Polymers containing clusters

C. Polymers Containing Boron Clusters in the Backbone or in Pendent Groups... 

The 0.1% polymer derivative contains about one molecule of pyrene per macromolecule, whereas the 5% one has 50 to 60. The distribution of ligand on the polymer is at best binominal.42 Thus a significant fraction of the former derivative contains two to five molecules of pyrene per macromolecule. It is surprising to find excimer formation in the 0.1% derivative since so few molecules are on a single polymer chain. It seems apparent, therefore, that in aqueous solution these moieties on the polymer are clustered in the ground state so that excimer formation is facilitated. 

The step-growth polymerization strategy used to incorporate metal-metal bonded units into polymers can also be used to incorporate metal clusters into polymers. One of only a few examples of this type of reactivity is shown by equation 11.35 It is noteworthy that metal clusters also undergo photochemical reactions.36,37 These reactions should also occur when the clusters are incorporated into polymer backbones. If polymers containing metal clusters can be shown to have unusual properties or applications (photochemical or otherwise), then the synthesis of these polymers will likely burgeon in coming years. 

The compound Mo MogFe contains linear polymers of cluster spheres in which 6 out of the 30 Fe positions in Mo72Fe30 are replaced by effectively diamagnetic Mo positions.41 The relative positioning of these Mo sites can take on a variety of scenarios from a purely statistical distribution, with the six nonmagnetic positions evenly distributed over the icosidodecahedral sites, to a clustering pattern, where all six positions are situated adjacent to each other on one spot of the icosidodecahedron. 

Type III is the sorption isotherm of Flory-Huggins. Here the solubility coefficient increases continuously with pressure. It represents a preference for formation of penetrant pairs and clusters it is observed when the penetrant acts as a swelling agent for the polymer without being a real solvent. An example is water in relatively hydrophobic polymers containing also some polar groups. 

No exchange may take place when the metal is coordinatively unsaturated. Excluding metal powders, treated in 5.8.2.12.1, there are many salts that easily add CO. The coordinative unsaturation may be hidden, the metal salt being solvated by solvent molecules or existing as a dimer, polymer or cluster. The metal salt or complex can also contain bidentate or polydentate ligands or anions that leave a coordination site free for CO addition. 

Covering many areas of chemistry with boron at its centre, topics include applications to polyolefin catalysis, medicine, materials and polymers boron cluster chemistry, including carboranes and metal-containing clusters organic and inorganic chemistry of species containing only 1 or 2 boron atoms and theoretical studies of boron-containing compounds. New materials with novel optical and electronic properties are also discussed. 

Tphe phenomenon of ion clustering in polymers containing ionic co-monomers has received considerable attention recently, primarily in materials based on styrene, ethylene, or butadiene backbones containing a small concentration of pendant carboxylic acid groups randomly distributed along the chain. These materials have been reviewed in two... 

Polymers containing aryl groups also react efBdently with metal atoms to yield bis(arene)metal(0) complexes within the polymer chain . Thus, poly(methylphenyl-siloxanes) react at 0°C as a liquid with Ti, V, Cr, Mo and W atoms to give high yields of colored bis( / -arene)metal complexes. In contrast Co, Fe and Ni atoms )deld only metal slurries. Similarly, poly(oxyphenylene) and polystyrene (in a solvent) react with V and Cr atoms to yield colored solutions . By adjusting the metal-atom flux, small, polymer-supported Ti and Mo clusters can be prepared . In some cases the com-plexed metal atoms spontaneously migrate through the polymer fluid to form dimers . 

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