Chemistry of Synthesis

Pioneering workers in the field of polymer chemistry soon observed that they could produce polymers by two familiar types of organic reactions condensation and addition. As monomers react, new structures are created during the polymerization  

Polymers formed from a typical organic condensation reaction, in which a small molecule (most often water) is split out, are known, logically enough, as condensation polymers. The common esterification reaction of an organic acid and an organic base (an alcohol in this case) illustrates the simple lasso chemistry involved  

The —OH group on the alcohol and the on the acid are known as functional groups, 

In the above example, the reactants are monofimctional (there is one alcohol group on one reactant and one carboxylic acid group on the other) thus, if there are no other functional groups present in the rest of the molecule (the R group), the reaction will form only one new bond (an ester). Consider, though, what happens if both reactants are difunctional and the reaction progresses at each end. 

the resulting product molecule is still difunctional (an alcohol on the left end and 

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Polyimides (PI) were among the eadiest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, stmcture variations, and ultimately products and appHcations. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as stmctural composites, eg, over a ton of polyimide film is presently used on the NASA shuttle orbiter. Work continues on these materials, including the more recent electronic apphcations. 

The classical approach to the synthesis of nanostructured catalysts and materials of different morphologies and grain sizes has been one that heavily relies on detailed experimentation, altering the chemistry of synthesis to achieve the desired material. Our view has been that this approach, although successful for the synthesis of a wide range of nanostructured materials, requires too many experiments and is generally not a priori predictable. As a consequence, the direction of nanostructured materials synthesis in our laboratories has been to examine the application of various mechanical techniques that have sufficient process-parameter variability to afford... 

An alternative to this physical method of preparing structurally uniform metal clusters on supports involves chemistry by which molecular metal carbonyl clusters (e.g., [Rh6(CO)i6]) serve as precursors on the support. These precursors are decarbonylated with maintenance of the metal frame to give supported nanoclusters (e.g., Rh6). Advantages of this chemical preparation method are its applicability to many porous supports, such as zeolites (and not just planar surfaces) and the opportunities to use spectroscopic methods to follow the chemistry of synthesis of the precursor on the support and its subsequent decarbonylation. Zeolites, because their molecular-scale cages are part of a regular (crystalline) structure, offer the prospect of regular three-dimensional arrays of nanoclusters. 

Mochida I, Korai Y, Ku CH, Watanabe F, Sakai Y. Chemistry of synthesis, struetere, preparation and application of aromatic-derived mesophase pitch. Carbon 2000 38(2) 305-328. 

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