Polyhedral functionalized

The discovery of polyhedral boranes and polyhedral heteroboranes, which contain at least one atom other than in the cage, initiated a new era in boron chemistry.1-4 Most commonly, of the three commercially available isomeric dicarba-closo-dodecaborane carboranes(l,2-, 1,7-, and 1,12-), the 1,2-isomer 1 has been used for functionalization and connection to organic molecules. The highly delocalized three-dimensional cage bonding that characterizes these carboranes provides extensive thermal and kinetic stabilization as well as photochemical stability in the ultraviolet and visible regions. The unusual icosahedral geometry of these species provides precise directional control of all exopolyhedral bonds. 

Cole-Hamilton el al. reported one of the first dendritic effects. Dendrimers based on polyhedral oligomeric silsequioxane (POSS) cores were synthesized (Figure 4.26) the dendrons of this dendrimer were functionalized on the periphery with 8, 24 and 72 PR2 arms respectively (R = Me, Et, hexyl, Cy, or Ph).[36]... 

Polyhedral oligosilsesquioxanes and their homo derivatives have been prepared from monomers XSiYj with Y = OH, Cl, OR. The monomers with X = Br, I, OCOR, OM (M = Na, K), NRj, etc. may also be used. The reactivity of the functional groups decreases in the following order ... 

Several chemical synthesis routes to black glass precursors have also been developed, as will be discussed below. In general, the properties of the materials produced by both methods are much the same. For example, Agaskar described the use of several novel polyhedral silsesquioxanes as precursors to microporous organolithic materials . His approach was to synthesize functionalized polyhedral silsesquioxanes (equations 41 and 42)136. 

A foam is a colloidal dispersion in which a gas is dispersed in a continuous liquid phase. The dispersed phase is sometimes referred to as the internal (disperse) phase, and the continuous phase as the external phase. Despite the fact that the bubbles in persistent foams are polyhedral and not spherical, it is nevertheless conventional to refer to the diameters of gas bubbles in foams as if they were spherical. In practical occurrences of foams, the bubble sizes usually exceed the classical size limit given above, as may the thin liquid film thicknesses. In fact, foam bubbles usually have diameters greater than 10 pm and may be larger than 1000 pm. Foam stability is not necessarily a function of drop size, although there may be an optimum size for an individual foam type. It is common but almost always inappropriate to characterize a foam in terms of a given bubble size since there is inevitably a size distribution. This is usually represented by a histogram of sizes, or, if there are sufficient data, a distribution function. 

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