyclic tetraamine. Each isomer, formed only on coordination, exhibits slightly different physical properties. 

A simple macrobicycle can be considered to arise by addition of another chain or strap of atoms to a macromonocycle, to provide three chains joined at two capping carbon atoms (top), effectively two fused macromonocycles. This example offers six donor groups to a metal ion, as exemplified with ball and stick and space-filling models the latter shows the small central cavity able to accommodate only a single cation. These readily form very stable octahedral complexes with a range of metal ions the best-known example has L = NH (called sarcophagine ). 

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Casting resin Thermoplastic elastomer Cast resin, flexible Mineral- and/or glass-filled Epoxy molding and encapsulating compound Polystyrene... 

Thermosetting-encapsulation compounds, based on epoxy resins (qv) or, in some niche appHcations, organosiHcon polymers, are widely used to encase electronic devices. Polyurethanes, polyimides, and polyesters are used to encase modules and hybrids intended for use under low temperature, low humidity conditions. Modified polyimides have the advantages of thermal and moisture stabiHty, low coefficients of thermal expansion, and high material purity. Thermoplastics are rarely used for PEMs, because they are low in purity, requHe unacceptably high temperature and pressure processing conditions. 

Efficiency of encapsulation amount of the encapsulated compound divided by the total amount added to the preparation. 

Thermoset polyurethanes, 25 460-461, 476 Thermosets, 10 456, 20 390 Thermoset sealants, 22 35 Thermosetting-encapsulation compounds, 17 839... 

Photons with detectable energy differences that are emitted by various radionuclides can be quantified simultaneously, but independently from each other. This allows the use of dual-labeling approaches (4). These experiments will reveal information regarding both the liposomal carrier—labeled with one radionuclide—and the encapsulated compound—labeled with a different radionuclide—after a single injection in the same animal. However,... 

One advantage of liposome is theirsingularability to take up material of all shapes and sizes regardles of their individual chemical peculiarities. The most relevant to this discussion is for lipid-soluble compounds, which are incorporated into the lipid bilayer of the liposome. Thus, the maximum amount taken up into liposomes is directly proportional to the quantity of membrane components, but is independent of the size of the liposomes used, except in a few cases where the structure o the encapsulated compound may restrict the Lnal size of the liposome. Theoretically, any type of liposome is suitable for the incorporation of lipid-soluble substances, but practical considerations make some choices more preferable over others. MLVs are the best choice for sustained release whereas SUVs are particularly suitable for rapid intermembrane transfer. 

The final types of materials that may cause you problems in extraction are membrane-bound or encapsulated compounds. In the past, these have been removed by adding detergent to break the membrane, pulling everything in to solution and then extracting out the compound of interest. It is difficult to get clean separations because of the soap emulsification that is created. The detergent often contaminates the subsequent chromatography. 

Labrousse, S., Roos, Y., and Karel, M. (1992). Collapse and crystallization in amorphous matrices with encapsulated compounds. Sci. Aliments 12, 757-769. 

Evolution of Epoxy Encapsulation Compounds for Integrated Circuits A User s Perspective... 

In previous publications, different probes and drugs have been encapsulated successfully in the pH-sensitive liposomes described in this chapter (3-9). The vesicles alone have been shown to be stable for prolonged periods of time (over months), when stored at 4°C. However, depending on the nature of the encapsulated compounds, content may degrade or leak upon storage, reducing the overall shelf-life of the formulation. 

Use Tire carcasses and linings, especially for tractors and other outsize vehicles electric wire insulation encapsulating compounds steam hose and other mechanical rubber goods pond and reservoir sealant. Latex is used for paper coating, textile and leather finishing, adhesive formulations, air bags, tire vulcanization, self-curing cements, pressure-sensitive adhesives, tire-cord dips, sealants. 

Monastrip [ICI], TM for a solvent stripper for uncured and cured epoxy, polyester, and silicone rubber casting and encapsulating compounds. 

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